Overheating Issue

[Campagnaj]

I have a '92 325i with the M50. A couple of months ago I was idling at a stop light and my radiator blew up. So I pushed it to my house (like 2 blocks away). Two days later the car had a new radiator. A week after that a new thermostat, radiator cap and overflow bottle. Now, my car likes to start getting above operating temperature at an idle. I figured it could be my fan clutch, however that was replaced a few months before I purchased the car (not even a year ago). So I ohmed out the coolant temp sensor (or aux fan switch sensor) and didn't get a reading. I replaced that, hoping it would fix the problem. No dice. Now, I don't know if the water pump has been replaced or not however I would assume so as my car has around 150k miles and they are known to go around 100k.

My question to you guys though is, what do you guys think: Water pump or early stages of a head gasket? Oil is fine, no white smoke, just running above operating temperature.

[gk325is]

Have you tested the AUX fan again since changing it to see if it is working?

[granlund]

Did you properly bleed the air out of the coolant system? It's a bit tricky on the BMw I6's.

Park on a steep uphill, start the engine, heater on max, rev to 3000 with the bleed screw open until it stops bubbling. Fill reservoir if needed and repeat.

If the car is on it's original waterpump, it's a ticking timebomb ready to go any second. Replace immediately!

[Pdwight]

All of the above, make that head-gasket your last stop

[flyfishvt]

DO NOT assume anything with these cars. If you don't know if the water pump has been replaced then it needs to be. If you open it up and find a metal one in there then take the new one back for a refund. Your radator could have easily blown up from a faulty water pump. The symptoms of a bad water pump and clutch fan are almost identical.

The sensor you replaced in the radiator is a temp switch. unless the car is overheating when you test it then you will get a zero reading on it with a meter. So you probably replaced a good switch.

[Campagnaj]

Have you tested the AUX fan again since changing it to see if it is working?
Yeah the fan works, I know that because when I jumped the connector to the switch it turned on and ran both speeds. I honestly though, don't remember if the fan turned on after I replaced it while the car was running hot.


Did you properly bleed the air out of the coolant system? It's a bit tricky on the BMw I6's.

Park on a steep uphill, start the engine, heater on max, rev to 3000 with the bleed screw open until it stops bubbling. Fill reservoir if needed and repeat.

If the car is on it's original waterpump, it's a ticking timebomb ready to go any second. Replace immediately!
I did bleed it however not as you described. And I'm waiting to hear back from the previous owner, I don't feel like spending $35 on a carfax and finding out that he did it in his garage.


The sensor you replaced in the radiator is a temp switch. unless the car is overheating when you test it then you will get a zero reading on it with a meter. So you probably replaced a good switch.
I put the sensor in a cup of hot water and tested it. I didn't test it cold.

[BMWMPow3r]

+1, you also need to bleed it several times in the course of a week to be sure. Also, it could be a fan temp sender on the radtior. does your aux fan come on during overheating? Could be clutch fan.


Also, a plugged cat will also cause overheating and issues with anything over 2k rpm. My cat was so bad, I couldn't even free rev it past 3k.
With the foot down in neutral the rpm would hover at 2.5-3k.



Have you tested the AUX fan again since changing it to see if it is working?

[Campagnaj]

+1, you also need to bleed it several times in the course of a week to be sure. Also, it could be a fan temp sender on the radtior. does your aux fan come on during overheating? Could be clutch fan.


Also, a plugged cat will also cause overheating and issues with anything over 2k rpm. My cat was so bad, I couldn't even free rev it past 3k.
With the foot down in neutral the rpm would hover at 2.5-3k.

It wouldn't, however today I just replaced that sensor. It's on the left side of the radiator a little above the middle by the reservoir, right?

Plugged cat is a possibility... My car was running VERY rich for about a month until I replaced the idle air control valve + hoses. It only increases in heat at an idle though, which would point to a problem with the fan (and taking into account with what flyfishvt stated, or a water pump).

Also, I do remember the previous owner telling me the fan clutch was recently replaced and the heads were re-done about a year ago at BMW. The previous owner was a good friend too, so hopefully he didn't just bs me.

Ok, just drove around the block, let it get to operating temperature then waited to see what would happen. It started to exceed operating temperature slowly and the aux fan DID NOT turn on, even with the new sensor. However I know the aux fan and connector to the sensor work because when I put a wire in the sockets, I can get both speeds.

