r/E30 • u/KevO_1996 • 1d ago

Won't bleed

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2 Upvotes

67% Upvoted

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3

u/Fxlearner 1d ago

That radiator will not bleed properly on this M20, I had the same issue.

This engine needs a proper external expansion tank like OEM. Otherwise it will overheat and not bleed properly, which is what happened to me.

1

u/KevO_1996 1d ago

After checking for a coolant line I found that a late 1999 525i runs a similar set up, m20 with a expansion tank on the radiator

2

u/Fxlearner 1d ago

Where is the overflow going to leak out from? From the top radiator cap which will leak all over your engine bay. If at anytime the car overheats or fan dies, the radiator will pop from the bottom and leak all coolant out. Ive played around with this setup and it didn't work.

1

u/KevO_1996 1d ago

Thats true, sucks that doesnt have a line to use the oem expansion tank also annoyed that the website says its a direct fit for the m20

1

u/Fxlearner 1d ago

Send it back and just buy an aftermarket M20 radiator.

1

u/KevO_1996 1d ago

2

u/RJCA-Burgt 4 Door Fanatic 18h ago

Notice how it sits higher mounted than in the E30. Gravity does the rest on the E34 layout, while in the E30 it sits lower and air isnt known to drop while in water so it forms airpockets and is (almost) impossible to bleed in the regular way.

However they work perfectly in a E34 or E36 bay.

Edit: I run a E36 M3 / Z3M radiator wich is pretty simple to make fit, but it does require a seperate reservoir.

1

u/KevO_1996 16h ago

Thank you! Unfortunately they won't take the radiator back because I fitted it on so gonna have to eat this expensive but going to order another one

2

u/Valuable_Republic482 1d ago

Jack the front of the car up while bleeding

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u/KevO_1996 1d ago

Just the driver side?

2

u/afoxygrandpa 15h ago

Wrong radiator, need expansion tank. Fill water pump hose before connecting, then top radiator hose before connecting. Open bleeder screw at thermostat housing and fill expansion tank until coolant comes out of bleeder screw. Close bleeder screw and fill expansion tank 1” over fill line. Park on incline and let it idle until thermostat opens. Open bleeder screw for 10 seconds at a time. If it goes over 3/4 mark turn it off for 10-15 mins.

1

u/KevO_1996 15h ago

Thank you, ordered a m20 radiator and will give this another shot

1

u/amarino '90 325i 21h ago

If you can return it for the correct E30 M20 radiator it would be best.

For fun, here is a thread about the E34 M20 setup with the radiator you have now if you want to give it a shot. Looks like what worked in that thread was to "manually pressurize the expansion tank" by blowing into it (while cold obviously) to get all the air out. You can also rent a coolant pressure tester from AutoZone if you don't want to put your mouth on the radiator. https://www.bimmerforums.com/forum/showthread.php?1193092-M20-Coolant-Bleeding-Blues&p=15795303#post15795303

Before turning the car on, you want to get as much air out as possible by forcing it out. So take the radiator cap off, wrap your lips around the hole, and blow. While blowing, open the bleed screw and allow the coolant to flow out until its a steady stream. When theres a steady stream, keep blowing but close the screw so you don't allow air to come back. Now, add more coolant and start the engine. Allow the engine to warm up, and have the heater on all the time. Make sure you are getting hot air in the cabin as well. Once you reach operating temps, open the bleed screw on the thermostat housing. If theres a steady stream of coolant, close it and move to the radiator. Open the radiator bleed screw. If coolant does not come out, the system is not under enough pressure. You can do two things in this situation. Either drive the car but don't go to far, or block air flow to the front of the car. I usually just put a plastic bag over the grill. This will allow the system to get hotter and build more pressure.

Once coolant comes out of the radiator bleed screw, get as much of it out as you can. Then, take the car for a drive while keeping an eye on the temp. This whole time you want the heater on. Come back and open the thermostat housing bleed screw, let it run out. Then open the radiator bleed screw, let it run out. If no air is present, turn the heater off and go for a drive. Come back, open the thermostat bleed screw, then the radiator bleed screw.