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BMW E28 535i overheating

E28 technical advice asked and given! Troubleshooting, modifications and more.
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pablokinney
Posts: 1
Joined: Feb 04, 2025 10:14 PM
Location: United States

BMW E28 535i overheating

Post by pablokinney »

Hello,
I have a 86 535i e28 BMW and it has been overheating like crazy, I started off with replacing the thermostat, then replaced the fan clutch, then replaced water pump, then replaced thermostat and housing this time, still overheating, replaced radiator, replaced dashboard cluster and the IS board as well. Also replaced both temp sensors on the side of the radiator as well. It overheats whether I am at idle or driving down the road or highway. I have also replaced and bled the system three times and so now I am just plain frustrated! 
Any advice is appreciated!
Mike W.
Posts: 27275
Joined: Feb 12, 2006 12:00 PM
Location: California Whine Country

Re: BMW E28 535i overheating

Post by Mike W. »

Welcome to the group pablokinney!

There's a couple of things that come to mind, cross your fingers and hope on the first one. Hope it still isn't bled right. My test to see if it's bled is does the heater work? If the heater works, it's bled. If it doesn't work, it's not bled.

The second one is a blown head gasket. Possibly with a cracked head to go along with it. Early M30s were pretty marginal on both cooling capacity and the robustness of the head. By the time E28 535s got here they were pretty good, but it's still a long aluminum casting that can and will warp if it's gotten too hot. Quick check is to open up the coolant tank, when it's cool to cold of course, you don't want to be wearing 220F+ water/coolant, but take the radiator cap off and start it up. Then look in the tank. You should not see bubbles. You will always see turbulence as coolant is always coming in from that little 8MM hose coming from the radiator, but not bubbles. You've got to look closely, but there's a difference. Bubbles mean combustion gasses are getting into the coolant, which they should not be. Now you might want to check it, there are kits at either Amazon and elsewhere, or the local auto parts store that will detect combustion gasses, better to double check than do way extra work, but it sure sounds like a blown HG from here. No experience with any of them, https://www.amazon.com/s?k=head+gasket+ ... anker_2_20

A couple more things, make sure the hose from the radiator to the coolant tank isn't blocked, if it is you won't be able to bleed it properly. And remove the oil filler cap, if you see a bunch of white junk on it, "mayo" that's a read bad sign. Occasionally in winter depending on the climate it can accumulate without a major problem, but not usually. And pull the dipstick, it should like like motor oil light brown and semi clear if it's just been changed, or even if it's black and dirty. But it should not look like chocolate milk, that means coolant is mixed in there with the oil.
Chicagotrader92
Posts: 80
Joined: May 11, 2023 11:35 PM
Location: Chicago

Re: BMW E28 535i overheating

Post by Chicagotrader92 »

Isnt the coolant temp sender on the thermostat housing, not the radiator? Wonder if it really is overheating here... Double check the drive belts for anything obvious. 
Chimi-Changa
Posts: 1665
Joined: Nov 08, 2011 11:02 PM
Location: Massachusetts

Re: BMW E28 535i overheating

Post by Chimi-Changa »

M30's are not easy to get all the air out. How are you bleeding? I raise the drivers front corner of the car slightly, attach a hose to the expansion tank nipple and blow slow and steady in the new hose while holding the original expansion tank end straight up in the air from the radiator corner. You should hear air coming out, maybe bubbles and eventually coolant. I usually do that a couple/few times and hopefully is good to go.
Foonfer
Posts: 747
Joined: Mar 18, 2015 11:33 PM
Location: New York, NY

Re: BMW E28 535i overheating

Post by Foonfer »

when you say "overheating like crazy" what do you mean, where does the needle go, does it go 2/3rds, 3/4ths, or does it go all the way to the red?

Mine tends to stay between "just past the middle" and 2/3rds (needle still covers a bit of the thermometer symbol), and I'd like to see it sit dead in the middle...
1st 5er
Posts: 21874
Joined: Jun 13, 2008 12:15 AM
Location: Cypress
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Re: BMW E28 535i overheating

Post by 1st 5er »

Welcome. 

Any progress?
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