coolant loss

[Squiggy]

Hi,
Last year I had my head gasket (& radiator, thermostat and water pump) replaced. Since then I lose about 1/2 pint of coolant per week (@ 100 miles per week).
There is no obvious leak, the heating works fine, there is no obvious steam from exhaust, no mayonaise anywhere, and the garage say that a pressure test is OK.
What the hell is going on? How can I diagnose this problem?

Squiggy.

 

[Softus]

There is no obvious leak, the heating works fine, there is no obvious steam from exhaust...

How visible would you expect the water vapour to be, given that the rate of loss is only 6cc per mile? Or, to put it another way, a teaspoon per minute?

...the garage say that a pressure test is OK.

What was the test that they did?

 

[Stivino]

They probably connected a pressure tester to the system (usually the water bottle) pump the pressure up using the pump provided. See the link.

http://cgi.ebay.com/ebaymotors/UNIV...categoryZ43989QQcmdZViewItem#ebayphotohosting

Are you sure it's not just finding it's proper level? You top it up with a pint too much and it's spitting it out again.

 

[^neo^]

What car is it?

 

[Squiggy]

Softus, you make a good point, but I still need to diagnose the problem.
I presume, though I don't know for certain, that they tested with the method Stivino suggested, I need to ask. I presumed they knew what they were doing, but cold or hot engine test, again I don't know.

If it is finding it's right level, the level is bloody low and dramatically lower than before all the work was done!

Can you hire these testers? Or make one?

 

[Squiggy]

Sorry, forgot to add it's a 1989 BMW 520i, auto gearbox.

 

[Softus]

I'm not clear why you waited between 4 and 16 months before deciding to do something about it. Unless you don't trust the mechanic(s) who did the work last year, then I would take the car back to them for diagnosis.

 

[Squiggy]

It has been back, they say they cannot find a problem, therefore I do not trust them. QED.

 

[jayzee]

your problem sounds as though you are losing a small amount of pressure in cooling system giving rise to coolant loss.I have often found the rad cap to be the culprit,which may not have been tested.Pressure testing may not show a loss if the problem is minute,but for starters try a new cap,if problem persists try undoing rad cap after a run (carefully)do you get a hiss to indicate pressure is being held.If hardly any hiss-pressure has been lost.

 

[Softus]

It has been back, they say they cannot find a problem, therefore I do not trust them. QED.

Are they not human? Are they not capable of error? Do they not deserve another opportunity to remedy the problem that might have been of their own making?

Tell you what - you're not very trusting, therefore you're not very trustworthy. QED.

 

[Squiggy]

Softus, chill man, I only asked a question, that's what this forum is for. Shame you cannot contribute in a sensible way, instead of constantly giving useless opinions.

 

[Softus]

Leaving aside your poor attempt at sarcasm, you have a short memory...

Softus, you make a good point, but I still need to diagnose the problem.

Shame you cannot contribute in a sensible way, instead of constantly giving useless opinions.

In what way is my opinion that you made a rash judgment [about your mechanic] any less valid than your opinion about your mechanic? Or is it just that I observed about you something that you'd rather not accept?

 

[Squiggy]

Is your psychoanalysis based upon Freudian techniques, or based solely on the works of Onan?

 

[Softus]

Is your psychoanalysis based upon Freudian techniques, or based solely on the works of Onan?

Perhaps you think that an attempted insult is an adequate distraction from the fact that you can't answer a straightforward question.

It isn't.

 

[^neo^]

Park it somewhere dry and lay some newspaper under it. Run it til it's hot, turn it off and leave it a couple of hours. If there a no wet patches or signs of leaks then you're obviously losing water inside the engine (headgasket / head / block)