[jeeva]

Originally Posted by Samurai

Old radiator? This is a different Jeep. This civilian 1997 MM550 came with the XD3P and coolant based radiator. Not oil cooled, think not.

BD sir was talking about the Oil cooler, I guess. The army 550s have an oilcooler, on which the oil filter sits. Coolant/water from the radiator passes through the oil cooler and helps cool down the engine oil faster and thus its rated 500 rpms or so, more than the civilian xd3p without oil cooler.
If the jeep has a stock radiator, then chances are that with the A/C it may overheat. A custom radiator (copper) with more cores or the one which came on the Bolero would help things.

[Samurai]

So oil cooler is a separate attachment to the engine, located below the oil filter. Never seen that myself, so I don't have any idea. Mine is Civilian MM550, so it won't have it.

[Jaggu]

Nope this vehicle will not have oil cooler Samurai since its civilian. I would suggest checking radiator and getting it cleaned if the spec/capacity is ok for the set up. Otherwise i would suggest you to go for an upgrade like Jeeva suggested. Its always a pain to get the heating issue sorted in a jeep, best way is to increase the cooling capacity through an upgraded radiator. Your mech would definitely know how to go about. For now keep an eye on the temp and drive and after the A-OTR plan for an upgrade. ie if you dont have the time.

[Samurai]

If I keep the AC at minimum setting, it keeps the cabin sufficiently cool and temp stays within 90C. Also the AC switch keeps turning on and off by itself at minimum setting. I am not sure whether it is loose connection or automatic climate control.

BTW, the 4WD lever got fixed. The mechanic said the problem was with the shifter and not the gears. Now the shift stays at 4L and doesn't snap back. It doesn't have any play either.

There is grinding noise in 3rd or 4th in 4L. Mechanic said my 4WD needs an overhaul. May be after the OTR we can address that.

I did some basic obstacles in my office backyard. It was very effortless, the engine hardly strained itself.

[svsantosh]

When you are back in manipal after BAOTR, get the radiator rebuilt. 1st check with Vivek if he rebuilt it, else just go ahead with it. The top and bottom of the radiator will be torched welded out of place and all cores washed in acid and will be squeaky clean when put back together. But before removing the radiator, run it with FLUSH (bardhal) and them discard all existing coolant - rebuild radiator - and refill with a slightly higher coolant/water ratio.

My AG with FULL speed AC + No thermostat + Rebuilt 3 CORE (like urs) Radiator takes a LOT of time to reach the half way mark on temp (80') in fact I dont remember the last time in 1000' KMS it touched 80'.

While running regular highway runs without AC, it struggles to get off the BOTTOM mark which I know about the amino acid on cyl walls etc, but my engine is dead and I am happy to make it last a bit longer...

PS - Hope you read about my recent engine oil flush story? Since yours is new/rebuilt IIRC, you can keep the flush for once a year may be?

[Tejas@perioimpl]

Samurai, remember the heating issues with my classic? Behram had made me change the radiator cap. Check my thread for details.

[Samurai]

Originally Posted by svsantosh

When you are back in manipal after BAOTR, get the radiator rebuilt. 1st check with Vivek if he rebuilt it, else just go ahead with it.

I remember him saying it is rebuilt.

Originally Posted by Tejas@perioimpl

Samurai, remember the heating issues with my classic? Behram had made me change the radiator cap. Check my thread for details.

I have a big heating thread myself. Done all those measures before. I don't have heating problem if AC is off.

http://www.team-bhp.com/forum/techni...blem-jeep.html

[Tejas@perioimpl]

Have you installed a larger pulley to work the compressor? In my classic, the larger pulley installed for the power steering sucked valuable power and thus the extra strain on the engine and therefore the overheating as we'll.

[ex670c]

Hi Sharath,

Please get a thermostat fitted in the water pump.

The purpose of the thermostat is to maintain optimum engine temp, and prevent flash heating and hot-spots in the engine head.

A lil trick to improve the cooling with the thermostat is to drill 4-6mm bypass holes in the thermostat (bracket holding the wax capsule)

Regards,

Arka

[Samurai]

Yesterday, I drove the MM550 to Bangalore. I must have checked the temp gauge 400times in 400kms.

Until I hit the ghats, I kept the AC on at minimum settings, but only 50% of the time. Every time the needle came around 90-95C, I switched off the AC.

