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-   -   overheating and cannot find the cause (http://forum.e46fanatics.com/showthread.php?t=825186)

gkinslow 02-23-2011 12:26 PM

overheating and cannot find the cause
I have a 2000 323i automatic that is overheating,and I can't find the problem. I replaced the water pump about 5 months ago. A couple of weeks ago I noticed my low coolant light on so I added a bit of water. This became regular; I found the leak was a crack in the expansion tank. Every since I replaced it I keep having to add a bit of water to it after a long drive. I checked for leaks everywhere and the only place I have seen a leak is from the radiator / expansion tank cap. The other day I added water to it before leaving work. Then started driving home which is about 50 miles. About half way there the car started overheating. I pulled over, popped the hood and found water spueing from around the radiator cap. I grabbed a rag and was able to turn it just a little bit tighter. This stopped the large amount of spueing, but the cap is on so tight it's crazy. I changed the thermostat yesterday and filled it with coolant per the many, many instructions I have found so as to try and not get air pockets. The car still overheats. At one point last night after it had cooled, I started the car and let it idle. When I saw it get close to normal operating temperature I drove it around the block. As I was pulling back into my driveway the temperature gauge was rising closer and closer to the red zone. I got out in my driveway and noticed that the electric cooling fan was not running but my mechanical fan was going fast. After about 2 hours of cooling I checked my water level in the expansion tank and it looked ok. No water in the oil, no leaks any where but still overheating.

danewilson77 02-23-2011 12:39 PM

System has never been properly bled.

Did you also replace the T Stat?

E46007 02-23-2011 12:49 PM

I would start with properly bleeding the system. Then Thermostat...

Drew@Swift Motorworks 02-23-2011 12:50 PM

Replace that cap. It's not meant to go on that tight and over tightening can damage the seal.

Id suggest you try to bleed the system again

Elwin 02-23-2011 12:56 PM

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.

gkinslow 02-23-2011 12:57 PM

I've bled the system many times. I replaced the thermostat as well as the expansion tank, and the radiator cap.

Drew@Swift Motorworks 02-23-2011 01:11 PM

What about the radiator? Didn't you mention it was leaking?

dmax 02-23-2011 02:22 PM

Hey Drew!

He said radiator/expansion tank cap, and then referred to radiator cap, so think he meant 'leaking from the cap' but...

I was wondering what you were...radiator.

OP, which of the many, many bleeding instructions did you go with?

Also, when your system was overheating and spewing coolant...I know you were trying to do what you could to save coolant and thus your car, but as a result of that, you also trapped pressure in a system that otherwise wanted to release it.

The ET cap is a pressure relief valve...blows at 2 atm, I believe. The seal is two o-rings in the cap and a little gasket at top. It's not made to be tight at all. When it stops turning, so should you.

Just saying don't do that again...and I hope your car turns out fine.

Find the leak is all I can say. Clean things up, run distilled while you're hunting to find issue. If coolant is older than 2-4 years, might as well drain completely.

Read more threads...you'll find it. Could be bad hose connection...leaking bleeder screw fooling you...leaking radiator.

gkinslow 02-23-2011 05:14 PM

I stated radiator cap because many noobs my reference as so. I know that it's a coolant expansion tank cap. I did read that is was a pressure release cap; approx 2 bar or 30psi. I just got home with another new cap. I exchanged the one I just purchased. The dealer didn't want to but I started making a scene. The way I have filled it is removed the bleeder screw, then turned key to the on position. Next I turned on the heat to 91, blower on low. And slowly proceeded to fill the expansion tank until the level indicator is at max position on some fluid had came out of the bleeder screw hole. The I cap the tank and replace the bleeder screw and start the car. I let it come up to normal operating temp and shut it off. After the car has cooled I open the bleeder screw and remove the et cap to check the fluid level. I've added fluid as necessary. After doing this 2 to 3 times, I have driven it and it still began to overheat. I stop the car and look under the hood and you can see the fluid coming out from under the et cap hissing and what not as well.

Before making this response I have just done this procedure again but this time with the front of the car on jack-stands. I have allowed it to come up to temp twice but each time as soon as it gets to temp I shut it off and check the fluid. So far it's looking ok. My secondary fan, the electric fan, I have proper voltage to the connector that's on the fan shroud but what is the control voltage for it? 5v, 10v, or what? Anyone know? I do not think it's running when necessary and I would like to check it. It turns freely by hand. What I read in the manual is that its speed is controled via pwm, but I know you should be able to apply a steady voltage within its operating range and have the motor run.

TrickTizzle 02-23-2011 05:25 PM

Not reading all of that.

Did you bleed the system?

dmax 02-23-2011 05:38 PM

You have the dial between vents to three red dots when you bled?

Also, you don't open up bleeder to check the level...and you don't check the level when warm...you check when cool.

Lubricate et cap with coolant whenever you put it on.

Also, when filling system...on level ground...you'll have the ET filled to the brim at the point that fluid comes bubble free out of bleeder...which doesn't have to be removed, just turned a little bit.

If you fill to max only, and not all the way up to the top of the filler next while filling after cooling work, you won't have enough coolant in, and I suspect that was your initial issue...maybe combined with an air bubble.

gkinslow 02-23-2011 07:29 PM

Well my electric fan is working.

Yes I have bleed the system.

