1997 328is Bleeding Coolant Without Heat

[Lewie]

I had my 97 328is with 92k Miles delivered off of Craigslist and I’m running into an overheating issue as I try to bleed the coolant. The car ran alright before replacing the radiator which was damaged from a collision. The heat or ac were not working before replacing the rad. When I try to bleed the coolant with the new radiator the coolant begins to smoke and the engine over heats with the cap open causing the need to kill the engine. Do I need to diagnose the heating issue first in order to properly disperse the heat while bleeding? Is it mandatory to have the heat on for this? I’d like to get the car running again before diagnosing the heater control valve or heater core or whatever else might be the problem. This is my first time doing any real engine repair so thanks for the help!

[mnguyen84]

it shouldn't take that long to bleed the system as it is a closed loop system. Are you bleeding the system with the bleeder screw? If the heater isn't working then it might be the case that you don't have enough coolant circulating your system. Assuming that you're bleeding the system correctly, you might have a blown headgasket if bubbles are coming out non-stop.

I would check the oil for coolant before proceeding.

If all is well, then I would pull the thermostat and see if the car can run without overheating issues.

[Nanniepoo]

Are you bleeding it correctly? Put the front on ramps and fill the system cold as completely as you can. Then start it and keep topping it up as the coolant level drops. Turn heater on full (fan can be on low if though).

[66 6]

As Nannie said. Put the front of the car on ramps, hill etc. Remove the overflow cap. Start the car and turn on the heat to full hot and full fan. Have someone rev the car from idle to 2K back and forth while you watch the overflow tank Keep adding coolant until the level is correct. If your system is working the reving of the engine will pull the coolant into the engine and force the air to the coolant tank. Your interior heat will also become hot.

This is not exactly how people say to bleed the system but this is what works. I've fixed several "overheating" cars with this method even one that just came from an engine transplant at reputable shops which said that the owner needed a new head gasket or head for $$$$.

After you get it all buttoned up and running, then you can use the bleed screw to remove any residual air from the system.

[scooper]

pressure test system first to find leaks then bleed. Bleeding does take awhile contrary to what one poster said. The engine needs to get up to operating temps and heat needs to be on full blast. In the winter outside it took me 45 minutes to bleed.

[XnWarden]

The smoke coming out is the air escaping your cooling system in the form of steam. That is normal. The car overheating while bleeding is also normal. The air holds more heat than the water. So it will run hot until all of the air is bled out.

No need for ramps. They can help, but the fastest way to bleed is to actually fill the system as close to capacity as possible.

When the system is empty, it holds about 11 liters. So you can measure it out and just keep adding it. I ignore the cold line and just keep filling the tank to the brim. The weight of the fluid will cause the level to drop as it flows into the rest of the system. I dont advise you do this. Because you arent familiar with these cars and might overfill it.

A good tip for checking how bled your system is, is to squeeze the upper and lower radiator hoses with the radiator cap off. This will force the coolant thru the bleed port on the top of the tank. If you see coolant coming thru, its close to done. If you just hear air coming thru but dont see a stream of liquid, you gotta add a lot more coolant.

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[XnWarden]

Also, your heat doesnt work if your system isnt bled. So keep the heat on max with the recirculate air button on for the entire bleed process. When you start getting hot air you are close to done.

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[Nanniepoo]

The smoke coming out is the air escaping your cooling system in the form of steam. That is normal. The car overheating while bleeding is also normal. The air holds more heat than the water. So it will run hot until all of the air is bled out. No need for ramps. They can help, but the fastest way to bleed is to actually fill the system as close to capacity as possible. When the system is empty, it holds about 11 liters. So you can measure it out and just keep adding it. I ignore the cold line and just keep filling the tank to the brim. The weight of the fluid will cause the level to drop as it flows into the rest of the system. I dont advise you do this. Because you arent familiar with these cars and might overfill it. A good tip for checking how bled your system is, is to squeeze the upper and lower radiator hoses with the radiator cap off. This will force the coolant thru the bleed port on the top of the tank. If you see coolant coming thru, its close to done. If you just hear air coming thru but dont see a stream of liquid, you gotta add a lot more coolant. Sent from my VS987 using Tapatalk

Wat.

I've never overheated an engine while bleeding. That's the point of filling to capacity while still cold. There will be enough coolant in it to prevent overheating and you just need to work the bubbles out. If you have bleed screw out and you're filling with coolant you can hear the air whistling out of the tiny bleed screw as the coolant displaces it.

Ramps may not be necessary, but 90% of the time when you're doing cooling system work the front is already elevated so you can drain.

I also ignore cold line while filling. Fill it to the brim, once needle has been chilling around halfway for a while, heat is really hot, and coolant level has stopped dropping, I just close it up and turn off the engine. Come out the next morning and top off if needed, and then I'm usually good to go. Might need one more top up after it's first time getting nice and hot from driving.

Concur about stream of liquid.

[XnWarden]

Wat.

I've never overheated an engine while bleeding. That's the point of filling to capacity while still cold. There will be enough coolant in it to prevent overheating and you just need to work the bubbles out.

Concur about stream of liquid.

When I first started working on my car, i wasn't smart enough to fill to capacity. I was worried about the tank over flowing. So i would add to the cold line and turn it on so the level would drop. It took a Very long time to bleed my car because I was waiting for it to reach temp, draw the coolant thru, and then cool down so i could add more.

It sounded like this is what OP was doing, and it was running hot because he let it stay on too long with low coolant. I also made that mistake once. I later figured out you just slowly add about 10 liters of fluid and then start bleeding.

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[Eric93se]

The car was in an accident where the cooling system was damaged, the first thing you should have done is a compression test to make sure the PO did not overheat the engine. If you unaware with these cars the head can warp and crack.

[jmo69]

Read flyfishvt's DIY on bleeding. I've had good luck filling my system through the upper radiator hose and always put the car on ramps. You can get the system nearly full that way. Then I run it, rev it and squeeze the hoses to push any trapped air out.

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[Lewie]

When I first started working on my car, i wasn't smart enough to fill to capacity. I was worried about the tank over flowing. So i would add to the cold line and turn it on so the level would drop. It took a Very long time to bleed my car because I was waiting for it to reach temp, draw the coolant thru, and then cool down so i could add more.

It sounded like this is what OP was doing, and it was running hot because he let it stay on too long with low coolant. I also made that mistake once. I later figured out you just slowly add about 10 liters of fluid and then start bleeding.

Right on the money. Had no where near enough coolant in the reservoir.
Engine is no longer overheating and I’m getting heat now!
I get solid streams in the reservoir when I squeeze the radiator hoses. I’ve let it run and revived it up to 2500 with the the bleeder open and the cap closed and vise versa multiple times. No more bubbles from the bleed and it’s sitting right in the middle on the temp gauge.


Thanks for all the replies guys.