Draining Coolant

[BMW86]

Anyone know how to drain the coolant on an N54? I know how to top it up, but I checked my fluid and it looks nasty (brown and thick) so I want to flush it out completely. I read somewhere that you need to drop the FMIC to get to the plug. Any tips would be great.

[Pig Farmer]

On the US model, you can pull the lower hose on the passenger side of the car. The hose has a clip similar to those that connect the intercooler. Just pull the clip to unlock and wiggle the hose free. Two other comments... First, there is a process to prime the water pump after filling the system with coolant. Turn the car's heater to full hot, turn the fan to the lowest setting, turn the car's electrical system on without starting the car, and hold the gas peddle to the floor. You will hear the water pump cycle on and off for several minutes until the pump is primed. The other comment deals with the color of your coolant. Brown and thick may suggest you have oil in your coolant. Sometimes oil in the coolant takes on the appearance of chocolate milk. If you drain the coolant and find oil, and you are not seeing a bunch of white smoke from the exhaust, it is likely the seal between the oil filer housing and the block. Hope this is not the case. Good luck with the drain.

[BMW86]

Originally Posted by Pig Farmer

On the US model, you can pull the lower hose on the passenger side of the car. The hose has a clip similar to those that connect the intercooler. Just pull the clip to unlock and wiggle the hose free. Two other comments... First, there is a process to prime the water pump after filling the system with coolant. Turn the car's heater to full hot, turn the fan to the lowest setting, turn the car's electrical system on without starting the car, and hold the gas peddle to the floor. You will hear the water pump cycle on and off for several minutes until the pump is primed. The other comment deals with the color of your coolant. Brown and thick may suggest you have oil in your coolant. Sometimes oil in the coolant takes on the appearance of chocolate milk. If you drain the coolant and find oil, and you are not seeing a bunch of white smoke from the exhaust, it is likely the seal between the oil filer housing and the block. Hope this is not the case. Good luck with the drain.

Thanks for the detailed response. I really appreciate it. The oil definitely has the appearance of chocolate milk, no white smoke either. What's involved with the seal between the oil filter housing and the block?

I will aim to drain it asap and report back.

[Pig Farmer]

I believe the oil filter housing is held on with three or four bolts, but one is blocked by the intake manifold so you may need to remove the manifold. I haven't done this repair myself but there are several posts that describe what is involved. Just do a search for "oil filter housing" or "oil in coolant".

[BMW86]

Originally Posted by Pig Farmer

I believe the oil filter housing is held on with three or four bolts, but one is blocked by the intake manifold so you may need to remove the manifold. I haven't done this repair myself but there are several posts that describe what is involved. Just do a search for "oil filter housing" or "oil in coolant".

Do you think replacing the oil filter housing will resolve the issue? I have an aftermarket oil cooler with stock thermostat delete and recently had a leak from the backing plate. Do you think it's related?

[Pig Farmer]

I believe you only need to replace the gasket between the block and the oil filter housing... Not the whole housing. This is different than the o-rings used where the oil cooler bracket/lines plugs into the oil filter housing. I'll see if I can find the DIY that I saw a couple months ago.

[BMW86]

Originally Posted by Pig Farmer

I believe you only need to replace the gasket between the block and the oil filter housing... Not the whole housing. This is different than the o-rings used where the oil cooler bracket/lines plugs into the oil filter housing. I'll see if I can find the DIY that I saw a couple months ago.

Thanks for the tips. I just drained the coolant from the heat exchanger. Filled up with coolant and followed the procedures. Went for a short drive and seems fine, for now. Still oil in the coolant though, I think this will come out with a few flushes.

One of the 3 bolts that holds my thermostat delete plate to the oil filter housing has eaten the threading in the oil filter housing. I've since blocked it off properly with a different screw and nut. Since you're saying I need to replace the gasket between the oil filter housing and the block it looks like I need to remove the intake manifolds to get the oil filter housing out. May as well change the oil filter housing while I'm in there due to the threading issue. Looks like it's a pretty big job but needs to be done.

[Pig Farmer]

Okay found it... Search for the thread titled "oil in radiator". Post #11 from Dackel has a link to E90Post that shows pictures of the DIY. As the member suggests, since you have the manifold removed, it may be a good time to clean the intake valves. Someone else suggested running a bit of dish detergent in the coolant to get the oil residue out of the radiator, then flush a couple times to get the soap out. Good luck. Keep us posted on your progress.