Coolant dropping - no leak - misfiring

edanto

My sister's Polo is being a bit wierd - strange whining sound, chugging when starting, won't start on a hill and coolant level dropping quickly even though there is no sign of a leak. The dashboard is lit up like a (small) christmas tree with the exhaust emissions light and the coolant level light.

The temperature guage is always in the normal range & one mechanic that checked it plugged it into the computer and got an error that said 'P0300 Random sporadic multiple cylinder misfire detected' This insipred him to change the coil and the leads, but after that repair the car behaves the same way and the computer gave the same readout.

A search on the VW forums mentions the head gasket as a fix for coolant problems - but they always seem to have the symptom of overheating too and this one isn't (obviously the guage could be broken!). The next step is to take it to a VW dealer when she has the readies next month, but in the meantime are there any suggestions/questions, pls?

Webmonkey

Thinking head gasket myself. Mightn't always over heat, head gasket's can go slowly. Water could be getting in cylinders causing misfires.
No oil in the water by any chance? or mayo style stuff on the oil dip stick? - If so sure sign of HG.

IrishRover

If it wasn't for temp levels being normal you'd say no question headgasket.
Check for other signs of HG failure such as mayonnaise (coagulant) on the dipstick and in the coolant expansion tank and under the oil filler cap.

Also check the rubber coolant pipes for extreme firmness when you try to squeeze them even after shutting engine off after driving as this would indicate the coolant system being pressurised by not having a proper seal between coolant system and combustion gases.

Warning: be careful when opening cap on expansion tank. Leave it a few minutes after shutting off engine and allow to cool down a bit before opening. Hot coolant under pressure can spray out and burn you.

bushy...

If the level is dropping , there aren't many other places the coolant can go if its not leaking . It can go into the oil as Webmonkey said , or it can get sucked in through a head gasket / cracked head / cracked cylinder or maybe if it has it a dodgy coolant heated manifold .

junkyard

Get a mechanic to do a hydrocarbon test on it, you'll get a quick result from it one way or the other. I'd be 99% sure its a headgasket problem too by the way. Also check if the interior radiator is leaking, a smell of coolant or damp in the car and a damp carpet, its no unheard of with VW's among other things.

edanto

Check for other signs of HG failure such as mayonnaise (coagulant) on the dipstick and in the coolant expansion tank and under the oil filler cap

I didn't think that there was any of this, we just went out and checked it again - the oil is pure oil and there isn't any kind of oily stuff on top of the coolant in the expansion tank.

mechanic to do a hydrocarbon test on it, you'll get a quick result from it one way or the other

Would you mind filling me in on what the results of this test would mean, please?

Also check the rubber coolant pipes for extreme firmness when you try to squeeze them even after shutting engine off after driving

No, they're not that firm, car was recently driven, has been sitting for a few minutes and the big rubber tubes aren't ridiculously firm or anything. There is a pressure problem with the coolant though - when you open the cap on the expansion tank, there's a rush of air (probably in) and if you don't let it equalise before opening it the whole way, then a load of coolant pours/erupts out.

and thanks for the help so far, all!

Webmonkey

The pressure thing you described there is not a problem. It is a good sign of the cooling system. Shows that it is pressurised which it is ment to be.

mike65

Thats cos the system is pressurised and the coolant is hot (I presume!).

edit beaten to it!

Mike.

Doodee

Low coolant and power sterring pump?


I had similar problems with mine and was told by some that it was either the head gasket or the clamshaft but it turned out to be just leaking coolant and the power steering pump gone.

junkyard

edanto wrote:

Would you mind filling me in on what the results of this test would mean, please?

If the results are positive i.e. hydrocarbons mixing with the water, means the headgasket seal is leaking and the emissions are leaking into the coolant and pressurising the system and causing the engine to overheat.

IrishRover

I should have said over-pressurised. Yeah it's under pressure normally, but an indication that it is over pressurised is when you cannot compress the rubber pipes at all, even a long time after engine switch off, or if there is still a release of pressure from the coolant cap even hours after switch off and the engine has cooled down.

The hydrocarbon test will show if there's exhaust gases in the coolant, and if so it means that there is no longer a seal between a cylinder and a coolant passage.

Then again you say you already have an emissions warning light and a cylinder misfiring so that ties in completely.

HGs can "fail" in different ways, you could say there is "damage" to the HG between a cylinder and a waterway, but it hasn't "failed" yet as such.

Webmonkey

Doodee wrote:

Low coolant and power sterring pump?


I had similar problems with mine and was told by some that it was either the head gasket or the clamshaft but it turned out to be just leaking coolant and the power steering pump gone.

Correct me if I'm wrong but i can't see what the cooling system has to do with the power steering pump?

Doodee

Webmonkey wrote:

Correct me if I'm wrong but i can't see what the cooling system has to do with the power steering pump?

I was just sharing my own experience on it.
Never said it was the problem, just that I had a similar issue.

is there a problem with this?

Webmonkey

Not at all Just curious

edanto

Well, doodee, thanks anyways. Did you have a really obvious leak from your coolant system? As in a puddle under the car?

I'm gonna look into getting a hydrocarbon test - the results of that could be really valuable. My sis would like to try another mechanic, she's not impressed with his level of service or know-how. Can anyone recommend one - north dublin city?

Esel

Doodee wrote:

...was told by some that it was either the head gasket or the clamshaft....

Doodee, only you could have problems with your 'clamshaft'!

junkyard

esel wrote:

Doodee, only you could have problems with your 'clamshaft'!

Hey!! enough of this off-topicness or ye'll have JohnCleary to answer to.:D

mike65

Not too far from a googlewhack

Mike.