Steamy GM900 2.5

[steventon95]

This standby car (2.5 GM900 Coupe) tends to get very misty within, and I suspect a very slight leakage somewhere in the cooling / heating plumbing. The water loss is very slight and only needs a top up after a couple of hundred miles. Nothing at all obvious on opening the bonnet, even after a longish run. Any suggestions as to the most likely place to look for a leak?

[phoenix]

Sounds like it may be more due to blocked air con drains, especially if you're not losing a lot of coolant and there's no smell. I'm not familiar with where they are on the GM900- perhaps someone else is?

[steventon95]

Somebody has also suggested heater matrix leaking, which sounds quite possible. That would be mildly irritating as it could cost a bit.

[phoenix]

A leaky heater matrix is normally accompanied by a distinctive sweet/sour smell of warm coolant. One way to check is to push the front seats fully forwards and see if there's any evidence in the under seat air ducts that heat the rear.

I've had a look at the parts diagram and it would appear that the a/c drain is the flexi tube about 2" across that sits in the middle of the bulkhead in the engine compartment. Check it isn't blocked.

[steventon95]

I shall go and peer into the innermost recesses when it gets a bit less cold.  Just driven 140 miles without undue steaminess. Maybe it was all due to carrying wet sheep in the back ... or something.