[BMWMPow3r]

With my plugged cat. the car would start to overheat at drive-thrus, etc.
theres 2 sensors on the rad, yes by the reservoir. Running rich could cause fuel to dump into the cats and melt the face of the filter element. In my cased it was a bad ecu I was forced to use for a few months.

with all my issues, only the front of the element was melted about 1/2" into it. But that was enough to burn up piston rings, warp head, blow head gasket.

[Nomade30]

With the cap off starting from cold, start the car with heater on full blast. Hold the engine at 1500-2000 rpms, open the bleeder. Keep pouring in coolant and let it bleed until no bubbles(and i mean NO BUBBLES) come out.

I have used that method and I've never had a problem with air bubbles, started using it about 2 years ago and it's spanned over numerous bmw's without fail.

[Campagnaj]

Well, honestly I just hope it's only the water pump. I'm going to stay off of it until I get paid again and can replace the water pump and drive belts (starting to crack, might as well replace with the fan out of the way).


With the cap off starting from cold, start the car with heater on full blast. Hold the engine at 1500-2000 rpms, open the bleeder. Keep pouring in coolant and let it bleed until no bubbles(and i mean NO BUBBLES) come out.

I have used that method and I've never had a problem with air bubbles, started using it about 2 years ago and it's spanned over numerous bmw's without fail.
Will do in the morning.

[gk325is]

Ok, just drove around the block, let it get to operating temperature then waited to see what would happen. It started to exceed operating temperature slowly and the aux fan DID NOT turn on, even with the new sensor. However I know the aux fan and connector to the sensor work because when I put a wire in the sockets, I can get both speeds.

You just found your issue, the AUX fan is not working. Go though and check the wire connections and fuses for the fan. It should turn on when the car gets hot so this is your first issue. Fix it then move on.

[Campagnaj]

Alright, today I bled the coolant. No bubbles appeared. I idled it until it rose above operating temperature. I put my hand on the valve cover and it wasn't burning my hand. I've done oil changes on cars that were a whole hell of a lot hotter than my valve cover. So that prompted me to get an infrared thermometer and check the temperature. I aimed it at the thermostat housing and it read around 190 degrees Fahrenheit. I asked my father, a master tech (however not master on Euros), what the general operating temperature is for an engine. He said around 210 and an engine when it is overheating is running above 230. Well, I checked the thermometer again, 196. Then I revved it up and got it the gauge to read that it was overheating. Checked the temperature, 211. Then I looked up where the engine temperature sensor was and found that it was underneath the intake manifold. I then unplugged the sensor, the gauge had no reading it was beneath the blue on the gauge. I grounded the sensor and it slowly went all the way into overheating however the red light indicating that the car is overheating on the gauge did not turn on.

What I am thinking is happening is that since the vehicle already overheated and blew the head once and then overheated and blew the radiator, the sensor is busted. Therefore when the gauge reads that it is hot, the actual temperature of the vehicle is much lower, low enough in fact to keep the thermostat closed and the aux fan off.

I've ordered a new engine temperature sensor and it should be here on Monday. I'll keep you all informed as to how she is doing or any new developments haha.

[freddybeemer100]

Do you have the plastic thermostat cover? If so, it's time to replace that with the aluminum one with a new thermostat as well.

[granlund]

If you're still on the original waterpump, or do not know when it was last replaced, I suggest changing it now before you warp the head. The impeller breaks off the shaft and does not turn to pump any, or very little fluid.

Was the water gushing out when you had the bleed screw open? If not, the water pump is not pumping any fluid.

[flyfishvt]

Just an FYI..that sensor you tested is only for the gauge. The DME has its own sensor on your car. If your radiator blew it sounds like you have some real overheating issues and not just a faulty gauge. To get a true reading of the engine temp you should use a scan tool that can read live data and see what the DME temp sensor is reading.

[Campagnaj]

If you're still on the original waterpump, or do not know when it was last replaced, I suggest changing it now before you warp the head. The impeller breaks off the shaft and does not turn to pump any, or very little fluid.

Was the water gushing out when you had the bleed screw open? If not, the water pump is not pumping any fluid.
I found out through the previous owner that the water pump was replaced when the heads were redone.



