Author Topic: Coolant boiling, bleeder hole leaking (Read 8725 times)

PumpItUp · « **on:** June 01, 2010, 02:05:35 AM »

So a day after I made fun of people converting to E36 radiators karma strikes!

Once reaching operating temperature, coolant begins to boil. Eventually leaks out the bleeding screw. Temperature gauge at the middle & doesn't indicate over heating, though a bit higher than it used to be. Slowly climbs at idle. It's boiling prematurely (i.e. from a leak). Even if it's been warm recently, all I did was highway driving, literally all my driving. Pull off the road, pop hood, already boiling.. so it's not the fan, which is the oem clutch+shroud btw since i took off the electric conversion to clean up its appearance as when I originally fit it I cut the plastic using gardening tools.

-System is bled
-Heater works
-Oil looks brand new
-Coolant doesn't have oil
-Water pump & thermostat was replaced a month or two back.

At the very least the water pump is not the problem.. :rolleyes:

I'll buy a new radiator cap tomorrow and am making an online order of several things. But in the mean time.. any ideas? Lay the bad possibilities on me!

PumpItUp · « **Reply #1 on:** June 02, 2010, 01:37:07 AM »

So it seems to be just a bleeder hole leak, not a more serious problem causing this. The screw is fine, it's a small piece of the radiator that's cracked. I'll seal it for now

gotta love those plastic behr's, really feels like a 90s car alright.

PumpItUp · « **Reply #2 on:** June 02, 2010, 02:01:24 AM »

I know this is a common problem but HOW's IT GONNA BREAK when I didn't even touch it. I didn't over tighten the screw after bleeding it. What a POS

Choking Hazard · « **Reply #3 on:** June 02, 2010, 08:13:59 AM »

Just to be sure, I would look at the no. 2 spark plug and be sure it is dry...

My radiator separated where the top hose attaches. My brother had borrowed thge car. He pulled into the driveway at 5:30 am so we could go to the airport and BOOM- Blue stuff blew right out of the grill and from around the left headlight (lights were on) like some kind of sci-fi movie.

It actually turned out to be a symptom- tiny crack in head (at cyl no 2) caused low coolant resulting in boiling- then high pressure blew up the old plastic hose connector.

DesktopDave · « **Reply #4 on:** June 02, 2010, 08:46:23 AM »

I agree...a cooling system can only boil if it's at low pressure from a leak (or too much air in the system), or if it's being pressurized by a leaking cylinder. Some mechanics can check for exhaust in the coolant, that's where I'd start just for peace of mind. Especially since the car is staying near the middle of the temp range.

BTW, these are the classic symptoms of a profile gasket leak. I'm sure your car has the updated gasket...but a gas leak from the head would definitely cause symptoms like this.

PumpItUp · « **Reply #5 on:** June 03, 2010, 04:27:14 PM »

I checked the first 2 spark plugs yesterday, they were fine, just kind of white, but I think that's from seafoam a while back. Got lazy on the other two since I'll do a compression test today. Thanks for the response

ten2doyle102 · « **Reply #6 on:** March 29, 2011, 09:07:38 PM »

Sorry to bring this back from the dead..... But I am dealing with exactly the same issue on my new 318is. I was wondering if the problem was ever figured out? I was hoping that it was not the profile gasket in this motor. It was said to be rebuilt so I can only hope that it was rebuilt with quality stuff. I can't seem to get the car to bleed properly at all either. When its been running for about 30 mins... I can grab the upper hose and squeeze it only getting what looks like steam from the bleeder. The lower radiator hose is cold.

I pulled the waterpump and thermostat out today and found that the little arrow was pointing downward. To me, i would think you'd want that up. Also, I found that there was no little hole to allow coolant through and read somewhere about people drilling a small hole into thermostats like this. Is this possibly part of problem?

I haven't pulled the plugs either to see what they look like. Not exhaust in the coolant either.

I have a new water pump and thermostat coming for tomorrow so I am only hoping that this might help... lol.

DesktopDave · « **Reply #7 on:** March 30, 2011, 06:06:08 AM »

Might be a leak somewhere. I'd try to pressure test the system. When the coolant heats up, it expands. If the system isn't pressure-tight to at least 15psi, the coolant boils and the car overheats.