I do have the dial in the center of the vents with the 3 red dots showing. When I remove the cap again I will be sure to lub the et cap seals with coolant. I have checked it before with it cool, but I believe that each time I did I had opened the bleed screw prior to removing the et cap to check the fluids level. I am waiting for it to cool right now. When it is cooled I will check the fluid level again without opening the bleed screw. I have before, and earlier today, filled the tank up to the top of the filler neck until fluid came out of the bleed screw. At which point I closed the bleed screw. Then capped the tank and warmed the car up and then fluid comes spewing out from under the et cap. Then I have to do it all over again because when it cools.. a little.. the low fluid level light is on. So I do it all over again. It almost seems like the cooling system is not fully circulating

dmax 02-23-2011 08:09 PM

When you're just adding a little coolant, you don't need to go through entire bleeding process...just add to right level when cool.

You need air above coolant in ET tank, otherwise it will tank, coz it's not able to cushion the expansion.

Careful...think you should take my advice and read threads until you throw up...you sound perfectly fine to me...so I don't think you did that! lol

Sorry...cooling system is a challenge for many...and for many reasons!

Do not overfill...that's particularly important...so why I also say fill to between the min and max mark to be safe.

GL OP...got to get to bed as I'm old!


E46330iguy 02-23-2011 08:15 PM

What she said :eeps:

Originally Posted by dmax (Post 12846571)
When you're just adding a little coolant, you don't need to go through entire bleeding process...just add to right level when cool.

You need air above coolant in ET tank, otherwise it will tank, coz it's not able to cushion the expansion.

Careful...think you should take my advice and read threads until you throw up...you sound perfectly fine to me...so I don't think you did that! lol

Sorry...cooling system is a challenge for many...and for many reasons!

Do not overfill...that's particularly important...so why I also say fill to between the min and max mark to be safe.

GL OP...got to get to bed as I'm old!


dmax 02-23-2011 08:23 PM


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

gkinslow 02-24-2011 08:45 PM

Well I let the car sit all last night, and this morning I checked the water level without opening the bleed screw. I had to add about 1/4 gallon of coolant till it came up between min / max level. I then started it and let it idle for about 5 min. I then turned the car off and proceeded to leave for work in my other car. I didn't check anything under the hood before I left. Well the car sat for 10 hours before I got home and cranked it again. When I tried to crank it gave me a hard time but after a few seconds it started. As soon as it did I heard steam, hissing, and water coming out from the et cap. I looked under the hood and coolant was around the cap. I had my wife start it and as soon as it started cranking coolant was coming out; and the cap is on tight. The engine was stone cold and even the coolant coming out is cold. I removed the cap and had her just turn it over and as she did coolant started blowing out like something pressureing the coolant out.

Would this be a blown head gasket? The compression blowing into the coolant system? When it was idling this morning there was white smoke coming out of the exhaust. I was just hoping it would be excess fuel or something.

gkinslow 02-24-2011 09:26 PM


dephantn 02-24-2011 11:02 PM

I have idea that your radiator is blocked by debris or gunk. And when the engine cold, the coolant should not come thru radiator because the thermostat must be closed, so may be the thermostat open /close inappropriate ( some time the new one defaulted) ?

dmax 02-25-2011 04:59 AM

Although I think it was just an air bubble passing out of the system, it's hard to know for sure.

You don't need to think head gasket yet, unless, you know, you've overheated the engine.

The slow to crank sounds like battery, so check the car's voltage off and on.

Also, nothing personal, but without searching you and all your posts, I have no idea of the status of your car basic maintenance-wise...so would suggest you become addicted to fanatics and start learning lots. Even if you don't have issues beyond what you've mentioned, you will (sorry...but you will), and the more you learn about the car, the more secure you'll be, both mentally and mechanically!

...and then there's this thought I have...and I hate to mention it.

You went to dealer and made a scene and had them give you another ET cap. I don't understand how your starting it would add any pressure precipitating the leaking from the cap...so I'm thinking either a bad connection there (did you clean the inside of filler neck...lubricate cap's o-rings with coolant?) or a bad cap (coz you made a scene (low odds I think)), or because the upper hose is leaking and you think it's the et cap?

Maybe that connection...reused since replacing the ET...might be bad?

I think you're just getting the result of a leak from other than where you thought...and the WP pushing coolant around...and it pushed through an air bubble which is why you were low and needed a qt...and that air bubble 'might' be because of a leak...not just cap.

Finally, white smoke at start up is probably a sign you haven't driven the car enough...and also explains the slow crank. Starting takes a lot of power, so last night, on a presumed low battery, you started the car and let it idle for a little...you lowered battery further.

Long drive will hopefully charge battery fully, and also dry things up and clean things out...but hold on that driving until you sort this coolant issue out.

mkodama 02-25-2011 06:32 AM

You still aren't bleeding the system properly. I can tell because you said the coolant started coming out when you cranked the engine cold. Does the coolant level also go up and down with engine RPM? This means there is a big pocket of air inside your engine or the hoses, and when the water pump moves, it is just pushing this giant bubble around. The exact same thing happened on a friend's car. This is a situation that only happens when the cooling system is partially emptied and then refilled. If the engine was completely drained of coolant and then refilled, this doesn't happen.

Here is what to do:
1. Turn your car on, heat to max, blower on so that you can feel warm air if it starts coming out.
2. Open the the expansion tank cap, and poor in coolant to the very top.
3. Start the engine, prepare for some coolant to overflow a little.
4. This is the special part to get the air pocket out, just rev the engine a whole bunch, like up to 5000 rpm. This gets the water pump moving fast enough to push out most pockets of air. Often a clear sign that this has worked is the coolant level in the tank will drop, and there will suddenly be heat coming out of the climate control if there previously wasn't.

Best of luck with the cooling system issues.

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