overheating when not moving?

[spike318is]

hi, i've got a 1990 e30 running a m42, after a harsh winter here in ireland my e30 seems to have developed a problem with the cooling system. i always let my car get up to temperature before starting any journey. recently i have noticed that hot air does not come from the interior vents until i have driven a few hundred yards, also if the car is not moving it will start to climb the temperature gauge and over heat. any ideas on what may be going on? personnally i think it may be either the viscous fan, water pump or possibly even the thermostat. also during the -18 temps here my car got a proper chill, there was anti freeze in it but the collant did partially feeeze, did not freeze fully was just like a thick slush. any help will be appreciated.

[DesktopDave]

I never warm the car before any drive.  I just give her a few seconds to get the oil around, then off we go.  I'd advise against idling for extended periods.

I'd guess you just have too much air in the system.  Might be a bubble, leaking radiator, expansion tank seal, pressure cap, etc.  You can test the engine fan with say ten pages of a newspaper.  Turn the motor on...roll the newspaper up & stick one end in the fan.  When the fan clutch is cold, it'll have trouble with the paper.  When the clutch is warm (locking the fan up), it'll shred it.  I wish I had a more scientific test, but that'll do for a quick result.

If you don't see any obvious leaks, I'd drain the coolant (both radiator and block drains) & do a pressure test.  That will tell you a lot about the condition of the system.  15psi/1bar is all you need.

Frozen coolant isn't a good thing either, even a slush.  I wouldn't think it did damage, but water does expand as it freezes, hopefully it only stretched the hoses a bit.

[spike318is]

that would make sense, to try and limit damage durnig the cold weather i removed but top and bottom hoses from the radiator and engine and removed all coolant that i could and removed as much as i could from the head. what is the best way to bleed the collant system?

[DesktopDave]

You shouldn't have to remove any coolant during the winter.  A 50/50 BMW mix is good down to something like -35degC ambient temp.  Not sure why it slushed on you...odd, that.  If you're worried about freezing, you can take it up to 70/30 antifreeze/water for protection down to something crazy like -65C.  Always use distilled water too.

I bleed the system with a garden hose.  Pull the main hoses & flush the radiator & expansion tank.  Also be sure you drain the block - remove the block drain bolt under the exhaust header.  Pull the heater hoses, turn the heater control to full hot & flush that with the hose until the water runs clear.

To refill, I usually park the car facing up a hill.  Then I pull the low side hose and fill that first, re-attach.  Then I fill the expansion tank & loosen the bleed screw about four turns.

I start the car, keep squeezing the upper hose to see if it's filling up yet.  Once I can feel coolant in the hose and it's getting warm, I tighten the bleed screw a few turns (only until it stops flowing coolant!  Don't overtighten this one, it'll snap right off!) and take it for a spin.  After the car cools off I double-check the "kalt" line on the expansion tank & top off with distilled water as necessary.  I then check it over the next few days to be sure it isn't going lower.

[Voodoo Child]

If you doesn't see any leaks under you're car i would first do what Dave said.
Very bright explanation by the way!  When there is air in the cooling system the temp. needle tends to bounce from my experience..

A couple of days ago my car also went too hot. The difference i have is that when i got home there was  about 1 Ltr. of coolant under my car.
After some research the coollant came from the motorblock itself, where the head meets the timing chain cover.
So in my case it's probably the (in)famous timing case gasket.
Here is a pic. of it ;