The $4 Fix for Radiators Leaking from Expansion Tank (so far atleast) Pics!

[mzarifkar]

Edit: 6 months and a few thousand miles later, still working great

Been a productive break really,

Took out the radiator to take on what i perceived to be a leak from where my expansion tank meets the radiator, a slow but steady leak that resulted in many concerned remarks at college when there was a puddle of radioactive green under the car.

I suspected this was the said joint because cold weather would aggravate it (thermal expansion differentials..) and i approximated the coolant to be leaking from that area.

Now keep in mind this is on a 1995 525i, not sure if this will help your model

First I took the radiator out, starting by draining it. You can see the blueish drain plug in the picture. note that there is a small clip on the left side of it that you need to pull out in order to fully remove the drain plug.

The clips on top that hold down the radiator ( small black things, quite stylish design..) are near impossible to remove, i broke one and cost me $4 at the dealer to replace. Bentley manual says to take off the fanshroud along with fan too! I managed to just loosen the shroud by taking out the two ever so fragile bmw plastic rivets which attach it to the radiator, this gave me enough room to work with.

Disconnect all hoses (there are 3 of them, a little bugger on the bottom left)
Take off the transmission oil cooler, mounted on the front of the radiator (2 screws on top, some wiggeling to get bottom off) It helped when i took out the airbox front half.



Here is the void, notice the transmission radiator.

Now take your new found radiator and take the two hex screws out of the top of the expansion tank. take off the fill cap if not already.
now the expansion tank will slide up. it wont go easy, i had to do some prying with a screwdriver, be careful, don't break stuff.



here is the radiator with tank removed



here is the bottom of the expansion tank, notice the o ring has been compressed into the o-ring groove, causing the leak.



this is where the bottom of the tank lives on the radiator, the goop i fished out and cleaned with Q-tips, was the radiator sealant i tried, atleast it found the leak..


before putting it back together i rinsed out the radiator with a lot of water clearing out a lot of the sealant goop. then i greased the new o-ring and carefully tapped it back in place with a hammer (using a block of wood to protect tank) i takes quite some effort to get it back in, which makes me all the more confident of a proper seal.

installation is reverse of removal. the pain in the ass top mount clips takes a good bunch of prodding to install back on, i had a BMW mechanic show me (so he would break it if he failed) he used a screwdriver to push down in the hold on the clip and then some

Fill radiator, and bleed properly, then bleed it again!

Enjoy fixed radiator

-em


PS, in retrospect, i feel that perhaps i could have completed this by just draining radiator, taking off the screws on top of the tank, and then wiggeling the tank out while leaving the radiator put. Little something to consider, it will save you time. But by taking out the radiator i was able to clean it and inspect it.

[mzarifkar]

here is the tank with new o-ring, approx $4 from dealer

[bigtisas]

Good job.

Personally, I think the BMW cooling system is a bad design.

[Kalevera]

I think you will probably want to flush the car's cooling system a time or two, if evidence of that sealant isn't enough. ALWAYS a bad idea to use that junk, cooling system parts are much cheaper than engine work.

[mzarifkar]

I have a 800mile drive to Iowa this Sunday, i will probably flush upon arrival and just to see how much of that sealant is coming out.

[DanQ]

Thanks for the write-up. I've been losing coolant very slowly since I purchased the car in 2004 and I suspect this is where it is leaking (I can sometimes smell coolant at the front of the car)

[Russell]

Tank can warp and not seal well even with a new gasket per my local indy. They then need to replace the entire expansion tank at about $60 parts.

[spudman27]

Exactly what I was looking for and in the process of doing on mine. I'm trying to figure out how to remove the expansion tank without removing the radiator. Parts blowup indicates the top black piece as separate from the tank & radiator, but darned if I can figure out how to separate it from the assembly. I've removed the two allen screws and bleeder and it wiggles, but that's about it.

Any tips?

[DaveVoorhis]

It should pop off with a screwdriver. You have removed the radiator clip and the plastic fan shroud rivet, yes?

[Alexlind123]

Good job.

Personally, I think the BMW cooling system is a bad design.

On which car?