Member
I have a 1994 320i with an M50 engine.
Recently the coolant has been boiling (and leaking out of) the expansion tank. Mostly only when the engine is turned off, but I did see it once with the engine on idle.
I'm worried that the coolant is going boil off and the car will overheat when I'm caught in traffic or somewhere I can't pull over.
What could be causing this?
Thermostat and housing was changed a year ago (car was overheating due to stuck thermostat)
Member
You probably lost the head gasket from the overheating and the boiling is exhaust gasses entering the system. Do a pressure test and leak down test to be sure.
Gave away my BMWs, driving a VW and an Audi now.
Member
There's a small chance the expansion tank cap is bad. But most likely you warped the head when you overheated.
Search the e36 subforum for 'overheated' to read up on what to expect.
Attn. NEWBIES: Use the search feature, 98% has already been discussed.
Click the search button, select "search single content type", select the "e36 sub forum" specifically, try the "search titles" then try the "search entire posts".
Member
You are right to worry and not drive the car until you fix it. When the "car was overheating due to stuck thermostat", did it go into the red zone? Does this happen when the engine is cold, or only when it's hot? There are many reasons for overheating besides a bad head or gasket, like radiator/ water pump, slow leak, fan clutch, etc. First quick cheap test for head/gasket is to check for combustion gasses in the radiator. A shop will do this for around $30. Some say it won't detect all leaks, but if it shows a leak, you have a leak. I found mine with a mirror at the exhaust pipe. The car has to be warm and show significant water on the mirror. Eric is right: do some reading.
Member
How old is the water pump?
Doing a compression test would be a good place to start, but if you don't have it right now, you could pull all the spark plugs and look inside to see if any of the piston tops are shinny (steam cleaned). A USB inspection camera would be good to use, they're like $20 on ebay.
Attn. NEWBIES: Use the search feature, 98% has already been discussed.
Click the search button, select "search single content type", select the "e36 sub forum" specifically, try the "search titles" then try the "search entire posts".
Member
This could also be due to a cracked head. Pull the spark plugs out and shine a flashlight down there. If you can see shiny piston, you have a cracked head or a bad head gasket. Also, check if exhaust is pressurizing your cooling system by taking the overflow cap off and starting the car. If it start bubbling or you can hear lots of fluid noise, chances are a cracked head or head gasket fail between the piston and the coolant port. You can get coolant test strips at your auto parts store where you can check your coolant for exhaust particulates. I would also change your oil and see if it looks brown or milky. That means coolant is leaking into your oil.
Member
Yip, the mrs was driving. She doesn't do sensible things like check the temp guage.Originally Posted by zellamay
Will try the mirror on the exhaust. car is going for its MOT soon and an emissions test is part of that
Balogne Cajones
I have one of those wifes too. Wifes cost more than cars.
I dont beleive the mirror on the exhaust trick is a valid diagnostic tool. Many of us get alot of condisation in the exhaust, even on freshly built engines, as water is a byproduct of proper combustion. Unless its a noticable cloud on a non humid day, its debatable at best.
If the temp guage hit red, its most likely toasted. If not, bleed the system best you can. Keeps pissing coolant?, get new tank cap. Tank cap doesnt fix it, read the head gasket diys. You will need a new head undoubtedly. Best to getentire upper engine gasket sets and dr. Vanos sets as well.
Nobody would recertify these machines after somebody screwed with them without any visibility into what they did.
HONK! HONK! Clown car coming through!
-Oakdizzle
Driver
Too much panic, don't assume the worst (yet).
If coolant is boiling you have a pressure leak - coolant can't boil under pressure unless it's like at 1 million degrees (perhaps slightly less).
But you say your expansion tank is leaking? That could easily explain your symptoms. Fix that first and then get a coolant pressure test to make sure the system holds pressure. If it does you're probably good to go.
Check your oil cap for white milky emulsion to be safe.
