Why cant things be easy! Overheating issues

Post Tue May 10, 2005 9:30 am

BMW E30 325i F reg

Right a few days ago the coolant light came on so I topped it up, only appeared to be down a smidge. Been fine was driving all over the place.

On the way into work today I was just pulling out of a petrol station and the noticed the temp gauge was up showing surface of the sun temp!

Stopped immediately and found a small trickle of water from the expansion tank where it had boiled over. Checked all the hoses and they were all hot even the heater ones. Waited a bit and gently released the cap to find a lovely boiling water. No sign of oil in the water and no sign of water in the oil. So not head gasket or head I hope.

My theory at the moment is an air lock any ideas on how to check, I hear of a bleed screw but have no idea where it is?

Post Tue May 10, 2005 10:02 am

ok, ive recently had this problem but it could be a no. of things.
1 a blockage somewhere.
2 thermostat locked open or closed
3 pump
4 head gasket

i first thought it was the thermostat in mine so i changed this. this is situated under a cap where all the big hoses meet in the front center of the engine bay. standing on the passanger side there will be three 10mm bolts. its in there, may be worth replacing, costs under a tenner.
the bleed screw is the one directly on top of this housing, you cant miss it.
however mine turned out to be the actual housing so i had to replace the lot. theres a smallish pipe underneath this which had got blocked up and eventually blew off taking the connection part with it

im sure theres a way of testing the pump but im not sure how.
head gasket? lets hope not.

maybe some else can shed some more light

regards

Post Tue May 10, 2005 1:27 pm

have just done my coolant on the 320...(m20)

what to do is this...

when car is COLD and not been run for a while

1.spray the 8mm bleed screw with plenty of WD40

2.take off bottom radiator hose, and let coolant drain

3.locate the thermostat housing (at front of engine next to distributor cap)

undo the 3 bolts holding it together (10mm iirc) and remove the thermostat. (may require removal of the fuel line next to it, so disconnect battery to drop the fuel presure)

4.bolt the housing back together and put a hose in the expansion tank, let the water run through until its clear.

5.take the top hose off the radiator and run water through the radiator until its clear.

6.reattach all hoses and reinstall the thermostat.

7.mix up coolant about 40/60 coolant/water and pour SLOWLY into the expansion tank, giving time for it to 'gurgle' down.

8.system should hold about 4.5l of coolant

9.once full (to cold coolant level) put on expansion tank cap

10.reconnect battery and set heater controls to FULL (HOT and fan speed 4)

11.start car and let it idle for about 10mins, to get up to temperature.Keep an eye on the pipes and make sure they dont get too solid (too much air in system)

12.then SLOWLY open the Bleed Nipple, and let the air (and some water) escape. Do this in several short bursts over maybe a 5 min period.

13.Repeat the above procedure until all the air has escaped.

14.sit back and admire your temperature gauge sitting at the 1/2 way point

1hr should see this done if you're careful

Post Tue May 10, 2005 6:51 pm

Right well I've also found a bad oil leak on the front drivers side of the engine that seems to have a constant drip when the engine is running (about two drips a second).

I'm gonna change the thermostat in the morning I think it's just sticking as it was alright on the way home. When I refilled the water levels it took about 2.2 litres before it was normal it seemed alot for just boiling up a little.

Post Tue May 10, 2005 6:54 pm

depends how much air is in it!!!

my 525i took nearly 4l to fill after diagnosing air i the system...

bleed it like I say with a new thermostat and then take it from there-its a lot cheaper than a new head....

Good luck!!

Post Tue May 10, 2005 8:31 pm

A head gasket can be gone with no signs of water in oil or vice versa.

If the gasket fails between a cylinder and a waterway you will have a blown head gasket, there will be no water in the oil etc etc as you haven't blown a gasket between the waterway and oilway.

Head gaskets have to be really fcuked for it to get oily water etc and overheat.

Usually, driving a car that overheats due to compression getting into the coolign system and pumping the coolant out at 175psi will lead to a mayo oil gasket failure.

Catch it nice and early and do it properly and you might not be saving up cash for a new head.

Post Tue May 10, 2005 8:52 pm

andy I have no mayo at all there was a touch of water in the exhaust but no white clouds or anything

The oil leak is a bit more conserning what is the sensor below the manifold on the drivers side that seems to be where the oil is dripping from?

Post Tue May 10, 2005 10:09 pm

The oil leak sounds like the pressure switch is leaking, you might fix it by tightening it up, although I think these can fail with age leading to a leak.

The best way to check woul dbe to clean the area up and then run the engine and watch where the oil actually comes from.

If it comes from between the block and the sensor you can probably tighten it a little to cure it, if the oil is coming out of the switch you'll have to hit the dealer/scrappy depending on your budget