overheating and cannot find the cause

Miles...u day man!

I feel so inadequate next to you! But I'll recover!

I'm on phone so if I wrote something stupid, it was probably the phone!

I have exactly the same symptoms as gskinlow experienced. I searched the posts and forum thoroughly and still need some advice.

Prior to maintenance, I had coolant light coming on intermittently in cold weather. I replaced the leaking thermostat housing with aluminum aftermarket one(ebay-deutscheparts) and the water pump. After replacing those, I replaced the oil pan gasket which I wanted to do for a very long time because it was leaking.

The oil pan gasket is now tight and I checked for leaks several times, no oil leak. I put 6.1 qt. of Valvoline Synpower 5w-30. I checked the oil level on the dipstick, its between the notches, close to the top notch (although 0.8 qt. lower) (Cleaned with a towel and inserted second time to read the oil level when engine is cold). The new thermostat housing leaked from the bottom left, so I put some black silicone, tighten the bolts and let it cure for an hour before filling. No coolant leaks from the thermostat housing now.

The overheating problem occurred after replacing those. First, I bled the system a couple of times after a partial refill. However, the car still overheated after driving 20 mins. I tried it with a/c on and off, after 20 mins it starts to overheat. After reading mkodama's instructions and many other posts, I completely drained the system and refilled it, bled it properly by doing cold and hot bleed. I changed the mechanical fan clutch and made sure the fan blades are facing the correct direction. Thermostat seems to be working because lower radiator hose becomes hot after 20 mins, but in the beginning it stays cool. Still overheating after driving for 20 mins.

I checked the voltage on auxiliary fan connector, it's 11.66v with the ignition on, 5v for the temperature sensor cable on the lower radiator hose and the resistance for the sensor is 2400 ohms (its said to be between 2-3K ohms?). I could not read the frequency on the green/black wire (it's said to be between 10 and 100Hz, pwm square-wave) on the aux fan connector.

The auxiliary fan is on when a/c runs however I am not sure it works intermittently or not(I read several posts about it). I took the electrical tape off and examined the cables(red,brown,black/green) close to aux fan connector, no rips or disconnection. The expansion tank cap is old and I think I always over-tighten it to stop leaks from the cap. I am gonna replace it today however, it was not an issue before (I read it may trigger the coolant light due to pressure).

The engine overheated on the red line for a min or so after 20 mins of driving on the highway when I tested it for the first time but no oil in the coolant. I don't think it's the head-gasket however I still cannot find the culprit.

gskinlow, you must have fixed your issue by now. What was it?

Any input will be appreciated.

Originally Posted by Elwin

Do you have Automatic or Manual?

If you have manual you would have two electric fans. Check if they start when you car gets hot. There are two fans - in the front of radiator for the A/C at the back for the engine.

If automatic A/C fan is electrical and engine fan is mechanical driven by the belt and mounted on the water pump. It has viscosity clutch. When your car gets hot clutch must engage and fan must start spinning full force.

If you have a lot of pressure in the cooling system then this is a head gasket problem. Sometime no water is in the oil, but water disappearing though cylinders. Sometimes ini this case you can get hydro-lock when starting the car.

i am having the same problem,
mine is automatic fan does not go full force?
should i replace the fan or could it be a sensor?

Bleeding the system doesn't involve starting the engine. Where did this come from? Car level and ignition on with heat selected (not started). Remove the bleed screw. Fill until it comes out the bleed hole. Stop and wait as the level will drop. This is the air being expelled! add more until the level stops dropping. Voila!

AFAIK, the pre/post area around the thermostat is not airlocked. In other words, this is why bleeding the car cold is perfectly fine. Hell, worked for me. Besides, TIS backs this up 100%

Legend for newbies;
ET - Expansion tank
WP - Water pump
TH - Thermostat housing

After changing almost everything related to the cooling system, problem still existed. The only two pieces I changed prior to overheating were the TH and WP. I did not want to blame the recently replaced thermostat and I kept changing parts, what a mistake !

However after replacing the already replaced thermostat, I bleed the system according to the cold&hot instructions once again. That's when I realized how the thermostat works. (More experienced mechanics can correct me if I am wrong) The hot coolant is pushed into the radiator from the ET-radiator connection close to ET cap, that's why radiator gets hot close to the ET connection at the beginning, and the rest of it stays cold till rest of the hot coolant fills in. After the radiator is totally filled by hot coolant, (that's when the lower hose gets hot) the temp gauge on the lower hose reads the coolant temperature and the thermostat opens. If you have a faulty thermostat, the WP keeps pushing the coolant but fluid never circulates inside the engine, only between the ET and the hoses. Excessive pressure builds up in the cooling system (not in the engine) and EP explodes (what happened to me).

