Heat from engine

[sbbro]

I have another question for the board... on my recent purchase of an 88 535is Ive been noticing quite a bit of heat coming into the cabin while Im driving. Mostly it starts on the freeway after a couple minutes. The Thermastat reads normal, but It feels like the heater is on. There is no longer insulation on the hood, dont know if they ever did come with like the m5's, but could this be the cause?? has anyone else experienced this?

[Patrick McHugh]

The e28 uses an electro magnetic solenoid to control the amount of coolant entering the heater core.

If it fails it usually fails in the open position.

I'd start by checking the heater solenoid, it's located on the firewall near the brake fluid canister. It's normally open, if you have someone turn the knob to cool, you should get voltage at the connector and or feel it close.

A bunch of people are going to tell you to use the search function. Just a heads up.

[Shawn D.]

Two words to search on: "firewall plug"

[Mike W.]

It could well be the heater valve and tired seals in the heater box, I've had that myself. But your comment about no hood insulation points towards another possibility, if the seals are gone around where the fresh air passes from the hood vent thru the firewall, that too could be your problem.

[h2dave]

i have the same problem and i think it has to do with air rushing through the hood vents into the car,i notice mine comming through the defrost vents mostly.i have a new heater valve and i checked the operation of it and it works fine.make sure all your knobs are slid over towards the drivers side.
dave

[BRRV]

You didn't say where this heat is coming from. It's a process of elimination, with some fixes easier than others. BTW - this is a very common problem with european cars from this era - they ALL do it in one form or another. Personally, I don't think this has to do with the lack of any insulation on your hood. Assuming that this heat is coming from the area around the accelerator pedal - first thing is the heater valve, as mentioned - replace the guts and see if it goes away. Next are openings in the firewall (BMW calls this the splashwall, I think) specifically holes around the pedal brackets and so on. If you are getting warmer than ambient air through the center vents, then the seals on the intake vents on the hood aren't sealing the engine bay from the ventilation system. These three things should eliminate MOST of the heat coming into this area. The last fix is the most difficult and it has to do with the flaps in the heater box/ventilation system itself. If the foam has disintegrated, they won't seal, and you can get ambient air leakage through them, even with the sliders all the way closed (this is more noticeable as cold air leaking through the center vents in the wintertime when you are running your heater, though). Lastly, you can get a lot of really warm air from the transmission shift area on the driveshaft tunnel, due to inadequate or missing rubber or insulation. This is very very common - many mechanics don't properly reinstall/replace these materials back on the car after a repair, thinking that somehow they are superfluous (ask me how I know this). I've seen it so bad that you can remove the shifter boot and see pavement - and the rush of really hot air will make the car unbearable. Try these items and, if it doesn't improve, get back to us with more info.