The thermostat orientation doesn't seem to matter in our cars (though I prefer the arrow pointing up myself). The (absent) hole in the thermo flange is to prevent bubbles from collecting at the thermostat and causing an air-lock, seems BMW decided against it. I'm guessing that no "weep hole" permits the motor to warm up a bit faster & helps with emissions a bit at the expense of bleeding it easily.

Last time I worked on the system, I filled both the radiator hoses first, before tightening them up at the thermostat housing. Helped a lot with the bleeding.

ten2doyle102 · « **Reply #8 on:** March 30, 2011, 06:33:05 AM »

Sounds good. I was planning on filling up both hoses first like you stated. I hope I can get this figured out.

http://m42club.com/forums/showthread.php?t=9603&page=6

I read through this whole thing last night....

Seems like it was never really truely figured out what the cause is. If it was a profile gasket, are there any tell tale signs that I should be able to see on the outside of the motor? I was getting small drops of coolant randomly, but it looked like the thermostat was leaking... Also, I read about people suggesting to use a liquid sealer along with the paper gasket.... is this a good idea?

ten2doyle102 · « **Reply #9 on:** March 30, 2011, 06:35:42 AM »

Also, is the coolant sensor on the m42 radiator the same as a sensor from an m20 radiator?

DesktopDave · « **Reply #10 on:** March 30, 2011, 09:06:59 AM »

I've seen a lot of people put silicone gasket compound on the profile gasket to seal it. You've likely seen that too...it's the orange/gray/red/black goop, comes in what looks like a toothpaste tube. And it's not a paper gasket at all...it's a thick rubber one. I'd use a brand new one instead of the silicone, but either method should work. Be sure that gasket gets "pre-loaded" when you install it. The profile gasket is thick, needs to be squished a bit to fit properly. Also check to be sure the head isn't eaten away by coolant...if so, you'll have to resurface it with something tough like metal filled epoxy.

The coolant temp sensor on the radiator is actually the aux fan switch, sometimes called a "fanstat"...it's not a sensor (those are both on the motor, in the head cooling jacket). The fanstat is the same size physically on a few BMW motors. I've swapped the M42 one with M20 switches in the past to test the aux fan system. They do differ in their high/low temp settings though, and (I'd assume) should match the thermostat temp pretty closely. The stock M42 thermostat fully opens at 88degC IIRC. The matching M42 fanstat switches on low at 80degC and high at 88degC.

I'm putting a 92degC thermo & 92/99degC fanstat in mine later this year, hopefully to eke out a bit more fuel mileage.

ten2doyle102 · « **Reply #11 on:** March 30, 2011, 10:28:38 AM »

The paper gasket i was referring to was the thermostat gasket. I know the profile gasket is a thick rubber seal. Is there anyway to test to see if its bad? I don't see and coolant residue around the gasket at all....

DesktopDave · « **Reply #12 on:** March 30, 2011, 10:47:46 AM »

The only easy way to get a good test on the cooling system is with a pressure pump & gauge. If that profile gasket is leaking internally I can't think of any way to easily determine that...other than maybe oil contamination? Your guess will be better than mine...

Coolant leaks are usually hard to tackle, as they just evaporate or wash off. The oil all over my block waterproofs it anyway...

Leaks are pretty common on the plastic water pipes & the rat's nest of pre-heater hoses. They're hard to track down due to the intake manifold & wiring conduit being in the way. E30 heater cores are pretty frequently leaking too (though that's easy to smell). The heater core tends to leak out of the HVAC drain or under the carpets.

ten2doyle102 · « **Reply #13 on:** March 30, 2011, 10:20:18 PM »

I am not seeing any leaks from anything anywhere. Its weird. I replaced the thermostat and water pump today and bled it for a while. It seems to be better now, but its hard to say. I am also going to be replacing my cluster with a known good one. The odo stopped working and the temp gauge moves alot if I tapped on the front of it. Also, whats a good way to measure the temp manually? My friend has a laser thermometer to use.... is there anything that I can check it on?

DesktopDave · « **Reply #14 on:** March 31, 2011, 03:58:14 PM »

I'd check the thermostat housing. It'll heat up rapidly with the coolant flowing through it once the thermostat is open. Aluminum also doesn't insulate very well like the rubber hose or nylon end tanks.