Coolant leak identification

C

Chengy

Member
 Warwickshire
Hi all,

Flushed the system with water and replaced the orange/brown coolant with blue, Comma G48 that meets BMW spec and recommended by others.

I’ll post a step by step later in case it’s any use - I felt like there wasn’t a definitive guide for the E85 M54, or at least something simple enough even an amateur like me could follow!

Bad news is that I seem to have a leak around this area, looks to be the bottom of the expansion tank - is it advisable to replace the tank and the reconnection of the hoses will fix this?

IMG-2220.jpg

Thanks all.
 
Check a bit closer if you can. It is more likely to be the seal in the bottom of the tank that has flattened. It's a push fit onto that lower housing and if it is that the water will be coming out a tiny bit higher up and running down.
I looked into replacing these seals but they are an odd size and whilst I found a company that could produce them I couldn't justify the minimum quantity they required.
You 'may' be lucky and it reseats itself over a few cycles, but in all likelihood you need to replace the tank.
Can't remember, but if it's an automatic then get the oil cooler thermostat that sits inside the bottom of the tank too, as they tend to pop apart when you remove the tank.
 
enuff_zed said:
Check a bit closer if you can. It is more likely to be the seal in the bottom of the tank that has flattened. It's a push fit onto that lower housing and if it is that the water will be coming out a tiny bit higher up and running down.
I looked into replacing these seals but they are an odd size and whilst I found a company that could produce them I couldn't justify the minimum quantity they required.
You 'may' be lucky and it reseats itself over a few cycles, but in all likelihood you need to replace the tank.
Can't remember, but if it's an automatic then get the oil cooler thermostat that sits inside the bottom of the tank too, as they tend to pop apart when you remove the tank.
Click to expand...

Martin,

Thank you for your advice as always.

I did have a much bigger leak before the flush - it happened after the VANOS refurb and I thought it might have been due to trapped air after disconnecting the lower coolant hose for access purposes.

So I thought I’d drain, flush and bleed properly to see if that’s the case. Leak is still there but a much smaller amount.

Still advise on changing the tank if it doesn’t get better after a few cycles?
 
Agree with Martin …possibly change the Tank …..the coupling on the cheaper Tanks is never perfect.
Go for a decent Brand as honestly I’ve been through the tribulations of buying cheap.
 
Umfaan said:
Agree with Martin …possibly change the Tank …..the coupling on the cheaper Tanks is never perfect.
Go for a decent Brand as honestly I’ve been through the tribulations of buying cheap.
Click to expand...

Thanks Umfaan. Yeah figured it might be the case of changing the tank.
 
Just to update this thread, found a hairline crack in the expansion tank that was spraying coolant forcefully out once system was pressurised, as you can see from the pic. Known issue with the expansion tanks it seems.

temp-Imageh-CR7-Pe.avif


Bought a Febi Bilstein one which seems good quality, I used part number 17117573751.

Replacing was straightforward for the most part - removing the expansion tank needed some well placed, controlled hits from below with a rubber mallet.

Sitting the expansion tank back into the mount and connecting the upper hose back into the radiator was a pain with these push fit style connections. Managed to bend and nearly snap off a plastic tab when I tried using pliers to pull two connections together, fortunately it's the outside tab of the radiator hose fitting and not part of the connection, so it hasn't impacted functionality.

Silicone grease is what you need, easy once some lubricant is applied to push connections together.

Carried out the following fill and bleed process whilst car was on axle stands.

1. Radiator cap and vent cap off
2. Engine off, ignition on, temperature set to highest, fan speed on but on lowest setting
3. Slowly fill expansion tank with coolant until bubble free coolant comes out of vent cap. Might be a bit messy until you get to this point.
4. Radiator cap and vent cap back on
5. Start engine and warm car up, checking you're getting hot air out of the vents when car is up to temp. Also check for leaks at this point under the car.

Took her out for a drive afterwards and temp was normal, as well as very hot air coming of the blowers. No sign of leaks. Successful day!
 
Could just be my experience but I don't think febi bilstein tanks are that good, mine lasted 900 miles before the hairline crack appeared, when put against a genuine bmw tank at 3 times the price you could tell why the bmw tank was more expensive, buy cheap buy twice I found out
 
Joez4 said:
Could just be my experience but I don't think febi bilstein tanks are that good, mine lasted 900 miles before the hairline crack appeared, when put against a genuine bmw tank at 3 times the price you could tell why the bmw tank was more expensive, buy cheap buy twice I found out
Click to expand...

Cheers Joe, will see how it holds out. Few posts on here said Febi Bilstein seemed good, time will tell! I needed to sort it quite quickly so I got one from eBay, otherwise would have ordered one from AutoDoc which has better prices for the OEM part
 
Chengy said:
Silicone grease is what you need, easy once some lubricant is applied to push connections together.
Click to expand...
Very true for quick connect fittings. Makes it much easier next time.

Chengy said:
Carried out the following fill and bleed process whilst car was on axle stands.
Click to expand...
Which engine do you have?
 
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