[FlatOut]

As engines have become more complex they also generally have become more long-lived. As a simple example, petrol injection with electronic control has reduced the problem of bore wash and electronic ignition control prevents wear occurring through incorrect ignition timing. Since diesels have always had fuel injection (which is also the ignition timing) they were traditionally longer lived than old-fashioned petrol engines.

So instead of wondering when it is time to overhaul an engine, as has been detailed very well in all the posts above, maybe it is of interest what you can do to prevent an engine rebuild? Over many tens of thousands of hard miles, I have never had to take an engine apart to repair it, even though mileages have often exceeded 200,000.

Always use the right oil and recommended filters. Change them at the suggested intervals, or well before if conditions are harsh - very hot, or dusty, for example. If unsure of fuel quality, change the filter as often as you think fit and make a habit of draining water from the drain tap - for loose change you may well save the engine, especially if it is a diesel.

Don't overrev an engine beyond its limits, have some mechanical sympathy, so no high revs from stone-cold, allow a turbo to cool over the last couple of miles with gentle driving at medium revs if it has been working hard, never allow an engine to overheat - this is almost guaranteed to kill it - and if it spends its life at low speed then drive it relatively quickly on empty roads every fortnight or so, to keep the combustion chambers clean.

Change the cambelt with a high quality item together with any pulleys and tensioners which make it work. If a failed water pump can break a cambelt, replace that before it gets too worn and old. Make sure the radiator isn't leaking, use the correct mix of coolant to water and replace this as often as the manufacturer says. Diesel injectors tend to 'break' before/as they wear on CR diesels, otherwise with a proper old-fashioned diesel check them for wear at 100,000km. Poor spray patterns can prematurely wear bores.

In short, follow the manufacturer's recommendations, and change the oil every 10,000km max - no matter what they suggest. I avoid semi-synthetic oil - a friend in the industry told me I was better off with a good quality mineral oil since semi-synthetic is cheap mineral oil with an extra syntheised additive package. In contrast, fully-synthetic oil is the business, but pointless on many regular engines if you are using oil to the suggested quality and changing it regularly. Check the oil level every fortnight. Be aware that some manufacturers (for example, VW group) use very hard piston rings which take longer than many to bed in, so oil consumption can be high before this has taken place. Don't let a new engine run low on oil. But be aware that over-filling the oil can as much damage as letting the level drop too low.

If air filters are very clogged when you change them, increase the frequency with which they are replaced to suit. Beyond this, there isn't a lot you can do, beyond get bored with an engine which continues to run as well as the day it was run in. Sort out any little issues before they can do damage.

[kraft.wagen]

Help!!!
I have a 2001 Zen, which is clocked close 120k kms. The car has been idle for the past 3 months and today when JD(my driver) took the car the engine had a strange noise. The noise increases when accelerating. When the car was taken to the MASS the service person said that the engine needs a over haul and it would take approximately 10-12days with a cost of 30-35k.

Is this normal, the number of days to overhaul an engine? Should I check out local mechanics?
What exactly is going to be done as part of the overhaul? I'm thinking its a whole re build if they need the quoted 10days. Is it worth investing so much time and money?

[V-16]

I read this thread and wondered, hey, why didnt i ever think of asking that or even trying to find an answer to that question ever? Not someone who is very technically inclined, I took this question to my good friend Mr. Mechanic and made it clear to him that i wanted an answer to my questions and not in some terms which i didnt understand. If the terms were necessary, he would have to explain them to me. He being a patient and understanding person, took me to his office/cabin/store, ordered a cutting chai for me and explained in the following way which i will try and repeat;

He started by explaining why engines need to be overhauled/rebuilt. We all hear of an overhaul or a rebuild but what does it mean?

