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Discussion Starter · #1 · (Edited)
Hi guys,

After having completed a cooling system overhaul, the fuse #3 in the A8680 fuse box in the engine compartment (close to the DME) keeps on blowing (3 times now).

I still have a coolant leak but it is dark tonight I will have to check more thoroughly tomorrow. I think it is the drain valve under the exp tank that is getting old.

Anyhow, I don't understand why on earth this would cause that fuse to blow. Any idea? I went on the WDS to check what system that fuse is related to (fuel pump obviously) but I don't know what version of the DME I have (car was produced in July of 1998).

So just for your info, here is what I did to the car last week:
  • new lower hose
  • new upper hose
  • new temp sensor
  • new water pump
  • new thermostat
  • new exp tank with new cap
  • removed and cleaned DISA
  • removed and cleaned ICV
  • new lower intake boot
  • new upper intake boot

Tonight, after having bled and refilled the system properly, I went for a ride, about 50km (30miles). First half was cruising along the river at 75km/h and second half highway back home at 120km/h. I kept checking the temperature, steady 95°C, no problem. I decided to push the 2nd gear about 1 mile away from home (5000+ rpm), and the fuse blew. I replaced it, noticed the coolant leak again, and went back home slowly.

Last time the fuse blew, 2 codes got thrown:
P1453 Secondary Air Injection Pump Relay Control Circuit Electrical
P1470 Leakage Diagnostic Pump Control Circuit Electrical
They are not back yet, but maybe pending.

Any help will be much appreciated... :(
 

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Discussion Starter · #2 · (Edited)
Oh and I should also mention that my car has had no electrical current for a long period, and this would have reset the DME adaptation values according to the TIS. Not sure it is useful but anyways...
 

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Just found this thread. It's really hard to say why that fuse keeps blowing, but you have a coolant leak and coolant doesn't play nice with electronics. That would explain the electrical failure codes. My suggestion is that you find and fix that coolant leak first.
 

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Discussion Starter · #6 ·
yep I will definitely fix that tomorrow. But the leak seems to be coming from the mounting plate (item #1 on following diagram), either at the drain plug, the hose that goes to the engine, or the connection to the exp tank. I don't see how it could splash of any sensitive plug.
I also rechecked all the plugs I played with last week, ICV, DISA, AMF and thermostat. Could it be the coolant level sensor electrical connection?
 

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I doubt the level sensor would be causing that problem. They typically register open or shorted anyway.

What I'm wondering is if you've got leaks in other areas that could cause problems.
 

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Unplug the thermopstat see if it stop blowing. Sounds like you got a cheap thermostat
 

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Discussion Starter · #9 ·
I checked thoroughly around the water pump and the thermostat, and didn't see anything abnormal
 

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Discussion Starter · #10 · (Edited)
Unplug the thermopstat see if it stop blowing. Sounds like you got a cheap thermostat
yep, I wanted an original one but I ordered the whole kit including this MTC aluminum housing thermostat.

EDIT: is it safe to unplug the thermostat? won't I overheat? I don't mind if it throws a code... as long as I know I'm safe. I've closely monitored it's activities when I took my 30 miles ride and the coolant temp never went above 96°C
 

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yep, I wanted an original one but I ordered the whole kit including this MTC aluminum housing thermostat.

EDIT: is it safe to unplug the thermostat? won't I overheat? I don't mind if it throws a code... as long as I know I'm safe. I've closely monitored it's activities when I took my 30 miles ride and the coolant temp never went above 96°C
Computer open the thermostat under certain conditons. The thermostat is still mechanicly opened under MOST conditions. You can drive it around with it unplugged for a little while for testing. Was I correct? Did unplugging it stop the fuse from blowing???
 

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Discussion Starter · #12 ·
I removed the expansion tank today. The leak was coming from the connection between the tank and its mounting plate. I took the mounting plate out and forced the tank on it, making sure it would be tight. Filled and bled the system, and drove away. Temperature is good, no leak. The fuse didn't blow again yet. I'll try pushing the rpm a bit more tonight. Didn't try disconnecting the thermostat yet. If the fuse blows again I'll try.

Thanks a lot for your help guys.

Sent from my SAMSUNG-SGH-I896 using Bimmer App
 

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Discussion Starter · #13 ·
Computer open the thermostat under certain conditons. The thermostat is still mechanicly opened under MOST conditions. You can drive it around with it unplugged for a little while for testing. Was I correct? Did unplugging it stop the fuse from blowing???
:clap:

jbeurotech you were right!
I didn't have much time until today. Unplugged the TStat, went for a ride (closely monitoring the coolant temp). When I reached normal temperature (95°C) I did a couple of WOT/redline runs.
No problem whatsoever. Temperature stayed dead between 95-96 and everything was fine.
I carefully checked the TStat and saw a little mount of coolant on it. There must be a small leak there, but it doesn't seem to be coming from the gasket :hmm:
Anyway... This cheap MTC aluminum thermostat was what I was worrying the most about, I guess I'll have to talk to ECS should it be defective out of the box.
 

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:clap:

jbeurotech you were right!
I didn't have much time until today. Unplugged the TStat, went for a ride (closely monitoring the coolant temp). When I reached normal temperature (95°C) I did a couple of WOT/redline runs.
No problem whatsoever. Temperature stayed dead between 95-96 and everything was fine.
I carefully checked the TStat and saw a little mount of coolant on it. There must be a small leak there, but it doesn't seem to be coming from the gasket :hmm:
Anyway... This cheap MTC aluminum thermostat was what I was worrying the most about, I guess I'll have to talk to ECS should it be defective out of the box.
Yup crappy parts will get you everytime!
 
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