A useful tip: some owners (i.e. Paraklas) used high-temp silicone which I think is really useful however you don't need to use it all over the thermostat housing area. If you just put a thin layer of high-temp silicone all around the TH gasket, it will stop the leaks. Do not over tighten the screws to stop the leak. Not only it won't do it but also you may snap your screws. When I replaced the TH second time I realized I over-tighten the screws which got stretched and thinner but did not stop the leak. Use silicone, do not over-tighten, be careful!!!

Cold bleeding works if you properly drain the system from the drain hole under the engine. It's close to the engine bracket on the passenger side.

An air bubble when starting cold is none of the things described above - it is compression going into cooling system. Some times coolant goes into cylinder - sometimes compression goes into coolant - 7 out of 10 times its compression into coolant and well, that will make it overheat evertime.

BEst way to bleed cooling system - I've down over a 1000. Raise front up, heat on front defrost full blast. Fill cooling system with bleeder screw cracked open. Fill until bleed screw leaks coolant. Start engine - top off coolant. Rev up and down and up and down and hold at 3500 for 15 seconds. Rev up and down and don't stop until there is heat from defrost - a lot of heat and be sure to top off and put cap on before thermostat opens or it all comes out. Test drive - let cool - check level and add or subtract if needed.

If you don't rev up and down air WILL be trapped in heater hoses, water valves and heater core. The engine might be bled but the cooling SYSTEM won't be.

hey Dmax ... Ive read tons of threads in here until my eyeballs pooped out almost literally and i always see your name and your responses are the most helpful. I was trying to see if you could give me any insight on why baby is overheating...(2000 bmw 323i 4dr m52)

water pump failed on highway two weeks ago, as soon as temp gauge on cluster spiked i pulled off highway and parked at 7/11.
got car towed to my house.

work done since (DIY)
*new water pump
*new thermostat and housing
*new fan clutch
*used BMW "blue" coolant
*bled per YOUR method
(also replaced valve cover gasket as it had a leak and new plugs and lubro moly oil)

here's the problem the car still overheats then the next day when i went to move it from driveway to my garage it started in limp mode.

I pulled off the throttle body and cleaned it and i was running good (limp wise) took for a test drive and still overheated and limp mode is now intermitent.

I am totally at my wits end and am hoping you can give me insight towards the overheat and limp mode issue and if you know if the over heating would cause limp mode.

any ifo you can pass along would be great

thanks

Mike

also no oil in my water/ no water in oil and no smoke from exhaust!

hey Dmax ... Ive read tons of threads in here until my eyeballs pooped out almost literally and i always see your name and your responses are the most helpful. I was trying to see if you could give me any insight on why baby is overheating...(2000 bmw 323i 4dr m52)

water pump failed on highway two weeks ago, as soon as temp gauge on cluster spiked i pulled off highway and parked at 7/11.
got car towed to my house.

work done since (DIY)
*new water pump
*new thermostat and housing
*new fan clutch
*used BMW "blue" coolant
*bled per YOUR method
(also replaced valve cover gasket as it had a leak and new plugs and lubro moly oil)

here's the problem the car still overheats then the next day when i went to move it from driveway to my garage it started in limp mode.

I pulled off the throttle body and cleaned it and i was running good (limp wise) took for a test drive and still overheated and limp mode is now intermitent.

I am totally at my wits end and am hoping you can give me insight towards the overheat and limp mode issue and if you know if the over heating would cause limp mode.

any ifo you can pass along would be great

thanks

Mike

also no water in my oil and no water in oil and no smoke from exhaust

Sure, Mike.

But first, don't insult the morons around here by calling just for me. There are one or two that think they know more than me so they feel better if you don't ask for just my help. Biggest issue is that you'll get 'just' my help and I'm old, forgetful, and prone to trolling for no good reason.

Of the things you did replace, in particular the thermostat...was any of them after market. If therm was AM, it's immediately suspect.

You didn't replace the ET, so that's another possible leak source, but if you're not leaking...leave that be for now.

Even though you used 'my' method for bleeding, I've posted the two methods quite often...more recently the 'quick' rev to 4K rpm method...so try that if you didn't...or try it again and again if you did...heater on, fan on, right?

When are you overheating...immediately right to overheating, or when slowing down after being at speed and 'okay' temp wise?

