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M135i coolant change

15K views 24 replies 7 participants last post by  nazali 
#1 ·
BMW seem to think there is no need to change the coolant on our cars, despite the manufacturer Glysantin recommending it is done every 3 to 4 years because of its properties breaking down and becoming acidic.

Water pump failures are common on E series cars including on the N55 engine so I consider a coolant change good insurance.

I completed the change on my M Lite today. I didn't manage to get all the coolant out unfortunately though, I drained 4.5ltr by pulling the main hose off the water pump, system capacity is 6.7ltr. So not perfect but a damn site better than BMW's lifetime fill idea. Here's how to do it.

Preparation:
Required;
5ltr distilled water
3ltr BMW coolant - don't mix coolants so stick with OEM. Part number for 1.5ltrs is 83512355290.

8mm socket for engine cover bolts
Flat blade screw driver for jubilee clips
Safety glasses to prevent coolant getting in your eyes

Make sure your engine is cold before attempting this.

First, the process involves bleeding the system by running the water pump off the battery for 12 minutes, so make sure you're battery is charged before starting. Or hook up a trickle charger that is safe to use with the ignition on.

1. Safely raise the car for access under the engine.
I did this with the car on ramps in my garage. Access was tight but doable.

2. Remove the floor panel under the engine by removing the 8mm bolts, there's about 15 to remove.

3. Remove second plastic sump panel held on by 3 x 8mm bolts. You will now be able to see the water pump above the steering rack. It's on the LH side of engine. I'll upload a photo when I get chance.

4. Get a container ready to catch the coolant and put on your eye protection. Loosen the jubilee clip on the main hose which points rearwards. Coolant will trickle.

5. Pull the hose straight off, it's not threaded, just wiggle it off. Mine came off fairly easily. Coolant will gush out.

6. Open the coolant reservoir fill cap to let the coolant drain quicker.

7. To get the most coolant out the second hose attached to the water pump should also be removed but I couldn't get this one to budge so left it for fear of damaging it or not being able to get it back on. It's harder to access than the main hose too.

8. When the coolant has stopped draining, refit the hose and jubilee clip.

9. Open the bleed screw on the reservoir, located next to the fill cap. Fill the system with 50:50 mix of BMW coolant and distilled water up to the max line.

10. Next is the bleed procedure. Replace bleed screw and fill cap. Start the ignition without starting the engine. Turn on the headlights. Set the heater to max temp and fan to lowest setting. Hold accelerator down for 10s or until water pump starts.

11. The car will run an automated bleed cycle which lasts about 12 minutes. You will hear the pump running and coolant flowing as well as air moving.

12. When complete, top up coolant to max line. Mine needed another 300ml.

13. Check battery level, charge if required and rerun bleed cycle. This isn't fully necessary but I did it as a precaution to make sure all trapped air was removed.

14. Start engine and idle for a couple of minutes. Check for leaks.

15. Refit the engine covers. You have now given your cooling system a clean bill of health!

The whole thing took me an hour taking my time. If you're keeping your car as a long termer it's an hour well spent in my opinion.
 
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#5 ·
I did mine today, thanks for the guide. :thumbs: I did it very slightly differently:

Working entirely from the top, I removed the air duct pipe (& top to the air box) for access.

Then I removed the pipe from the bottom of the Thermostat (by easing back one wee lock-clip) which allows just over 4L of coolant out (which trickles out over your plastic undertray).

Whole job, 30mins max. 2/10 difficulty.
 
#6 ·
marco_polo said:
I did mine today, thanks for the guide. :thumbs: I did it very slightly differently:

Working entirely from the top, I removed the main charge pipe (& top ot the air box) for access.

Then I removed the pipe from the bottom of the Thermostat (by easing back one wee lock-clip) which allows just over 4L of coolant out (which trickles out over your plastic undertray).

Whole job, 30mins max. 2/10 difficulty.
Good work. Your method sounds much easier than mine and refreshed almost as much coolant. I might give this a go next time.

I do like how easy these cars are for basic maintenance such as changing fluids.
 
#7 ·
I'm going to replace my coolant this weekend, but want to get as much out as possible, so am going to drain via the water pump hose, then refill with distilled water, then drain again, before refilling with the correct ratio of coolant and water.

My question is, once I've first drained and refilled, should I bother with the 12 minute bleeding process, or can I just run the engine for a couple of minutes to mix up the coolant, before re-draining?

Do I run the risk of damaging the water pump or anything else by running the engine without draining, just for a couple of minutes?
 
#8 ·
As it's very tricky to get all the old coolant (or in your case Flush) out, aren't you concerned your final mix will be too weak? Or are you doing lots of clever calculations to ensure the final result is 50:50?

I'd just flush with 50:50 personally. Slightly more expensive, but far harder for a simpleton like me to screw up.
 
#9 ·
Well I've got 5l of concentrate so I should have enough for a flush with 50:50 with 5l or less drained, but even then, am I ok to run the engine after (without bleeding) to mix it all up...before then draining, refilling and then bleeding?

You're right, it'd be a lot safer to premix 50:50!
 
#12 ·
Want to get my coolant changed this year, thanks for the guide op.

marco_polo said:
Working entirely from the top, I removed the main charge pipe (& top ot the air box) for access.

Then I removed the pipe from the bottom of the Thermostat (by easing back one wee lock-clip) which allows just over 4L of coolant out (which trickles out over your plastic undertray).

Whole job, 30mins max. 2/10 difficulty.
Trying to figure out whereabouts this hose is you bled from, mp. Having swapped out a charge pipe (IC to throttle body) myself, I know they're a right faff, is that the pipe you mean? Removing the airbox and ducting that runs across the front of the engine bay is quick and simple enough.

Using this method, was it easy enough to catch the coolant as it ran down onto the undertray?
 
#13 ·
mtechtone said:
Want to get my coolant changed this year, thanks for the guide op.

marco_polo said:
Working entirely from the top, I removed the air duct pipe (& top to the air box) for access.

Then I removed the pipe from the bottom of the Thermostat (by easing back one wee lock-clip) which allows just over 4L of coolant out (which trickles out over your plastic undertray).

Whole job, 30mins max. 2/10 difficulty.
Trying to figure out whereabouts this hose is you bled from, mp. Having swapped out a charge pipe (IC to throttle body) myself, I know they're a right faff, is that the pipe you mean? Removing the airbox and ducting that runs across the front of the engine bay is quick and simple enough.

Using this method, was it easy enough to catch the coolant as it ran down onto the undertray?
Apologies, I meant the first air duct + airbox lid, not the charge pipe. The coolant just dumped all over the road randomly, washed it down the drains with a hose.
 
#14 ·
marco_polo said:
Apologies, I meant the first air duct + airbox lid, not the charge pipe. The coolant just dumped all over the road randomly, washed it down the drains with a hose.
Gotcha, thanks mp, did have me wondering which side of the engine we were on. I've done a pump and thermostat on an N52 and know that's also on the exhaust side.

And just to clarify, you disconnected the lower (red) or the forward facing (green) pipe?
 

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#19 ·
Thanks Marco, car going to my local garage this week to sort out reluctor ring and abs sensors as I had the classic symptoms diagnosed by stevesurrey! also new discs and pads going on. Will ask them to change the coolant as I' 'm sure its not been done in 12 yrs! All parts purchased by me and the garage are perfectly happy with this arrangement.

So far all oils changed including engine oil, filters, gearbox and diff. Any other suggestions regarding preventative maintenance would be very welcome!
 
#25 ·
but that doesnt mean you shouldn't, plenty of things that need to be done to a car or a BMW, which is not in any manual or recommended to do so, but is.. LOL
 
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