1987 325i running hot under load

[manvell]

Hi guys - I'd really appreciate some useful input here...

The car runs hotter than it should, particularly at speed. It is also low on power, except when the engine is cool. The plugs have only a few deposits and don't have that healthy choccy brown/grey colour (but are correctly adjusted).

The injectors have been cleaned a couple of times via Comma detox fuel addative. Tappets have all been set. Brakes not binding. New thermostat. Radiator flushed out. Water pump quiet (doesn't appear to be misbehaving).

All of this looks to me as thought the car is running weak. The mixture was tested at idle but this doesn't really tell me anything about how things are when the car's being driven.

Is there anything I can test other than get the car on a rolling road and tes the mixture under load?

What could it be? All the plugs/combustion chambers appear to be the same and the running isn't lumpy but may be a bit rougher than ideal (car has 159k though).

The only other thing it could be other than fuel is ignition. The car isn't chipped. Can old/aged HT leads or weak coil give these symptoms?

Thanks in advance.

[Gwynleym10]

I think timing can cause this, but not sure if it is ajustable on m20s ?
But it also could be a cracked head, pretty common problems on m20s.
Are you loosing coolant?
Maybe get a compression checked as well then


Welcome to the zone by the way.

[E30BeemerLad]

mine is starting to do this, usual running temp is between 1/4 & 1/2 on the gauge, noticed at prolonged motorway cruising at 80+ that the gauge creeps to just over 1/2. If I slow to 70 then after a mile or so the gauge goes back to normal. It is fine on normal urban driving.Just goes up if I give it some welly, which is often!

I have a headgasket problem which I am going to sort in the next few weeks. It started dumping coolant out the expansion tank breather pipe when the car was switched off when hot. Put some additive in the coolant Kalimex K-Seal www.kalimex.co.uk and this has kept it from losing coolant but the system still seems pressurised, so I look upon this stuff as a temporary repairt to be honest.

Do your coolant pipes feel rock solid?

I think you may need to look into checking if it is a head/headgasket problem.

Let me know how you get on.

[manvell]

Guys - thanks for the input.

One of my first thoughts was that the head was porous (a common problem on old M20 engines I believe) but the coolant levels are not dropping and the oild filler cap is clear of milky stuff even after a couple of thousand miles).

Also, I've just checked the compression and all pots were 13.5bar with the engine hot except cylinder 5 at 12.0 which I was able to put down to an incorrect exhaust valve clearance. I may be wrong about this however.

It could well be the head, but none of the supporting symptoms are there.

I want to try a chip (Zone1) from Ant so may just see what happens with that.

Also, is it possibly the air flow meter? The throttle body hose was split for a while and the inside of the old pipe was wet/filthy from dirty air breathed from the engine bay over the winter. If so - can it be cleaned? A wash in petrol perhaps....

Thanks again.

p.s. one tank 240miles at 80mph easy driving....

[Fushion_Julz]

Suggest you check the radiator and thermostat....

sounds like a rad core problem