86 528i help!

E28 technical advice asked and given! Troubleshooting, modifications and more.
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Rabakiller
Posts: 3
Joined: Nov 08, 2020 10:29 PM
Location: Chile

86 528i help!

Post by Rabakiller »

Hello guys. I recently purchased a 1986 528i. I have almost none mechanical knowledge so I apologize if my concepts are wrong. Last week while driving the low coolant warning led turned on and as I stopped the car I realized the engine was boiling. Temp gauge was only 1/4 up (as it was recently repaired I guess the job was not done correctly). Refilled the coolant reservoir and kept on driving. As I opened the trunk I realized that my temp sensors were not as they are supposed to be attached according to realoem manual. Specifically the temp-time switch is attached where the thermovalve should be and there is no thermovalve. Also i noticed that at the same time fuel started to leak just above the rear right wheel (i don´t know if this is related). I would really appreciate any help, thanks!

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Federico
Posts: 371
Joined: Sep 16, 2013 6:38 PM
Location: Argentina / California

Re: 86 528i help!

Post by Federico »

Somebody has been messing around with your sensors. The gauge sensor (the one with the corrugated pipe) should be moved to the back, where you have the plug:

Image

The way it is now, I believe it is measuring the temperature of the cool water coming from the radiator, not the hotter fluid coming out of the block.

The fuel leak seems to be coming from the feed hose between the tank and pump. The other end of that hose can be seen from inside the trunk (lift the carpet and remove the black cover with 3 screws on it. That is, assuming the cover is still there :laugh:
Rabakiller
Posts: 3
Joined: Nov 08, 2020 10:29 PM
Location: Chile

Re: 86 528i help!

Post by Rabakiller »

Thanks!
tn535i
Posts: 5376
Joined: Jul 14, 2006 1:30 PM
Location: Middle Tennessee

Re: 86 528i help!

Post by tn535i »

At least your CTS has been left alone. It's the one that tells the computer the engine temp so that it can run properly. The dash gauge sensor as mentioned being in the wrong place has little to do with how the car runs but should be where it belongs so you can see the true temp.

Also on that t-stat housing is an 8mm screw that is for bleeding air out of the system. In your picture is the frontmost screw coming up that is quite rusty. Loosen that and let air burp out until coolant start to come out then close. Maybe repeat after driving a bit. Also make sure the small hose coming off the top of the radiator on driver's side is free and allowing air and coolant to flow into the expansion tank.

If air continues to accumulate in your cooling system and it overheats you might have a head gasket issue or you could just have that little line clogged or perhaps just a bad expansion tank cap.

Having those fuel lines leak is not uncommon. The one you picture is even accessible by rodents and they like to chew on cars hoses. I had that happen a couple years ago in that same location.
Rabakiller
Posts: 3
Joined: Nov 08, 2020 10:29 PM
Location: Chile

Re: 86 528i help!

Post by Rabakiller »

Thanks a lot!
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