Is it possible the temp sensor went bad due to the overheating causing a bad temp reading leading to the car's computer putting it into limp mode. Just an idea.

thanks for the replies !!

as far as the overheating the temp gauge starts to go up after about 10-15 min test drive or less depending if its night(cool) or day (hot)... and it increases when i slow down and or stop but goes back down when i accelerate again, but then goes back up if i keep driving. (which im too scarred to do just back to the house from the neighborhood test drive) therm is AM new from napa. i tried both bleed methods with the revving and without and have bled numerous times. as far as the limp mode im clueless as to what is causing that. since ive been working on the card i have not drove it more than test drives arount the nieghborhood. also when i do pop the hood after it reaches a higher temp and i shut down i can hear some gurgling in the RAD and ET area and a light hissing sound so i sprayed distilled water in the area to see if i could hear or see a leak and nothing was noticed.

See? That's exactly what I mean. I was thinking temp sensor wasn't replaced when I wrote that detailed post to you...but I forgot!

Yea, never a good idea to ask for one person's help. Few here are 'real' mechanics and there's a big difference in 'talking' about fixing vs. being there fixing.

Thank you silver! BTW, I have to say, that user names like yours are the hardest to remember. you know there will be a 2001silver330i 2000blue330i. You need something catchy and you're new enough here there's hope for you.

One fanatic in NJ had a name like that...forget it...but in my mind I call him "youngwhiteguy" and so I never forget him.

Silver, would you think about it? If you tell us something about yourself and include nude pic of Marisa, then maybe I can turn you into a memorable fanatic! Griffin, Gheybe, Albeeee, Smuuuuv, Bimmersgarage, Delmarco, Mango, Cyberkaa+, MJ, Havesexwithtrains, Ilovebeagles...names like that, names people can remember. You deserve it so get on that, will ya?

Temp sensor is distinct possibility.

Also, soon, I have to say, you'll hear, 'replace it all' and to save Mango the trouble, I'll say that for him. Whatever you haven't replaced, go ahead and replace. That sensor, hoses, trans cooler.

There, now that that's out of the way, I'll go back to bleeding. You've opened up the system at the wp. If it has air in it, it won't pump coolant, just air. Ah, also try the burping method...squeeze upper hose.

Your WP is, I believe, cavitating. Mkodama has said he has good success with the car up on an incline a bit.

I think you need to rev with cap and bleeder closed, heater on, rev to 4K rpms for 20 secs. and turn the car off.

Start bleeding when the car is cold, fill to between min and max, close cap and bleeder!

will try the burp and re-bleed on incline with car cold after i burp. if the issue persists i guess i should have it towed to an indy to atleast have the sensors check threw the computer right?
also any idea on the limp mode issue?

thanks

Oh, limp mode...I don't have an auto, so don't know a lot about limp mode, but if I'm not mistaken, I just saw a thread where bad therm was related to limp mode...guess the trans fluid doesn't get cooled down enough or something (vague recollection).

Anyway, cross posted I see...my new diagnosis is your AM therm. If you've read other posts of mine, maybe you only filled with water until you knew you were good...but in any case...get a real therm...OE...wahler iirc. If you can't wait to find out I'm right, take off the therm you have now, remove the thermostat from inside of it, and return just the housing...then go through the bleeding process again.

That was easy!

Next!



JK...no more cooling threads for me...Mango has the answer...very easy, often perceived as obnoxious answer, but it's not. If you're not a mechanic but can remember left from right...replace everything! Basically what I said, but much more politely...and with more specificity!

I hope no one who knows me has read all this! I don't need to hear it...I know!

yeah when went to limp mode the trans light on my cluster didnt show up just the EML and traction which i thought was the TB and/or tps sensor, which is why i pulled and cleaned it. so what ur saying is run the car without the them (only the housing)to see if thats the faulty AM part causing the issue?
thanks

Well, that's about it for now...not sure there's a way to 'lock therm open' electronically without removing it.

Oh, also, first find out if you can do that with your therm. You probably can, but I'm not sure. You can with a wahler.

And, I'd also suggest you really spend more time reading. You've made too much sense. Before really working on the car, you need to throw up.

thanks i will try to burp and try the thermo trick before i pay the indy shop i found the $70 to diagnose (which isnt bad) just wanted to DIY for knowledge and ego lol !!
i did find the wahler online for a good price (only 410 more than the AM) so ill most likey return the AM as its 1 yr warrenty and put the wahler in regardless!!
will let ya know the outcome tomorrow

thanks so much !!

Mike

p.s. i'm about to throw up NOW~~ haha

**** $10 more than AM therm