BMW E36 1998 316i - Coolant Flush

Honest John Back Room » Technical matters
View Threaded
Wed 18 Oct 2023 21:26
BMW E36 1998 316i - Coolant Flush - Jordan Crockett

Evening,

I picked up an old e36 to get me around and learn how to maintain cars myself. My thermostat is sticking open on the motorway and the engine temp is dropping on longer journeys so I'm looking at replacing it.

I've always been a bit mystified when it comes to coolant systems and been wary of messing with them. It has green coolant in at the moment, to replace the thermostat, I was going to drain the system first and then its just 3 bolts and a hose clip to take out the housing and thermostat.

Once the new thermostat is in place, I planned on filling and bleeding through with distilled water, draining that out to get rid of any c*** that might have built up and then refilling and bleeding with 50/50 coolant/water mix.

Is that a wise idea, is there anything that I should be aware of when I do that and what do I need to look for when buying new coolant?

Thanks in advance for any advice.

Davy

Reply | Report as offensive | Link
Wed 18 Oct 2023 21:45
BMW E36 1998 316i - Coolant Flush - Metropolis.

Everything you are saying is on the right track. Not that you were looking to, but I would emphasise don't change the type of coolant, stick with the factory recommended for this model year and if you can, buy the pre-mixed stuff.

You might find there are engine block drains, which if you open should get more coolant out. You'll usually find accumulated crud there as well. I know nothing about your specific engine though.

Reply | Report as offensive | Link
Wed 18 Oct 2023 21:53
BMW E36 1998 316i - Coolant Flush - elekie&a/c doctor
If the coolant looks clean , I would try to avoid flushing the system, because this model can be a real pain to bleed out the air . Use any recommendations for ethylene glycol anti freeze (g48 or similar) . There’s a cross head plastic bleed screw on top of the radiator. May be an idea to see if this can be removed without it snapping off before you commence any work .
Reply | Report as offensive | Link
Sat 21 Oct 2023 06:49
BMW E36 1998 316i - Coolant Flush - edlithgow

No experience with this engine, but if you think it might be sludgy and you MUST flush it, if you can get a hose to it, initially flushing it out with a strong flow of tap water might be worth doing,

I had a lot of trouble on my Daihatsu getting air out of the system, and eventually settled on disabling the cooling fan so the coolant would boil, with a large funnel jammed in the radiator fill port to give it expansion room.

This was a bit alarming, but I think preferable to running for an extended period with air pockets in the cooling system. I've read somewhere that cracks in the cylinder heads around the exhaust valves are a known problem with BMW engines.

You can buy gadgets that will do a vacuum fill of the cooling system, and I suppose this must also be offered as a service by garages.

Heres Mr O describing his

www.youtube.com/watch?v=cPMSzA2wOmwff

A lot more stuff on Youtube about these

AFAIK the commercially available gizmos all need a supply of compressed air, BUT you can get water-operated venturi vacuum pumps pretty cheaply that might allo0w you to improvise something

Selection of coolant type is a bit of a mystery minefield. I suppose if you want to be safe you buy stuff with OEM labelling, from a BMW dealership. I disliked the Tainan Daihatsu dealer quite a lot, and it was apparently mutual, so I just used Shell green stuff

Reply | Report as offensive | Link
Sat 21 Oct 2023 16:20
BMW E36 1998 316i - Coolant Flush - John F

If the heater is working and the engine is being kept cool, there is clearly no significant build up of grot. I would just remove the thermostat, and see if I could unstick it. I might try a weak acid, e.g white vinegar. Anyway, I wouldn't risk upsetting the system and dislodging debris and introducing more corrosive oxygen by energetic flushing - I'd just top it up with more green coolant (e.g.Comma G38) after installing the working thermostat (test it in and out of pans of boiling and cold water). If you are doubtful about its efficacy, put a sample in your deep freeze.

Reply | Report as offensive | Link
Mon 23 Oct 2023 07:31
BMW E36 1998 316i - Coolant Flush - edlithgow

Anyway, I wouldn't risk upsetting the system and dislodging debris and introducing more corrosive oxygen by energetic flushing - I'd just top it up with more green coolant (e.g.Comma G38)

Hadn't thought of this, doubt its significant, and certainly wouldnt have done it for this reason alone, but, in boiling the coolant to get rid of air pockets (after my turbulent tap water flushing), I would also be removing any dissolved oxygen, (which would probably be present in the coolant with or without the turbulent tap water flushing)

Reply | Report as offensive | Link

Looking for a garage you can trust? Honest John's Good Garage Guide has thousands of reader recommended garages, plus how-to guides and tips on servicing.

The Good Garage Guide