Need help with heating and cooling system for M54b25 e39

[jaredmac11]

2001 525i M54B25

My heat wasn't working yesterday. It was the first cold day of winter here and the first time I put on the heat.

After my drive I noticed half of the vent was hot the other was cold. I assumed there was air in the system so I started to bleed it. Full disclosure the bleed screw broke so I used a bolt with the same thread pitch.

I don't know what I'm doing wrong but all I know is the car will not bleed. In fact it got worse. It never overheat before but when I took it out of the driveway to test my bleed job, it started overheating.
Now I can't seem to bleed the system at all. I feel like the thermostat (replaced last year) is stuck closed bc the car over heats so fast. Sometimes when I put more coolant in, it will burp but the coolant reservoir fills up fast.

Note I never had overheating issues until now. So stupid question but how do I start over from here? Can I leave the reservoir cap open or is that introducing air in to the system? Is there something else besides the thermostat that regulates coolant to the Heater core that could be abrupting full coolant flow while the heat is on?

[mattmar1]

are you bleeding the cooling system with the car hot(or running) or off and cool? aux water pump can adversely affect both bleeding and heater function.

[edjack]

You don't mention any recent cooling system repairs.

Do you have any leaks?

Bleed Cooling System BMW method

On your I6, you need to raise the front end of the car up as high as you can to get the air to the front of the engine.

*********************************

Cooling system bleed procedure (E39)

- with cold car
- top up coolant to proper level (even slightly higher will not hurt at this stage)
- leave rad cap loose

This stage bleeds air trapped in the heater system.
- turn on ignition switch to position 2 (no start)
- set temperature selectors on the climate control to max temp.
- manually set the fan speed to low (lower end of speed range)
- start engine (check that climate settings have not changed)
- after 5-10 seconds of running rev the engine 3-4 times to about 2500 RPM - hold there for about 5 seconds each time.
- shut off engine (should not run for much longer than about 30 seconds - you just want to shut if off before it starts to generate any heat and expand the coolant).
- inspect the coolant level and top up again if necessary.
- tighten the coolant fil cap.

This stage bleeds air from the engine, rad and fill tank.
- now warm up the engine (drive a bit if you wish)
- with engine running CAREFULLY / SLOWLY open the bleed screw. Hold a rag around the area to prevent any excess splashing. Keep the screwdriver in the slot of the bleed screw so you can close it quickly.
- you should have some air/steam escape - progressing to some bubbles of coolant.
- as soon as it progresses to the stage where you are seeing liquid coolant come out then close the bleed screw. Do not over tighten - it is all plastic threads and you can easily turn too far at which point the screw jumps back a thread and you have to re-tighten. Just make it snug with all coolant stopped.
- when the car is cold again re-check the coolant level and top up again if necessary.

NOTE - some of the 6 cyl models have 2 bleed screws - the second one is near the thermostat. In that case you should bleed at both locations (one at a time)

You may have to repeat the bleed procedure 1 or 2 more times over the next week. Can "probably" skip the stage for the cold start bleeding of the heater system.

If the level continues to fall below the correct level then have the system fully pressure tested - explaining to your service manager what you have already done.

It is very important that all leaks be sealed so that the system can operate at full pressure. The engine computer is programmed to keep the coolant temp at about 108C at "most" times (there are exceptions) and the only way it can maintain that temp is if the pressure can be maintained - system fully sealed.

Cheers
Jim Cash

[geargrinder]

Bruv maybe try not to start 2 threads on the same problem.

https://www.bimmerforums.com/forum/s...ing-E39-M54b25

As said in the other thread - the left/right are 2 heater cores with 2 valves so if one side isn't working 99% chance the valve is the issue.

The overheating is indeed a different question I'll grant you that.

For whatever reason the I6 seems trickier to bleed than the V8 which really gives me few problems... but Ed has listed a soup-to-nuts bleed procedure above (the whole thing is overkill IMO in most cases but if you have a problem situation you do probably want to dot the i's etc...)

[BimmerBreaker]

That bleed procedure is unnecesarily complicated imo

Open expansion tank cap and open bleed screw
Pour in coolant until it comes out of the bleed screw
Close expansion tank cap and tighten bleed screw fully
Blower speed lowest, hvac temps at max
Start car, crack expansion tank bleeder periodically until car is at operating temp
A few revs helps as well, crack the bleeder right after revving
Once only liquid comes out after checking a couple times, the bleed is done. Let cool and top up the next morning

Theres no magic to it, but if the car has a coolant leak it wont bleed properly. Use a pressure tester to test the condition of the cooling system. Maybe HVAC valve or a hose is leaking which could cause all these symptoms.

[Jason5driver]

I have been complaining about no heat in my car for weeks now.
I came to found out that the car was running on low coolant.
There was a slow coolant leak coming from the 2 plastic coolant pipes under the intake manifold.
I had forgotten about replacing those pipes when working on the cooling system many years ago.
Last week the pipes finally gave out and and I was left stranded, luckily 1 block away from my mechanic’s shop.
I am removing the intake manifold right now in order to replace the bad coolant pipes.
The CCV under the manifold was so brittle that it cracked to pieces when trying to remove it.
None of the cheap plastic quick connect hose connection released in order to remove the hoses.
Plastic garbage !

When bleeding or adding coolant, you add coolant when the key is in position 1, without the car running.
Heat on max temp on low fan speed.
The secondary water pump will run and circulate the coolant through the system while adding coolant, until it starts to spill out from the bleed screws.