There are parts in an engine such as the Connecting Rods, Pistons, Crank Shaft, etc, which move constantly in a working engine with the help of bearings. These bearings are of various types and require lubrication to move freely and constantly which is provided by the Engine oil, available in various grades according to the engine capacity. When the oil levels are not maintained properly in the engine, it gets low and the lubrication gets minimized, hence these parts cannot move freely and friction sets in thus accelerating the wear and tear many fold and leading to damage of these as well as other related parts. This happens due to negligence or ignorance. Every part has a life, it cannot go on forever, hence therefore one must maintain ones cars regularly, which means checking the oil levels and other lubricants for starters. If not maintained properly, these parts experience wear and tear much before they should, hence it would not be right to say that in X kms an engine should be overhauled and so on.

As parts, even the lubricants have a life span and should be changed according to the specifications mentioned by the manufacturer, or if tell tale signs appear such as thickening of the oil or dis-coloration or getting creamy and sludgy.

He asked me if i had experienced a knock in any of my cars recently. I said thankfully not. He went on to explain what created the peculiar pinging sound we call as a knock. Worn bearings are what cause this sound he said and the louder it gets, the more your engine needs work on. Eventually if not treated, this can lead to engine seizure.

Every Piston has a Piston Ring which is fit onto groves on the side of the head of the Piston, working to seal in the gas created in the engine due to the burning of petrol. As Piston rings wear, their sealing properties start wearing off and they allow leaks which leads to the crank case oil finding its way past these worn rings and burning with the fuel and air mix in the cylinder. This is called a Blow By. This also causes greater smoke emission. So one must be on the lookout for Knocking or/and excessive smoke being emitted by the car or even simple ones like your car just wont start with just a crank, u need to crank it many times around or the car doesn't feel to have the power.

You feel the car is running sluggish. Again, just because your car has these signs does not mean your engine needs to be rebuilt, it may or may not need the full monty treatment. Knocking tells you that theres something wrong. If it gets louder with acceleration, it tells you there is something more wrong than usual and can lead to a blown head gasket and probably a cracked head. If it is continuous with a loss of power then there the wrong has gotten or can get serious

Just then, a 12-13 year old boy wearing overalls two sizes large, with grease and oil stains on them ran into the cabin with two small plastic cups (approx 25 ml each) and a plastic packet with tea in it, tied in a secure knot. He whipped out his pen knife and poked the top end of the bag making an incision in it, overturned the bag and gently squeezed the tea from the plastic bag into the two cups, without spilling a drop. ingenious i thought.

My mechanic then leaned back into his chair, which was a leather covered driver's seat from a Tavera and explained further, the reasons for an engine rebuild ,and tell tale signs in between sips of the overtly milky and sweet tea.

SMOKE:

Different colours of smoke emitted can mean different things. It basically tells you whats going on inside the Engine.

Excessive and continuous White smoke from the tailpipe will tell you that in all probability you've got a blown head gasket or a damaged cylinder head. That means that somehow water/coolant has found its way and entered the combustion chamber. This could have happened when you drove the car with low or no coolant and with the engine running hot the head gasket got blown. To ensure, check your engine oil dipstick and oil filler cap. If it looks unlike the oil you put in there or is a creamy muddy colour thick mess, there's water/coolant in your oil. Let the engine cool and check the coolant level in your radiator. It's probably going to be low. In that the case, you need to check the cylinder head determine the extent of damage and then, repair.

Blue smoke tells you, you are burning engine oil. Oil is somehow getting past sealants and this is due to excessive wear or damage or something inside is broken and not doing what it is supposed to. One has to determine whether the damage is on the head or the block or both. On the Top end it may be Valve guides or just worn out seals. The bottom end can be more serious because it may be related to damage to the Pistons. This is usually more expensive. Check for Oil consumption in case of blue smoke and more often than not, you will notice that the intervals between topping of engine oils have decreased, that is if you are checking your oil levels. The lesser the top up times, the greater the problem. Take it to a mechanic immediately and dont plan on any trips unless you get the engine checked..

Black smoke tells you the fuel mixture is rich. This means you need to tune the engine and control the fuel and air mix that enters the combustion chamber. This kind of smoke is not as serious as the top two but if let loose it may lead to further damage leading to more expenses. Of course black smoke also may mean serious issues but if that is the case you will know or rather hear it so when the engine smoke gets black, get the fuel-air mix checked and corrected, which may mean just a correction or repairs to the parts that lead to this.


