Is My Head Gasket Gone?...

[supersub14 1]

I (stupidly!!) left my standard 1.9gti idleing after a hard drive home from work while i went and did summit else and the car overheated

 

I have a switch wired up to the fan (cos fan didnt work when i bought the car) and i forgot to switch it on...doh! It had maybe been sitting 10 or 15 mins before i realised there was steam coming from below the bonnet, but once i saw this i stopped the car immediately.

 

I unscrewed the header tank cap to let the steam out and switched on the fan to try to cool her down. When the steam cleared i filled the radiator up with coolant.

 

Im now concerned that the head gasket is gone as the header tank is slightly pressurising. Are there any other ways of telling if its gone? My brother thinks the car only needs re-bled but i dont wanna drive her and wreck summit else. It got had a new head gasket and the head got skimmed 700miles ago when i changed the radiator and coolant pipes and i dont wanna go through all that hassle again if i can avoid it.

 

Thanks for any help guys!

 

John

[TRYNKEEPUP 0]

whip the cam cover off and see if theres any milky mess in there. doing a compression test may also work, But theres a down side to this if the cylinders got water in it you wont get a correct reading, worth trying though i think.

[Cloverleaf 1]

Do a compression test. Check the exhaust for white smoke when running, monitor the coolant level. Check the oil for water.

 

It's also worth noting that running the fan with the engine stopped will only cool the water in the radiator, not cool the engine. Also, coolant systems are pressurised to increase the boiling point of the coolant.

[Tom Fenton 1,526]

Unfortunately by adding cold coolant to a stinking hot engine you have pretty much done the worst thing you possibly could have done, as the cold water hitting the hot castings causes them to rapidly change temperature, possibly leading to warping.

 

Bleed as thoroughly as you can and then run it up from cold, if it immediately pressurises the coolant system then you most likely have head gasket problems.

[supersub14 1]

thanks, least thats a few things to try!

 

ive never done a compression test before but i did a search on google there and it looks straight forward enough. Any tips?

 

Also what readings should i be getting? I dont have a haynes manual if thats where the values are

[TRYNKEEPUP 0]

im not certain 150 - 155 maybe some one else has an accurate number

[Anthony 1,000]

Also what readings should i be getting? I dont have a haynes manual if thats where the values are

Something in the region of about 170-190psi is about right for a 1.9 8v in my experience, although the actual numbers aren't massively important and what you're more concerned with is differences between cylinders - ideally you shouldn't have more than about 5-10% between cylinders.

 

What I would say is to take the results with a pinch of salt - a good compression test result doesn't always mean that the head gasket is OK in my experience. In addition to a compression check, check for pressurising of the cooling system, the engine running hotter than usual, and the usual giveaway, it using noticeable amounts of coolant.

 

If you're in doubt, then any decent garage should be able to do a dip-test in the expansion tank to confirm any head gasket failure diagnosis.

[supersub14 1]

Ok thats great guys. Least i know what to look out for now. Never had one go before!

 

Tell me this, why would it use a lot of coolant if gasket is gone? Does the coolant leak into the cylinder through the gasket seal then get evaporated? Probably sounds like a stupid question but i dont know much about the actual workings of an engine lol

[richsmells 2]

Ok thats great guys. Least i know what to look out for now. Never had one go before!

 

Tell me this, why would it use a lot of coolant if gasket is gone? Does the coolant leak into the cylinder through the gasket seal then get evaporated? Probably sounds like a stupid question but i dont know much about the actual workings of an engine lol

 

Yep, you've got it. Hence if it's gone in a big way, you get plooms of steam from the exhaust or a nice oil/water/mayonaise mixture in the water and oilways.

Edited January 16, 2009 by richsmells

[SeanO'Connor 0]

Yep, you've got it. Hence if it's gone in a big way, you get plooms of steam from the exhaust or a nice oil/water/mayonaise mixture in the water and oilways.

 

 

or like my mini 1275 gt coolant running out of the exhaust and an awesome misfire!!!!!! Head gasket is less than hour on a mini thankfully though!

[shalmaneser 26]

Ok thats great guys. Least i know what to look out for now. Never had one go before!

 

Tell me this, why would it use a lot of coolant if gasket is gone? Does the coolant leak into the cylinder through the gasket seal then get evaporated? Probably sounds like a stupid question but i dont know much about the actual workings of an engine lol

 

Either that or the coolant gets pressurised by the exhaust gases getting past the gasket into the water jacket around the cylinders, which caused the coolant to push past the expansion bottle cap, and down that run off hose.