Re: erratic idle on start up

I do hope you are both wrong about the head gasket as i really cant be assed with the hassle of changing that on this engine.

There are two things that also made me think that this may be the case, the first was a tiny bit of white sludge in the iol filler cap, but i wiped this away around 3 weeks ago and it hasent come back.

the second was a tiny bit of brown scum on top of the coolant in the header tank (the scum just looks like ordinary discoloration of the plastic that you get). I did not clean this scum out, this was about

If it was the head gasket, surely this would happen every time the car was started and not just when it had been left to stand for long periods? Also the problem is speradic, if it was the gasket, it wouldn't be would it?

I think i am trying to convince my self its not.

Thanks for the advice, keep it comming.

i still think its the gasget. ok try this. put the heater on full hot and take the cap off the coolant bottle. top up the coolant too maximum and run the engine untill the rad fan cuts in with the cap off. now its nice and hot watch and see if there are any bubbles. lots of bubbles = headgasget failer.

not true, on this engine only the very worst headgasget failer would do that, most however will run for years with a slight headgasget leak if you bleed the cooling system reguarly.

Cheers for the advice, i still hope your wrong about this one.

I will try the heater thing, i have never heard of doing this before. Hope fully i will be posting back with no bubbles.

Could it not just an ECU fault?

The more i think about it (now dont laugh) i think it could be a very small fuel leak, leading to a drop in pressure when the car has been sat for a while. This would make it idle funny until the pump brought the fuel back up to pressure, wouldnt it?

Cheers

Right, at the risk of sounding really stupid i have tred your test and think I (not the car) failed.

1. I put the heaters on full blast on hot
2. I took the header tank cap off and made sure the coolant was at max
3. I sat the car at 6k rpm until it reached 70'c

(well i had my mrs do that while i watched, the only prodlem was i couldnt here the fan above the engine noise)

1. I told her to stop reving the engine at 70'c
2. I heard the fan already at full tilt
3. I watched as the water swelled out of the header tand and all over the engine.

Now i thought that no matter what i did with the heater, water would come out of the tank if the cap wasnt on.

The header tank (im sure you are familier) is in two halves, the return on one side and the fill on the other.

From the word go the return had what i would call bubbles in it, from the force of the water being returned to it into such a small space.

The fill never had any bubbles in it until all the water came out, which i think was all from the return anyway.

So, as i am clearly very lame, can you please post detailed instructions on how to do this test?

Should i have left the car on idle to reach temp?

should i have stopped reving at lower temp?

Should the water stay in the tank no matter what is wrong with the car?

One final thing, if it is the gasket, wouldnt the coolant temp be high all the time? The temp sits at a very low 70'c all the time, the fan very rarely kicks in at all, except if you have been moterway driving and suddenly come to a stand still and even then it only comes on for a few secs before going off.

Thanks again. (sorry to be a pain)