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Discussion Starter #1
:dunno::dunno:I have a 2000 540i. It recently started leaking from the explansion tank. The temp gauge was working fine and showed the increase when the liquid leaked out of the expansion tank.

I replaced the tank and the level sensor. The interior of the tank had many broken parts.

Refilled the fluid and started the car. Car heated up fine.

The next day I drove the car and within one mile the temp gauge pegged. I turned around and returned home. The gauge returned to top dead center and slowly increased and then pegged.

Now when I turn the key the gauge immediately pegs. I can not start the car.

I am not positive but is this the temperature sensor on the water pump or the one on the ratiator hose?

Are these related issues or just a coincidence?

Any Thoughts?

Thanks,
Mitch
 

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I am not positive but is this the temperature sensor on the water pump or the one on the ratiator hose?
Did you open the bleeder when you refilled the system after replacing the expansion tank? You may have an air bubble in there.
 

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If you cant start the car its one of 2 things. Either your coolant temp sensor is not working at all, or the engine is seized from driving it while overheating (I doubt that though). Do a search for cooling overhaul V8. This is a very common issue with e39s, they were made with a crappy cooling system.
 

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Discussion Starter #4
Bleeder was opened

When I first heated it up, I did not open bleeder until it was hot. Not much came out.

I later tried a full bleeding regimen right from Bently. Again nothing really changed. I little air and the level in the expansion tank has remained the same as when I originally filled it.

Could an air bubble cause the gauge to peg?

Thanks,
Mitch
 

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Discussion Starter #5
I should clearify. I actually can start the car on occassion after it sits for some time. It runs a little rough. If I shut it off and then try to restart it just sounds like it is trying but can not catch - almost like a carb problem.

My thought it that the computer is telling it that it is hot and the fuel system is too lean to start cold.

Mitch
 

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Discussion Starter #6
Danny, I agree that a full overhaul is in order. If possible, I would like to replace a temp gauge so that I can drive the car while I get ready with parts and fortitude to perform the overhaul. I am used to equipment as a farmer but this beast is much different for a tractor or crawler.
 

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the thermostat is on the pump easy to change, i just changed mine on my v8 took about 40 mins, part is 80 bucks at the dealer. just watch that bolt in the back, need a 10mm cresent wrench. took me a minute, to get it off, but swaped, then bleed system, and no worries now,
 

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Try replacing the coolant temp sensor and see what happens (all the info should be avail. in that DIY). But if it overheats again dont play with fire, get the car fixed before you warp a head.
 

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Just had the same problem with my grandfather's 540. Replaced the thermostat (not sure if it was ABSOLUTELY necessary but meh…) and reset the computer. The temp gauge gets stickied to the red zone for some reason…

I have a feeling a bad bleed caused my initial problems, and the thermostat caused the temp gauge to get sticky.
 

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Discussion Starter #10
Looking through Bently carefully, it appears that the IKE (intrument cluster module) has a connection to the dual temperature sensor that is on the Thermostat, not the coolant output hose. I will try the coolant output hose to see if it works but I know I have to get at the bigger job.

Would a code reader give me anything useful? I currently do not have one but I am considering one - either the Peak or the AutoEnginuity. The later is somewhat expensive - I am trying to determine if it is worth it.

Thanks all of you!

Mitch:)
 

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Wait a minute!

As mentioned by two others, you problem is most likely the thermostat, NOT your temp gauge or temp sender. It has been told to me by a couple BMW techs that once you overheat the car, the thermostat will usually crap out shortly there after. Sure looks like that is what is happening to you. I would not drive the car until this is resolved.
 

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If you have gotten all of the air out of it, the car would not be overheating. If the temp is climbing rapidly to an overheat from a cold start you do not have enough coolant in the engine, and/or there is a giant bubble of air in it. The m62 is not known for being too difficult to bleed.

once you are 100% sure it is not a trapped air issue, I would suspect a failed thermostat as mentioned above, or possibly a water pump that had the impeller come off the shaft inside the block.
 
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