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overheated while running at idle

Hello,

My car seems to run more difficult at idle when just started. The ecu tries to rev up irregularly and sometimes the rpm gets really low for a while. When driving, fuel consumption has gone up when accelerating - which is not as vivid as before - and even at cruise is slightly higher than before.

Could this be an indication for head gasket problems ?

I will have someone check fuel system problems, but this is the story from last week.

One mechanic replaced coolant liquid by just filling up the radiator a bit with the engine at idle, and adding more at large intervals of time - instead of using the vent plug near the thermostat. The thermostat appears to have a vent hole though.

He did not drain the cabin heater as far as I know, because he added less than the total circuit content. He also used some water for flushing first, but I can't tell how much.

I wonder if a head becomes warped when the engine overheats slowly at idle ? He did not rev up until he had added more coolant and the fan had turned on. Can a head overheat and not warp ?

Still, compression tests show good values, this time when hot and full throttle, 17 bars on all fours. When measured cold and closed throttle a while ago, it was 15 bars.

Since then I read posts about oil control rings, and the above would not exclude oil ring problems and better compression values due to oil - which is consumed in a more than normal way - I sucked some burned oil out of the cylinder with a tube and vacuum.

For the rings, maybe my style of driving - very low throttle - and oil consumption could lead to other problems, I read about glazing ? I would be tempted to step on its tail and open the throttly, but the head gasket could fail ?

How can I ever tell the engine has suffered damage from overheating, except when the head gasket really blows ? Since fuel consumption has risen only a small amount, could it be ring damage ?

Puzzled & looking forward to advice,

Peter

Reply to
Peter
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You dont say what car or model or engine.

However, assuming port fuel injection, first look at dirty idle speed control.. symptomatic of 'hunting' plus occasional low idle.

If the Ford has the mass air flow (MAF) sensor, warm the car up. Stop engine, disconnect MAF connector, then start and test drive. If better, then clean your MAF; If worse, or wont run at all, You probably have another sensor problem.

Another possibility, bad fuel pressure regulator.

If the car doesnt overheat now, leave the head gaskets and rings to worry about later.

Reply to
Backyard Mechanic

Hello, and thanks for your reply !

As the problem only appeared just after the coolant change, I wonder whether fuel or sensor problems can be a cause. I observed the car the days before ( fuel consumption behaviour ) and it was very consistent. It changed exactly the day after ( when the car had cooled down). I did not fill up gas or anything.

Does overheating during a partly dry operating period lead automatically to overheating later ? I checked coolant purity and it seems fine, no deposits under the cap. I worry about head and rings regardless, would driving make things worse, especially because of the high compression values ( 17 bars ) ??

As I am not familiar with the fuel system, I will have someone check all you said. But another mechanic hooked up a diagnostic tool and said all was fine.

I noticed the radiator outlet hose is running up to about collector level and then down again to the waterpump. The radiator inlet hose is coming from the engine slightly above collector level. I can't help fearing that normally filling up such a circuit would mean engine and radiator should be almost completely full first fill, and only a slight amount would have to be added later. In my case, the engine run a long time with only half this amount. I wonder whether thermostats really have vent holes nowadays.

I imagine watching oil, coolant levels and taking regular compression readings would help monitoring head gasket problems ? Is there anything I can do aditionally ?

I drive the car very gently now, but maybe if I want to know the head gasket is fine, I should take my chances and open up the throttle ?

Thanks again,

Peter

Reply to
carl

I dont know why I am replying again since you didnt address any of my original suggestions...

But SEVENTEEN BARS compression reading?!!!!!!

At a standard (14.5) conversion, that's 246 PSI!

What model and engine is that again?

- - - - - - - But it's either overheating or it's not!

The definite answer is that gross overheat MAY OR MAY NOT result in future overheat, DUE TO blown gasket, cracked head or block. Usually NOT.. except for a few engines like the Aluminum head 3.8L... and, to a lesser extent, any cast iron block/Aluminum head engine.

So NO ONE can give you a straight answer because YOU dont supply the info... we cant even make an informed guess.

If your complaint is the idle roughness, fine - read my post again... if all you're doing is worrying about overheating in the future, just continue worrying on this thread and we'll all ignore it.

"carl" wrote in news:KZ%De.150621$ snipped-for-privacy@phobos.telenet-ops.be:

Reply to
Backyard Mechanic

Thanks for the second reply.

"Backyard Mechanic" news:Xns969B55BDA115Bpettyfogery@207.115.63.158...

I did, but cannot adress these suggestions personally. There should be other issues treated as well. And I will pass on your remarks to the mechanic, if he'll let me. My experience is some can't really stand well customers who are interested, let alone make suggestions. I did empty a tank looking for a gas station a long time ago, and maybe filters or anything else have been affected.

Could it be due only to oil presence above the oil control rings ? There is no carbon build-up.

I'm sorry to say there are reasons I don't want to mention it. The high compression was there after a power test, and it was high but not that high before. A dealer said to adress the manufacturer because this is unusual.

I vacuumed out some burned oil of the cylinder with a scraping hose and was surprised to find more in cylinder 4 than the others. But the compression is still high, although an endoscope check indicated no carbon build-up reappeared. An indication is though that a new car is consuming oil at a rate at least twice MAX-MIN between oil changes.

This is cast iron and aluminium. And there are 16 valves. If the coolant never filled the complete engine and the engine turned at idle for at least

15 minutes and then 30 minutes ( arriving hot ! ), it may result in overheating then ?

Any slight damage could push up fuel consumption ? I worry about an inconsistent change in behaviour, fuel parameters, just after this coolant event. And if it's due to head gasket damage, I worry about that too.

Yes, I'm sorry.

It is a liability problem as well as a mobility problem at this stage. If the high compression also causes further problems, who is to blame if later something happens ?

I really appreciate your attention and advice. I can report back about the fuel issues. I also found other problems which have to be adressed before the right picture can be taken.

Thanks again,

Peter

Reply to
carl

It would have helped if all that was mentioned before...your situation is far too specific to resolve here.

No one can give you advice on that... because the PROPER answer is:

MAYBE!

In other words.. for peace of mind.. new or rebuilt engine.

"carl" wrote in news:9w6Ee.150887$ snipped-for-privacy@phobos.telenet-ops.be:

Reply to
Backyard Mechanic

"Backyard Mechanic" schreef in bericht news:Xns969B71D03E56Epettyfogery@207.115.63.158...

Hello,

I thought my post was long enough for a first message :-). And I was puzzled what to adress first. So I will really look into the filter problem, also suggested by a mechanic I saw last week.

It is a pity that people assume nothing can go wrong, and let customers worry about overheating. Venting the system on a cold engine is IMHO a far better way to avoid problems than letting it idle. And no mechanic found 17 bars compression something strange yet except for one - and you :-)

My problem is a set of issues, and I begin to see more clearly now. Thanks again.

Peter

Reply to
Peter

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