POWER LOSS LOWERED ENGINE PERFORMANCE AND STRANGE NOISES:

"You will just feel the difference" he said. The car just doesn't move like it used to, there is some kind of sluggishness to its movement, it feels chocked. If the power loss is not sudden or immediate then thats because over the years and running for hundreds of kms, it is bound to happen because of the normal wear and tear but if this occurs suddenly then theres a problem which needs to be addressed ASAP. The noise may be a bang which is a misfire and may be a continuous grind or irritating but rhythmic tapping. Usually the noise gets louder with acceleration of greater load on the engine. This may also be accompanied with strange noises or sounds and the louder these sounds, the quicker the car needs to be taken to the garage, preferably towed there to avoid any further damage


He then explained what Happens in an Engine Rebuild.

When an engine is rebuilt, means its made almost as new. The top and lower ends of the engine are removed and separated. More often than not, even the cylinder head is worked upon to get the maximum out of the newly rebuilt lower end. Depending on the damage which is acute (thats why the engine is being rebuilt in the first place) the engine is disassembled and cleaned so that the condition of the block and head can be can properly assessed. Then the parts which need to be replaced are replaced or repaired as the case may be and the internal surfaces of the cylinders are reconditioned if not acute or a sleeve is added to make them smooth to ensure that the new piston rings form a proper seal with the cylinder walls. The engine is then reassembled, checked for compression and installed back in the vehicle.

Having got a clear picture now, i headed back to my home and immediately vowed to look after my cars in the way he had explained. I hope i could explain to all of you how he did to me. I am better educated now and look at my car as not just four wheels to take me from point A to point B.

If there are any more questions, i will gladly take them to my mechanic for an answer. Im quite addicted to that sweet milky tea he offers me everytime i visit him.

[saket77]

Originally Posted by V-16

Not someone who is very technically inclined, I took this question to my good friend Mr. Mechanic and made it clear to him that i wanted an answer to my questions and not in some terms which i didnt understand.

That was fantastic explanation Sir! And if its all true what you wrote, then you are blessed with a very nice, knowledgeable & patient person to be on your side whom you can trust for the critical jobs. Very nicely written too, in layman terms!

Thanks,
Saket

[Sutripta]

Originally Posted by V-16

He asked me if i had experienced a knock in any of my cars recently. I said thankfully not. He went on to explain what created the peculiar pinging sound we call as a knock. Worn bearings are what cause this sound he said and the louder it gets, the more your engine needs work on. Eventually if not treated, this can lead to engine seizure.

Hi,
Lots of not quite correct explanations, but the one quoted above is very wrong. Time for you to educate your mech!

Regards
Sutripta

[FlatOut]

Sometimes a little knowledge can be a dangerous thing... trying to put into a few words the description of different sorts of wear or damage in an engine can misleading to the uninformed. I knew someone who once took an engine to pieces because it was knocking under load, couldn't find anything wrong, rebuilt it, sound still there - it was a loose bracket under the bonnet. There are many knocking noises which may sound like engine bearings, which may be anything but. A car is full of scores of moving parts. Some mechanics like to pull engines apart rather too quickly - it is all good work...

Some engine bearings can go quiet under load, only to become noisy when there is no load - ie not accelerating or decelerating. Poor fuel can cause an engine to knock or ping. Some can make noises which sound nothing like a knocking. It is not an easy matter to discuss or explain on paper. An engine which is pressurising/excess blow-by, blowing blue smoke and/or down on power may not have worn bores or rings - and may be cured within half an hour with a few 'tricks of the trade'.

People seen quite keen on concentrating on having their engines overhauled - the preferred approach here in the UK is to buy a second-hand engine and have that fitted, since modern engines with modern lubriucants rarely wear under 200,000km if maintained properly.

