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2002 325xi
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You know, dealing with refreshing the coolant system myself these past couple of weeks, do you have the automatic? Have you replaced the thermostat for the trans cooler that’s in the bottom of the coolant reservoir? That’ll certainly give you grief even if you DO bleed it perfect. It was certainly giving me problems.
 

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Let me rephrase. The yellow cooling light did come on and off before the temp gauge displayed it overheating.
That yellow light is called Low Coolant Level light.
Re to temperature gauge, how far from center did it move when you saw it was overheated?

Important question: how exactly did you bleed the system, in detail every step?
 

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2000 323Ci coupe manual
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I think you are TOO smart for this car. I would sell it and get something more inline with your abilities like a corolla or civic.
 

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2001 325i Sedan
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My thoughts exactly. Sensors can go bad. Tossing parts at the car is no substitute for a proper diagnosis.
Unfortunately, the OP seems rather uninterested in answering many key questions, which makes it near impossible for any of us to make many useful suggestions. And, he clearly does not understand how the whole system works, and what the idiots lights actually mean. But, not losing coolant == NOT actually over-heating.
 

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Discussion Starter · #25 ·
Unfortunately, the OP seems rather uninterested in answering many key questions, which makes it near impossible for any of us to make many useful suggestions. And, he clearly does not understand how the whole system works, and what the idiots lights actually mean. But, not losing coolant == NOT actually over-heating.
What key questions have I not answered? I stated everything in length about what I’ve done to the car. Maybe you should read over it again. Also you do understand not losing coolant can still overheat the car correct?
 

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Discussion Starter · #26 ·
That yellow light is called Low Coolant Level light.
Re to temperature gauge, how far from center did it move when you saw it was overheated?

Important question: how exactly did you bleed the system, in detail every step?
It was moved over to the red and sat there for a bit. I’ve dealt with this before on a prior thermostat change where I got the car up to 95mph and it started overheating but as soon as I let off it went back to normal. I added the coolant and had the bleed screw released some then watched it settle and reattached the coolant cap and then tighten the bleed screw after a bit along with the temp at 91 and about mid fan. Engine off
 

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Possibly if your car is displaying a constant low coolant light whilst overheating could mean your losing water somewhere or it could be a broken head or a broken head gasket. My car cooked itself when i was going up a hill and the lower coolant pipe blew off, making it overheat quickly. Its been on death row for a few months but im finally pulling it out now. I really hate the 318i engine because of the secondary air pump. My advice would be to get a rad teaster to see if blown. Also check the oil dipstick for milky liquid or the radiator for the same. Best case scenario it was one of the thermostats or sensors gone wrong...

Good luck
 

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What key questions have I not answered? I stated everything in length about what I’ve done to the car. Maybe you should read over it again. Also you do understand not losing coolant can still overheat the car correct?
Good way to generate interest in your car problems. Perhaps you should read it over again. I'm out.
 

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It was moved over to the red and sat there for a bit. I’ve dealt with this before on a prior thermostat change where I got the car up to 95mph and it started overheating but as soon as I let off it went back to normal. I added the coolant and had the bleed screw released some then watched it settle and reattached the coolant cap and then tighten the bleed screw after a bit along with the temp at 91 and about mid fan. Engine off
That is not anywhere near close to the proper way to bleed the system. I saw a really good video on the proper way but I can’t seem to find it. There are plenty of good how-to’s on here of the proper way.


This is the video I used for bleeding, Otto from Bavarian auto. I followed this method and had zero issues.





Sent from my iPhone using Tapatalk
 

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Discussion Starter · #32 ·
That is not anywhere near close to the proper way to bleed the system. I saw a really good video on the proper way but I can’t seem to find it. There are plenty of good how-to’s on here of the proper way.


This is the video I used for bleeding, Otto from Bavarian auto. I followed this method and had zero issues.





Sent from my iPhone using Tapatalk
Thank you sir. You are a lot of help.
 

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That is not anywhere near close to the proper way to bleed the system. I saw a really good video on the proper way but I can’t seem to find it. There are plenty of good how-to’s on here of the proper way.
This is the video I used for bleeding, Otto from Bavarian auto. I followed this method and had zero issues.

This is a bad method: the tank was over filled and engine should not run up to normal temperature with tank cap not closed.
 

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I added the coolant and had the bleed screw released some then watched it settle and reattached the coolant cap and then tighten the bleed screw after a bit along with the temp at 91 and about mid fan. Engine off
Was the engine off while you doing this, or engine was running? Engine temp at 91C or ambient at 91F? Nobody here can read you mind.
 

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This is a bad method: the tank was over filled and engine should not run up to normal temperature with tank cap not closed.
Once the engine is cool I used a vacuum pump to suck a little out of the expansion tank so it was at the correct level. Other wise I didn’t have any trouble.


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You're focusing on the thermostat and that's 100% not a problem.

You either have not properly bled the system, you have a slow leak, some internal blockage, or you have a sensor problem.

You can check the sensor problem with a code reader and inexpensive IR thermometer. If you're within a few degrees between the code reader and actual engine temp assume it's good.

Next, bleeding. People make this harder than it needs to be. Buy an inexpensive coolant filler funnel like this.

1. Open up the bleeder screw while filling the system to allow air to purge out when filling with coolant, then close the screw.
2. Continue filling coolant until the funnel is about 1/2 full. Start the engine, turn the heater on full hot, fan speed on the lowest setting.
3. Observe the coolant in the funnel and refill as necessary. Watch for air bubbles. Let the car idle until the electric fan comes on.
4. When you see no more bubbles, use the stopper to plug the funnel, and replace the cap.

Take the car for a drive - turn on your Defrost and if there is hot air coming out of the vents, you're almost certainly bled. On BMW's the heater core is the last to get air purged (likely due to a combination of it installed higher in the car and having an electric supply pump)

The next morning, double-check the coolant level. Since water contracts when it cools, it's possible you could be a little under-filled once the system has cooled down. It may need a very small amount to fill it to the "KALT" level on the tank.

If you're still having problems after this process, next step is to pressure test the system and check for leaks (you could do this before you bleed if you want). After that, I would take it to a shop and make sure you don't have a blown head gasket and are slowly consuming coolant.
 

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Not exactly. Because the system has been heating to the air, the coolant has been allowed to expand more than it would if it was heating under the pressure of the system. That's why, believe it or not, once the system cools the level will be close to perfect, if not a little low.

It's easy of course to validate my procedure - but I've found almost every time I need to add a little coolant the next morning.
 

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Discussion Starter · #40 ·
Re above procedure: have you not just left it with the exp tank full to the brim?
That’s what I don’t understand with me bleeding it. I had proper heat and everything. Although I did notice the far right side wasn’t blowing heat but figured that could be something unrelated or not serious. Maybe my car isn’t overheating and it is just a sensor.
 
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