Once I started climbing the 50kms long ghat road, things changed. It started heating faster, AC time reduced. Eventually I stopped using AC entirely. Still the temp continued rise. After 75% of ghat climb, the temp sensor reached the red mark (100C) even without AC. I stopped and kept the engine idling, hoping that the continued water circulation will cool it. It didn't. After few minutes, I switched off, waited 20 minutes. When I started again, the temp was back at the red mark. That didn't make sense, no cooling after 20 minutes of wait?

So I decided to cautiously drive again, but without straining the engine. As the wind started hitting the radiator, suddenly the needle started to drop. I continued like that and finally reached Sakleshpur and took lunch break. That was the end of Ghat section.

When I started off after lunch, it was like a different Jeep. I could drive much faster now, and with much faster wind hitting the radiator, the needle took a long time to reach 95 mark. In the next 120kms of straight and fast roads, I could use AC almost continuously without fear of heating.

After the next break, I had to turn on the headlights, that is 200W of additional load. The engine started overheating again, but not to the extent of the ghat roads. In the last 110kms, I used AC 80% of the time.

So, I definitively have a heating problem. I am actually relieved. This heating problem is not because of the additional load of AC. That means, once I fix the heating problem, AC should be able run non-stop.

Originally Posted by Tejas@perioimpl

Have you installed a larger pulley to work the compressor?

No, the large pulley is left untouched. We can't use it for the fan either, it will foul with the compressor belt.

Originally Posted by ex670c

Please get a thermostat fitted in the water pump.

The purpose of the thermostat is to maintain optimum engine temp, and prevent flash heating and hot-spots in the engine head.

Ok, but I better wait until the heating problem is solved. Right?

[dhanushs]

Originally Posted by Samurai

After the next break, I had to turn on the headlights, that is 200W of additional load. The engine started overheating again

200W load on a diesel engine is nothing. It is not significant enough for the engine to overheat.

Usually, bad wiring(earthing) in Jeeps cause this. When the headlights is switched ON, the temp meter goes up. If you want to confirm, when you feel the engine is overheating due to the lights, switch them OFF (even park light) and check the temp meter. It will reduce instantly. Which means, its an earthing problem.

EDIT: One more bad earthing symptom is Fuel meter coming down when you switch headlights.

EDIT 2: Did you change the pulleys? Is your Jeep still heating up?

[Samurai]

Originally Posted by dhanushs

Usually, bad wiring(earthing) in Jeeps cause this. When the headlights is switched ON, the temp meter goes up. If you want to confirm, when you feel the engine is overheating due to the lights, switch them OFF (even park light) and check the temp meter. It will reduce instantly. Which means, its an earthing problem.

You are probably on the right track. I noticed another thing that made me suspect some electrical problem.

When I turn on the AC blower (LO), the temp needle jumps by few degrees. If I change to ME, it jumps by few more degrees. If I change to HI, it goes up again. And it comes down the same way as I decrease the fan speed. Clearly, it is not indicating the real temp. This is some electrical issue.

Originally Posted by dhanushs

EDIT: One more bad earthing symptom is Fuel meter coming down when you switch headlights.

Didn't notice fuel gauge, very hard to see it since it is hidden by the steering. Also, fuel gauge light is not working.

Originally Posted by dhanushs

EDIT 2: Did you change the pulleys?

No, I already answered why.

Originally Posted by dhanushs

Is your Jeep still heating up?

[Sutripta]

^^^ (refering to Dhanushs post)
+1

In R&D mode, better to jury rig one of the old Xylene temp gauges. (If you can get one). Bench check calibration before taking decisions based on its readings.

I have some (uncomplimentary) thoughts on a fan between the condenser and radiator, but will wait for the experts to comment. (Incidentally, I had an Armada Grand 4x4, and it did not have a OE electric fan. It must have been introduced later, in which case I'm sure BD would have an enlightening story about it.)

Regards
Sutripta

[dhanushs]

Originally Posted by Samurai

No, I already answered why.

Sorry, let me rephrase.

Did you change the belt to the smaller pulley?

[oldmonk]

Originally Posted by Samurai

Yesterday, I drove the MM550 to Bangalore.

On our way to Mangalore yesterday, the wife and I saw your Jeep (she said "Thar?", I said "offroader..") near CR Patna. It looks great, congrats!