It's important to point out that taking an engine to pieces and rebuilding it with some new parts often means it often won't run as sweetly as originally and that many parts used aren't as high quality as the originals. Japanese engines in particular don't take kindly to being rebuilt - they are beautifully assembled at the factory. Such are the tolerances of all modern engines that many main dealers are required to send any damaged engines back to the factory to be rebuilt, they then fit one back from the factory.

Hence my emphasis on looking after your engine as I described above. There are very few engines which are so badly designed they just wear out for the sake of it. Not replacing engine oil every 6 months or 10,000km is a major cause of premature wear. So is not using the right oil. And if you don't replace the fuel, oil and air filters when they need it, you are courting disaster!

The manufacturers' recommendations will often state a given service interval, then cover themselves with words to the effect of 'or at half that interval under harsh conditions'. If there is much dust in the air, if it is very hot (above 30C) or you do lots of short journeys, then I would term that harsh conditions. Oil and filters are cheap compared with engines.

V-16, if you have any more questions, I can't offer you any tea unfortunately, but I have rebuilt many engines in the past - as well as having diagnosed problems which seem like a damaged engine but which are in reality something much simpler.

[Jeroen]

Originally Posted by FlatOut

Hence my emphasis on looking after your engine as I described above. There are very few engines which are so badly designed they just wear out for the sake of it. Not replacing engine oil every 6 months or 10,000km is a major cause of premature wear. So is not using the right oil. And if you don't replace the fuel, oil and air filters when they need it, you are courting disaster!

I agree! Just stick to the basic prescribed maintenance by the manufacturer and that will ensure you won't need an engine overhaul in the first place.

Engine overhaul because of a noise?? I'd be very cautious and ask around for some second opinions. On modern engines it's very rare. Most relevant reason for an engine overhaul is loss of compression, which results in less performance and potentially could damage the engine some more, due to unbalance.

If your engine uses a lot of oil? Check compression/blow by. If that's ok, why bother, filling a liter of oil every 500 kilometer is a lot cheaper then overhauling an engine.

Swapping an engine as pointed out is often much easier, quicker and a lot cheaper. Overhauling an engine requires in most cases special knowledge and special tooling. And in most cases you need to lift the engine out anyway, unless you only need to work on the cilinder head.

Classic car owners might take a somewhat different stand. When they restore a car, they might overhaul the engine as well. Even though there might not be any indications, they would consider it part of a proper rebuild. Also, when you are restoring a car and take all the bits of you might as well have a go at the engine. Also, for many classic car owners, keeping the original engine with the car is important. Properly more for sentimental reasons than anything else. Only of top of the range cars you will find having the original engine might influence the market price.

I bought my 1986 Alfa Romeo Spider from an Alfa Romeo Dealer in the Netherlands. Every year he went across the States for a few weeks, bought al the Spiders he could find and shipped them home. He would then offer the Spiders at a fixed price, no negotiation, fully restored, including a complete engine overhaul. He never even bothered checking the real condition of the engine. He would overhaul the engine, put new (high compression) piston in it, etc. etc.

In my Mercedes W123 club we've overhauled a number of petrol and diesel engines. All because of loss of compression.

Other then my company cars, I've never bought new cars for myself. I'm very comfortable buying a car with 100 - 150.000 kilometer on the clock. Especially if it was accumulated in a relative short period.

Don't know about India, but in Europe still, most people don't like to see more than 100.000 kilometer on the clock. Which means the second hand prices start dropping rapidly for these high mileage cars. If you're comfortable with high mileage cars, it's amazing what is out on the market. BMW's, Mercedes, Jaguars, Audi's etc with 150.000 on the clock 4-7 years old will cost less than a 2-3 year second hand Volkswagen Golf!


Jeroen

[FlatOut]

Originally Posted by Jeroen

Don't know about India, but in Europe still, most people don't like to see more than 100.000 kilometer on the clock. Which means the second hand prices start dropping rapidly for these high mileage cars. If you're comfortable with high mileage cars, it's amazing what is out on the market. BMW's, Mercedes, Jaguars, Audi's etc with 150.000 on the clock 4-7 years old will cost less than a 2-3 year second hand Volkswagen Golf!
Jeroen

True, although in Britain those in the know have totally changed their ideas of a high mileage car. Twenty years ago, 100,000 miles was treated as junk, maybe good for a few panels and trim. Most Fords and other indigenous cars were utterly worn out by this point. This attitude encompassed all cars, so that when the better continental European makes were being sold with such a high mileage, they were similarly valued.

