ELJG

My 95 928GTS is running just fine except some 20 minutes after shutting down the engine the inside of the cabin is completely steamed and that's with nobody in it! I am not losing coolant and cannot see where the steam is coming from. Moisture is now in the area, behind the glass, where the gauges are. Any thoughts, suggestions would be much appreciated. (The aircon was fully refurbished a couple of years ago and it works fine - cooling and heating).

All the best,

76FJ55

Well something is causing high humidity in th e interior of your car. the first thing that comes to mind is a leaking heater core. but as you are not loosing any coolant this may not be the case, or the leak could be slow enough that you haven't realized the lose of coolant yet. also the AC system should have drains that allow condensate to drain off the bottom of the evaporator coil. if these drains are clogged the moisture will stay in the car, or you could have a leak or other source of moisture getting into the cabin. have you pulled the floor mats to check if the floor is wet underneath them? if you have water getting into the cabin and run the heater you will raise the amount of moisture tha air can cary (higher temp air = greater moisture carying capability) then when the car is turned off and the air cools you will reach the dew point and the excess moisture will condense out on cooler objects.

dprantl

Heater cores can leak very little and cause exactly what you describe. Another thing to check is the recirc flap box. Make sure there is no wetness in the passenger footwell and check the fuse/relay panel for moisture.

Dan
'91 928GT S/C 475hp/460lb.ft

Calgary Ole

I agree that the heater core or fittings to the heater core are leaking ( I had this problem with a car some years ago ) Makes sense that it fogs a short while after shut down as the heater valve will open when the vacuum decreases. When I had this problem, I could smell coolant inside the car.

ELJG

Thanks guys, will check it out at the weekend. If heater core, how major a job is this? Thanks.

(no wetness in passenger or driver footwell, but will check again tomorrow)

Lizard928

I would recommend a different approach to this.

Take the car out for a good 2-3 hour drive. Put the heater to full hot and turn on the air conditioning and crack open one or both windows. Do this far a few days in a row.

When my car sits for a bit and we get a lot of rain I get this problem too. This cures it every time.

pcar928fan

90% chance of heater core leak... If the car is not driven much in the rain and does not sit outside I would discount the possibility of a leak in to the cabin...

gitane

Remember that the AC comes on even in heat modes, especially defrost. If the condensate drains are blocked there's a nice little puddle for vaporization. Check that the drains are clear.

danglerb

Heater core is a big enough job you will want to consider replacing the evaporator coil while your in there, its buried in the dash.

ELJG

My poor car is out in all weathers (the garage is not wide enough for it) and it has been raining a lot lately.
Will try the 2-3 hour drive with the a/c on maximum heat but it will probably still be in the rain. The drive today was about 2 hours - full blast heat outwards and freezing cold (all a/c) inwards - net result as described.

WallyP

Pull the carpets in the rear seat footwells and check for wetness. If they are wet, check at the top of the hatch and around the quarter windows for signs of leakage.

Check in the hatch area and the front floor areas as well.

ELJG

Thanks, will check it out tomorrow - it's 21:39 London time.

pcar928fan

Yea, if the car is out all the time and driven in the rain a lot it may well be a leak and water IN the car vs. the heater core. My heater core leak works like this... Turn the heat on (at anytime) and the windshield will fog up for just a few seconds and then clear... that is it. Oh, you do SMELL burning coolant from time to time when you get out of the car or if the windows are down as the drain for the evaporator coil dumps out just above or very near the exhaust pipe.

Good luck...starting to think leak now though...That might be easier to fix with a couple of seals vs. taking the whole damn dash out to fix a leak in the heater core!

Sailmed

If your girlfriends name is "nobody" - Maybe you need to "just get a room" as my kids would say.

ELJG

Now fully checked - no moisture in the hatch or footwells. Still to check the fusebox. Symptoms as described by pcar928fan - just had not paid attention to the few seconds misting at start up... Guess that rules out the seals. Could it still be the recirc flap.. or condensate drains or is the heater core the only possibility left? If so is there a fix or just replacement?
many thanks and all the best