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Old 1st September 2011, 20:37   #1
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Default Mitsubishi Lancer: Loss of engine compression

Hi,
I drive a 1999 model petrol Lancer which has done approx. 95,000 km. This car has been in the family, here in Delhi for over 6 years now and has been well maintained and carefully driven, it has done a genuine 37k km in those six years. It was bought used in 2005 with around 58k on the odo.
I recently took the car for an engine scan and a compression test and was shocked to discover that there was serious loss of compression in all 4 cylinders.
The compression figures were around 82-90 psi across all the cylinders!! That's a BIG loss, and the mechanics immediately pronounced the pistons to be bust, but i couldn't figure out how that could happen in just 95k kms. There are no tell-tale signs of engine damage - no blue or white smoke at all, no excessive oil consumption, (in fact, the car has hardly used up any oil in the 7000 km since last service) the spark plugs were fairly clean so I really can't figure out what could really be the reason for the compression loss. The only issues are a low (sometimes unsteady) idling speed and subsequently a slight juddering when first moving on a cold engine, and of course, a noticeable power loss at low revs. There is a slight hissing sort of sound when i lightly rev the engine while moving, and someone suggested that it could be a valve problem, maybe the exhaust valve. All mechanics say the same thing - that the pistons are gone and the engine needs a full overhaul. But that's a big expense and i need to be doubly sure that it's the right diagnosis.
Right now, i'm a fairly stumped.
Anyone ever had a similar problem? Do you think it's definitely the pistons gone kaput, so early? I could really use your thoughts or advice on this problem.
Also if anyone can suggest a good place here in delhi that i can take the car to for a proper check, apart from the HM authorised service centres.
Thanks in advance..
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Old 1st September 2011, 21:01   #2
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Default Re: Mitsubishi Lancer: Loss of engine compression

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Originally Posted by jerry can View Post
.
The compression figures were around 82-90 psi across all the cylinders!! .

Did they disconnect the fuel pump while taking this reading? The normal reading should be 150-160 PSI, check it again after disconnecting the fuel pump, a conventional scan gauge never gives accurate readings.

Please feel free to contact me if you have any further questions.

Pramod
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Old 1st September 2011, 22:11   #3
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Default Re: Mitsubishi Lancer: Loss of engine compression

Could be
(A) compression leakage past piston rings
(B) compression leakage past valves.

Inject 20 ml of gear oil into each cylinder through the spark plug opening, and recheck compression. If compression improves you need new rings / reboring. If compression doesn't improve, you have leaky valves.

Also, as pramodkumar suggested, the fuel injection pump need to be disconnected and the fuel feed pipes plugged before checking compression.
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Old 2nd September 2011, 04:17   #4
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Default Re: Mitsubishi Lancer: Loss of engine compression

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The compression figures were around 82-90 psi across all the cylinders!!
That is a massive reduction in compression buddy.
One more possibility for low compression, worn our gudgeon pin or the needle bearings or the wear in gudgeon pin hole (in piston) This reduced the piston travel (from BDC to TDC) resulting more volume left at the end of compression stroke. Final outcome, poor compression.

Have a detailed check before the engine dies completely. Keep us updated.
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Old 2nd September 2011, 23:46   #5
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Default Re: Mitsubishi Lancer: Loss of engine compression

Simple test. Run the car till ideal temperature. and rev hard. See if you can see white smoke. Its a tell tale sign of piston rings giving up.

Do a compression test like SST suggested above, with and without oil from a competitive garage. You live in the world's best juggad city. Check tbhp directory for competent garages.

Its a '99 car that has run almost 1 lac kms, the power loss is inevitable. are you planning to keep the car for long, if not I would not suggest you for an overhaul.
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Old 3rd September 2011, 03:33   #6
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Default Re: Mitsubishi Lancer: Loss of engine compression

Thanks Pramod, SST, Mr. Boss and SirAlec. Really appreciate your advice.
Now i think i'll go hunting for a competent garage where i can all the tests you've mentioned, done properly. I might bother you guys again as soon as i get some results.
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Old 3rd September 2011, 20:13   #7
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Default Re: Mitsubishi Lancer: Loss of engine compression

most probable reason is worn piston rings. Once they heat up the engine will run fine.

Another reason may be worn valve guides so that the valves stick when engine is cold, again this will disappear once the engine is hot.

As suggested
. Block the injectors and check the compression
. Then squirt some oil into each piston and check

If possible perform the check both with cold and hot engine. I have a compression tester lying some where, will have to search as have not used it since twenty five years, then if you want we can check the compression.
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