Slowly attitudes have changed, as more and more people managed to buy bargains with 'starship' mileage on them. If you buy a good design of car, then 100,000 miles is just nicely run in. My old diesel Mercedes, the Audi 5 cylinder diesel and various pre-historic Citroëns from the 1970s are going beautifully beyond 400,000 km, burning no oil, using no water, and driving as well as ever.

People's attitudes need to change - good engines only fail on the wrong side of 150,000km if they have been seriously neglected or abused.

[IndigoXLGrandDi]

Originally Posted by V-16

Black smoke tells you the fuel mixture is rich. This means you need to tune the engine and control the fuel and air mix that enters the combustion chamber. This kind of smoke is not as serious as the top two but if let loose it may lead to further damage leading to more expenses. Of course black smoke also may mean serious issues but if that is the case you will know or rather hear it so when the engine smoke gets black, get the fuel-air mix checked and corrected, which may mean just a correction or repairs to the parts that lead to this.

How to get fuel-air mix checked and corrected in Common Rail Diesel Engines (Xylo E8 ABS run 176KKms) since it is controlled by ECU?

[V-16]

Guys we are discussing here about when is it time to get an engine rebuilt. While there will always be a few who will dismantle an engine for the sheer sound of a knock, most of us would like to study, get a second or even a third opinion if needed and then get into the rigmarole of an overhaul, as the last step to be taken. Therefore it is to be presumed when suggesting probable causes, that the engine is seriously suffering from these ailments. Of course that is after taking the precautions of eliminating the milder reasons of the symptom. I think we are here to discuss, where the engine should be rebuilt as a last and sure option, taking all possible caution not to be mislead. So please offer pointers for when such an action becomes necessary presuming that the symptom mentioned is actually present.

Originally Posted by Sutripta

Hi,
Lots of not quite correct explanations, but the one quoted above is very wrong. Time for you to educate your mech!
Regards
Sutripta

Plase read my above explanation.

I took this question to my good friend Mr. Mechanic and made it clear to him that i wanted an answer to my questions and not in some terms which i didnt understand. If the terms were necessary, he would have to explain them to me.


I think you mean that worn bearings are not the only cause of a knock Sutprita, which i agree to. We have to read the answer with the question of this thread. We all know that simple knocking does not attribute to overhauling an engine, therefore when Mr. Mechanic mentioned the knocking, he meant it to be of a serious nature, for which he gave the explanation, so in the circumstances, his explanation seems right, unless you want to say that under no circumstances does knocking/pinging (as differentiated from the knock one experienced due to wrong fuel or fueling issues [being one of many reasons]....which i any case will cause engine damage nevertheless if ignored). In any case he never meant that to be the only cause for knocking but is one of the causes for serious knocking when it is so threatening that it may hamper the engine, so i stand by his explanation!!

Please point out the other incorrect explanations also so that no one here may get mislead but please take the explanation in light with the question asked.

Originally Posted by FlatOut

There are many knocking noises which may sound like engine bearings, which may be anything but. A car is full of scores of moving parts. Some mechanics like to pull engines apart rather too quickly - it is all good work...

We can go on debating what could also not be the cause that is an endless discussion. Lets stick to the question and answer it, presuming that the noise etc is the actual reason.

V-16, if you have any more questions, I can't offer you any tea unfortunately, but I have rebuilt many engines in the past - as well as having diagnosed problems which seem like a damaged engine but which are in reality something much simpler.

Thanks for the offer.

Originally Posted by IndigoXLGrandDi

How to get fuel-air mix checked and corrected in Common Rail Diesel Engines (Xylo E8 ABS run 176KKms) since it is controlled by ECU?