'96 M3, S50B32, 6MT
+ good stuff
Member
Turns out it was just the clutch fan. Those M50 engines are so damn strong.
I'll keep an eye on it over the next few weeks but so much happier with it now.
Next time too I'll YouTube the work. Got stumped a few times. Cracked the fan nut but it didn't look like it was coming out. I forgot you can hand turn it out once the nut the cracked.
The allen key got removing the bolts was a mission too. I think that clutch has been in there for 120k miles. Needed a long allen key to get leverage to remove the bolts.
Then the clutch looked like it was part of the fan housing, stared at it for 20 mins trying to figure it out before I palm slapped it on the grass. Was nice and easy at that point.
drove for 45 mins at 20mph for a chunk then some 50mph roads, then back to 30 roads. No boiling coolant any more.
Member
some people are too quick to expect the worst and a cooked head gasket.
my few observations on cooling sys over 19 years. temp arrow twice gone into red and not noticed for as much as 5 minutes. first time wp impeller seperated-was factory pump failing at 50k miles. 2nd time found had forgotten to routinely topup on my 2 weeks schedule-because i could not verify source of slow leak- and so while idling a couple minutes went red. system was a quart + low only. also have had a replacement graf wp shaft break after 45k miles and drive viscous fan into radiator and that time useless to notice to look for red.
last week caught in freeway jam for 15 minutes, boiled over in steam cloud , was able to shortly exit freeway, keeping aircon off, heater on maximum blast, rev's up, and avoided needle in red. my oem nissen standard rad had a broken neck at 50 k miles. it joins prior 2 behr oem failures but they lasted longer than the nissen. and beleive me i baby the plastic necks with loving care. plastics on this old model e36 are cr+p. have another behr oem rad on order. still no symptoms of water in motor lube system. (once had a mazda with cooked head gasket, been there done that.) so, others have avoided serious h gasket damage-good luck. my present genuine oe bmw wp with 90k miles looks perfect, however i am replacing it with another since i am replacing several other parts anyway.
Driver
The bigger question there ^ is how you don't notice a bright red warning light on your dash for 5 mins... lucky it wasn't your oil pressure light!
'96 M3, S50B32, 6MT
+ good stuff
Member
i can amaze myself sometimes with my inattention.
btw, general opinion ? have pondered for years. while i know to shut engine when see red and any time is too long, have never noticed opinions for how resistant to overheat durations for these e36 engines. any case examples out there? anyone else?
Driver
There are all sorts of horror stories about e36's overheating and instantly warping the head... in my experience this isn't the case. Of course overheating any engine is bad but I don't believe e36's are a particularly special case or any kind of exception.
General rule of thumb is that if you see the coolant overheating warning light then immediately coast to a stop (in a safe place) and let the engine cool down (this will take quite some time). You've probably not done any permanent damage. Then you need to establish what caused it and proceed from there. Ideally you'd notice the temps increasing and stop before the warning light.
It is not a given that if you overheat the engine you will do permanent damage.
'96 M3, S50B32, 6MT
+ good stuff
Member
thanks for repiy. my 3 to 4 experiences over 20 years fits with your opinion.
Member
No coolant decrease so far, car is looking good.
Next job will be fixing the driver side window. Ugh! Not looking forward to that one.
Member
Update:
I checked the coolant today after giving up on the window. No coolant loss at all. Woohoo!
Member
Exactly. A big red light turns on that is never on at any other time after Key ON. Red lights never go unnoticed.
Member
Your expansion tank cap is probably bad. Also how old is your antifreeze, people forget it's not just for freeze protection, it also raises the boiling point .
Attn. NEWBIES: Use the search feature, 98% has already been discussed.
Click the search button, select "search single content type", select the "e36 sub forum" specifically, try the "search titles" then try the "search entire posts".
Member
Coolant age was a day when it was happening. Went through 20l (coolant and distilled water) when this was happening
Posting Permissions
Reply With Quote
Bookmarks