Project 33: Coolant Replacement

[Wayne 962]

Got any questions on Project 33 for your E36 or E30? Ask them here!

-Wayne

[withnail]

Preparing to undertake this project - where can I get the aluminum sealing ring that is mentioned in the technical article and in the book? It says this should be replaced at coolant change.

Thanks!

[Yurick]

I believe that this is the ring that goes onto the radiator drain bolt. If it is not available standalone, then it should come with the new drain bolt.
Hope this helps.

[withnail]

I'll just have to check and see if the radiator drain plug and engine block drain plug include the respective o-rings or sealing rings... Thanks.

Another question I had about this undertaking is flushing the system after draining it. I see a tech article on the Pelican site describing how to do just that. Does the miniscule amount of non-distilled water left in the system after flushing with a hose as described have any negative effects?

[Yurick]

Probably, but then again, it won't kill it.

[eureka]

First off, thanks Wayne for documenting and sharing a very important project.

The project states that you should

Place the heater control knobs all the way on hot, turn the ignition to the on position, and turn on the passenger compartment fans to their lowest setting. Do not start the car.

When do we turn the ignition to the "off" position (and thereby switch off the fans and the heater)? Is it:

a. after draining the engine block?
b. after bleeding?

Thanks!

[Jeron]

The intent is to have the heater valves open while the cooling system is draining so that the heater core is drain as well. Once you are done draining you can turn the key top to OFF.

Once you get everything opened up you could do the ON and full heat for just 10-20 seconds and all the coolant out of the heater core. If it is just dripping at that point you may even hear the coolant draining into the pan.

[eureka]

Thanks for the quick response, Jeron.

There's only one last thing that bugs me because I'm planning to do this with the engine cold.

When I refill the system through the expansion tank, how does the coolant get into the engine block if the thermostat is closed? How does it get into the heater core if the heater is off?

Thanks again!

[Jeron]

THE most critical step is bleeding the air from the system. I've posted the procedure many many times. I'll probably have to amend this because I've only got minute but here's what I do.

1) fill the expansion tank
2) fill the engine through the top hose
3) fill the radiator
4) button up the system but leave the expansion tank open
5) open the bleed valve
5) Start
6) heater on hot
7) rev the engine to 2k for 5 sec
8) add coolant
9) keep repeating 7 and 8 until the engine is hot
10) about now you will need to close the reservoir but leave the bleed screw open
11) rev the engine with bleed screw open and hopefully by now the heater is hot
12) close the bleed screw
13) Drive it but carry some coolant with you
14) drive normally for a few days but each evening do 11 and 12

I'll try to reread all tomorrow

[eureka]

Hi Jeron,

I appreciate your posting the bleed procedure but I will not be going that route because I have the Blue-Point RADKITPLUS which, in theory, should refill the system without any air bubbles.

After I did some reading here, I can answer my own question: the thermostat is located where the coolant mix leaves the engine to go to the upper radiator hose. The lower radiator hose is the path where fluid enters the engine c/o the water pump.

[Jeron]

I hope that works for you. I'm skeptical. The E36 is notoriously hard to bleed.

[Buckeye325is]

On my M20 engine it has coolant hoses running to and from the Throttle. What purpose does this serve??

Additionally, the one going from the bottom of the thermostat housing was completely plugged off with crud, but the car seemed to run fine. Since I've now cleaned it out will my car perform better?? How much horsepower will having coolant go to my throttle add?? I'm hoping at least 10-15 .

Thanks

[Jeron]

Lots of web speculation on TB coolant lines. The lines are there to keep the TB warm, obviously. The impact on performance is negligible so don't expect any gains from plugging them.

You said the line coming off the bottom of your thermostat housing was plugged. that line appears to go to the TB. I wonder if a previous owner didn't cap the line or plug it intentionally and you simply discovered that sludge has been collecting there over time as a result.

[Buckeye325is]

The hoses weren't capped off ever, the prev. and only driver/owner was a 50-60y.o. nurse in Florida who must have run almost straight tap water in the system. I've never seen such bad mineral deposits, the water pump impeller was almost rusted solid. The outlet "L" on the thermostat housing was corroded almost solid and looking at the TB side it appears to be the same. All aluminum fittings are corroded and pitted.

I discovered this while doing the timing/water pump change this week. The car hadn't been started for the past 6 years, but had been garaged; and supposedly only virginal BMW certified mechanics with white gloves were allowed to touch it.
They just never put antifreeze in it.

I plan on doing a complete system flush, but I wonder how bad the heater core is corroded as with other things. It's run fine for the past 4-5months since I bought it, I'm amazed.

I still think with getting out all the mineral deposits I should pick up at least 25-30hp.

[Yurick]

I hope you do, but don't hold your breath...

[bmachine]

Jeron,

I purchased the book and did the full water pump / tstat / hoses / belts replacement this weekend. Although everything went well, I am now realizing what you mentioned earlier which is that the bleeding is the trickiest part. The book goes over it very lightly and the forums are full of "Here is what I do" and "Here is what Bob does", none of which really explains how this strange e36 bleeding system works.

After having filled the system with the bleed screw open and engine cold, I realized that if I then ran the car around town for a bit, coolant would leak past the reservoir cap. As if pressure from a hot engine made the coolant bubble out. After the engine cooled down, I opened the bleed screw and heard a good deal of air coming out. But curiously, as the air came out, the coolant level in the reservoir went up dramatically, almost to the top of the reservoir. This is very strange because I would think that if I let the air out of the system that would get replaced by coolant and, if anything, the coolant level should drop and not increase ... What is going on there?

I have noticed that you recommend doing the bleeding with the engine hot. I will have to try that tonight.

Thank you for any help,

Bo

[bmachine]

I should probably add that this is for a 94 325is.

[eureka]

Hi all, just to update everyone. The part number for aluminum crush washer for the engine block coolant drain plug is 07-11-9-963-200 and costs only $0.50 from PelicanParts

[bmaurer]

I too have replaced the pump, tstat, big hoses and belts and bled the system per Bentley. But I have no heat and after exhaustive reading of blogs was afraid I did not bleed the system enough. Is the cooling system with the attached expansion tank not capable of purging air during hot/cold cycles like every other car for the last 20 years?

[Jeron]

Apparently it isn't capable. Sooo many problems reported. I think it is the loop that runs to the TBody is too high, the highest point in the system. I bypassed mine and had no problems bleeding last time.