Coolant system trouble

[PeteK]

Trying to track down the reason why my coolant is disappearing. Can't find any leaks, so I'm guessing it's overflowing when hot.

Anyway, my query is that, after topping the coolant up and running the car up to temp (with the cap off), there was a whole lot of foam coming out of the open cap. Anyone know if this is a problem or is it just air releasing from the system?

[Peter V.]

If it is a lott of foam in combination with bubbles then probably your headgasket is finished.

[Jeroen]

Looks like it, yes. First quick check: with cold engine, remove spark lugs, leave them in order, check for differences in color.

[PeteK]

Pulled the plugs and got myself a compression tester. All cylinders showed between 120 and 130 psi. This sounds too low for 9.5:1, but since they're all the same, I'm guessing there's no failed head gasket. No water in the oil and no water leaking out.



Feeling better, but still loads to do.

[Jeroen]

And the colors on the plugs? BTW what made you think the head gasket may be blown in the first place?

[PeteK]

The plugs were all uniformly dark and pretty sooty. Not pretty, but ok.

I've got air bubbles coming out the overflow and coolant is disappearing without any obvious leak. She is also running really badly.

Just got to get to mechanic tomorrow and hopefully they'll list out all the repairs. Lucky it's too hot over here to drive without an air con anyway!

[uwbuurman]

Foam at the mouth? Rabies?

[Reck]

Hmm, that is an odd one. I believe when I was losing coolant - the first issue was an exhaust gas leak into the coolant (which was then creating air/gas pockets, pushing coolant from the overflow pipe and meant I could never bleed the coolant properly and had to keep topping up). Second, a bad solder/braze on the neck of the rad (would only leak at operating temp/pressure, and even then it was difficult to see..).

Watching with interest, fingers crossed it's nothing serious! Keep us updated.

[Eddie.]

My system also foamed badly when bleeding it recently, and my heaters don't work.

Would you guys be checking the headgasket first then?

[PeteK]

The head gasket check was just because I could (and I wanted to anyway).

Here's the results. I'm assuming that the results are a bit low, but similarly low is OK. Test was run dry with fuel pump fuse pulled.