Do you have the plastic thermostat cover? If so, it's time to replace that with the aluminum one with a new thermostat as well.
I made sure to get the aluminum housing. It's on the vehicle.


Just an FYI..that sensor you tested is only for the gauge. The DME has its own sensor on your car. If your radiator blew it sounds like you have some real overheating issues and not just a faulty gauge. To get a true reading of the engine temp you should use a scan tool that can read live data and see what the DME temp sensor is reading.
Well the problem is, the gauge is getting a false reading. The car runs at normal operating temperature while the gauge says its overheating. I've essentially replaced the entire cooling system minus the water pump. That's what prompted me to check the gauge.

[Pdwight]

A stupid simple question, if you run it with the reservoir cap off and let it warm up...does it boil over ??

The Aux fan should come on before it boils over

[gk325is]

A stupid simple question, if you run it with the reservoir cap off and let it warm up...does it boil over ??

The Aux fan should come on before it boils over

Boiling is relative to pressure, it may boil over with the cap removed at regular temp as boiling point is 212 degrees ish (depending on altitude). With the cap on the pressure in the system keeps the water from boiling as it is under pressure and the vapor has no where to go. This is all assuming water is in the system (which is isn't) because I dont know the boiling point of the bmw coolant.

[Pdwight]

Well even given the boiling point of water this would be a good test to see if the Aux fan comes on, certainly at 212F it should be on before it starts to boil.

[Nomade30]

Coolant will boil with the cap off even with the aux fan on. You need the pressure to keep the cooling characteristics of the coolant system.

[Campagnaj]

Alright guys, I know it's been a while since I updated you, but this is the last update, unfortunately.

What happened:
I got a new job with better pay and full bennies. On my first day, I was making the commute (about 25 miles). About 10 miles down the car starts to overheat. I pull off to the side of the road and check the temperature manually. It read 170F @ the thermostat and I needed this job cause I had quit my other one an hour beforehand. So I said f-it. I cranked the car and it didn't start. Check engine light comes on. I crank it again and it fires up, the check engine light goes off. I drive it about 4 more miles and I hear a pop. I figured I blew a hose or something. I call up my father, he helps me get it off the freeway and we take a look at the car. The new overflow bottle had burst. Well I get to work ontime thanks to my father and then I stay with my brother for the week, cause he works close to me and we carpool. Well it's the weekend and now I can check out my car. I cranked it in the morning and it wouldn't start. Two options: bad starter or hydrolocked cylinders. Pulled the spark plugs out, cylinder 4 was filled with coolant.

My head must've blown when the radiator did. Ever since that the car would run like shit when I'd start it up in the morning, then go away when I accelerated and wouldn't return until the following morning or after it sat for more then say 10 hours. Because the head gasket was blown it would shoot pressure out to other parts of my coolant system i.e. blowing the new overflow bottle.

When I purchased this car, I had planned on restoring it. The front door panels were bad, the paint was bad, the seats were worn, the power steering pressure hose had to be replaced, etc etc. I was going to restore it because I had all the tools to do it myself. However I don't have the tools to rebuild the engine and I don't want to pay someone a couple grand to fix the engine. So today, my dreams for this car have died. I'm going to buy a new e36 and part out the one I have now :|

[flyfishvt]

Sorry to hear that. Don't feel too bad. You had a ton of work ahead of you to fix that one up. I bought a project car and it ended up taking 2 years and at least $3500 to get it back to decent shape.


Yours was/is a 92 so its about 20 years old. That's a lot of years for any car.

[Campagnaj]

Yeah I knew I had my work cut out for me when I bought it. Just didn't think that with a 92 head in there it'd blow cause everyone that knew anything about e36s that I talked to or worked with said that the head was bulletproof haha.

I got my eye on a 318ti right now just cause the price is right for what it has. I'd really like another 325 or 328 but I just need a car now haha.

[flyfishvt]

Be as patient as possible and wait for the right deal. They are out there. I just picked up a 97 328 vert for $2000. Its got nothing with being in the right place at the right time. It has everything with being ready to pull the trigger when you find the right car.

[Campagnaj]

Well this one has a really nice blue paint job, supercharged and nice rims. I emailed the seller (no phone number) and am waiting for a reply. I obviously want to check it out and go for a test drive. They're asking $2330 for it though.

I did get a nice laugh though from some guy trying to sell his 98 328i for 20 grand without a single picture or any info on it.