Question
-------------------------------------------
The text above is a follow-up to ...
-----Question-----
For 11 months I have been trying to have my overheating problem fixed on my '97 3.9 litre Disco. Overheating happens when the car is under load, ie up hills or towing, aircon on, fine when driving on a level road.Already done is 2 water pumps,viscous coupling,several thermostats, several expansion bottle tops, new radiator, cylinder head off twice, engine removed to pressure check for cracked block, engine and block ground timing checked, vacuum advance checked. The latest research done was with an infra-red thermometer giving point temperatures on the surface of the engine. Basically the outcome of that is that the 4 cylinders on the left side were +- 100deg C and on the 4 on the right side were +- 140 deg c. I would assume that the left is correct and the right incorrect. Can you help?
-----Answer-----
Hi Mike,
who is doing the work? Temperature imbalance is a concern as it indicates flow restriction or engine distress.
You've almost rebuilt the cooling system.
What else increases heat? Lack of lubrication. Transmission or engine friction.
Sticking exhaust valves can result in a loss of power under load and may increase engine heat.
Has anyone inspected your valves?
Most series II have sticking valve problem and a valve job is the only fix. The series I can also have this problem but usually it's able to force it's way thru this. Not having the advanced BOSCH ems, the series I can manage but there is a loss of power. Maybe heat and premature wear of pistons in one bank is the next step in this decline.
Best of luck,
JohnMc
What
My local mechanic is doing the work. He has 40 years experience and was the service manager for BMW for many years so I feel he is very competent. Insofar as specialist work is concernened the heads and block has gone to the most highly recommended, well equipped factory around (incidently when the pressure tests were done they were done at 98deg C).
Air conditioning also causes the problem. Yesterday I drove the car for some 50 miles to the cooling/radiator specialists, driveing very gently, outside air temp +-23 deg C, aircon off and there was no overheating. I am certain that had I switched on the aircon and driven normally there would be some overheating on the hills.
The head has been rebuilt with the valves re-seated.I think the significant point is that all those 4 cylinders are 40 deg C high, not just one or two.
There is no loss of power and the engine otherwise runs fine.
Thanks
MIKE
AnswerHi Mike,
wow...there's not much left to be done. Trouble is...you still have the problem. I spoke with a friend whom I trust to work around my Disco. He read your comments and suggests some areas to consider:
First, he asked about oil condition. If your oil was old and has sludge, it's possble that improper lubrication could do this. Perhaps an engine oil flush is needed.
He ruled out an air pocket in the cooling system. So much work done should have cleaned this up.
It could be exhaust related. Fouled manifold, cat, exhaust pipe could cause overheating.
He seems to think that if a sensor is faulty, you could be having fuel mixture problems - perhaps too lean on the one bank. If a sensor is not working properly, it may not indicate a lean mixture, especially under load (uphill) and thus the bank of cylinders would be under duress.
The other possibility could be ignition timing needs adjustment.
I hope this helps,
Regards,
JohnMc
He seems to thin