This is best addressed by the company of you are running a stock OE ECU. If you have a piggyback or a stand alone ECU on the other hand, the tuner will set these parameters or if one is proficient oneself, one can set these parameters on ones own. For that one would have to have access to the tuning software of that ECU. Generally a proficient person will have an AFR (Air Fuel Ratio) meter affixed in the car to tell give him constant reading of the AFR mix so that he can always keep an eye on it. Without proficiency, o course, that piece of device is only eye candy. In your case if you have a problem (how you detected that it is an AFR problem would be interesting) the best bet would be to take it and get it checked by the authorized dealer.

[Sutripta]

^^^
In the beginning it has been stated to be ping or knock. And that it is caused by worn out bearings. In the rest of the article, the term 'knock' has been used repeatedly.

What is internationally understood to be ping or knock is caused by uncontrolled combustion setting up vibrations in the combustion chamber/ cylinder head. It does not refer to noisy bearings, or any other noise from worn parts. (OT for this thread - The shaking/ rough running of an engine due to extreme lugging is also called 'knocking' in local parlance. It is not.)

Low oil:- as long as above min level should cause no problems. And manufacturers leave quite a bit of cushion. Overfilling, on the other hand, causes a lot of trouble.

Piston rings:- Lots of thoughts. Not really for this thread.

Would like to know your mechs views on wear (if any) of con rods (not the bearings), cap bolts, and valve springs.

@IndigoXLGrandDi: AFR in diesels?

Regards
Sutripta

[dhanushs]

Originally Posted by IndigoXLGrandDi

How to get fuel-air mix checked and corrected in Common Rail Diesel Engines (Xylo E8 ABS run 176KKms) since it is controlled by ECU?

IndigoXLGrandDi, if your Xylo is emitting black smoke, please check clogged air filter, faulty turbo/plumbing.

[IndigoXLGrandDi]

Originally Posted by V-16

if you have a problem (how you detected that it is an AFR problem would be interesting) the best bet would be to take it and get it checked by the authorized dealer.

On reading the posts in this thread, I was curious on learning more about the AFR in Diesel Engines.

Originally Posted by Sutripta

@IndigoXLGrandDi: AFR in diesels?

Please go through below thread (Paragraph 7 Line 7)-
1.http://www.dieselpowermag.com/tech/g...s/viewall.html.

Therefore, the air/fuel ratio of the diesel engine must always be leaner than stoichiometric to prevent excessive amounts of smoke.

Originally Posted by dhanushs

IndigoXLGrandDi, if your Xylo is emitting black smoke, please check clogged air filter, faulty turbo/plumbing.

The Air Filter was replaced with new one @4Kkms ago.
for going OT but how to check Faulty Turbo. The Pickup and FE are good.

[Sutripta]

Originally Posted by IndigoXLGrandDi

How to get fuel-air mix checked and corrected in Common Rail Diesel Engines (Xylo E8 ABS run 176KKms) since it is controlled by ECU?

Originally Posted by IndigoXLGrandDi

On reading the posts in this thread, I was curious on learning more about the AFR in Diesel Engines.

Please go through below thread (Paragraph 7 Line 7)-
1.http://www.dieselpowermag.com/tech/g...s/viewall.html.

Interesting!
So I take it that diesels have an optimum AFR, and that in a modern CRDI the AFR is monitored and corrected when needed by the ECU.

Any ballpark figures for this optimal AFR for diesels?

Regards
Sutripta

[IndigoXLGrandDi]

Originally Posted by Sutripta

Any ballpark figures for this optimal AFR for diesels

That is what I too want to know. Hence I asked. But I corrected my question as underlined and bold-

Originally Posted by IndigoXLGrandDi

How to get fuel-air mix checked and corrected (if it is wrong) in Common Rail Diesel Engines since it is controlled by ECU?

I think the AFR varies with vehicle.
So I think the best bet would be to check with the OBD Scanner connected to the vehicle (since it has the Requisite Values preset in the software). But here one problem comes in way- The SA or WM (Works Manager) would not allow to connect OBD unless you face some True(?) problem with the Engine.