E36 M3 Expansion Tank

[wrs 120]

Replaced my radiator with a custom build from A1 Radiators. Decided to go with the M3 Expansion tank since it's self bleeding.

Since the change I'm getting a little overflow from the expansion tank overflow tube from time to time. I'm only running the 1.4 bar radiator cap - should I change to the 2 bar type?

Most of the time there is no overflow, only if I give it stick for a while and then stop before the cooling system has caught up (coolant up to 95'C). The when hot, the radiator hoses are firm but not hard. It's still possible to squeeze them and you can see the coolant level rise slightly in the expansion tank. If I squeeze both radiator hoses as hard as I can (to try to raise the pressure in the cooling system) no coolant escapes from the overflow hose. I'm running Autostar Long-Life 50/50 pre-mix coolant with 1/2 bottle of water wetter added. I have 3L of BMW blue coolant additive and considering changing to this after flushing. Didn't have the BMW additive when I did the radiator install otherwise I would have used it.

Any suggestion what could be causing coolant to overflow occasionally?

[thorburn 121]

I'm currently looking into getting a euro expansion tank for an aftermarket radiator. 

I did notice where I was searching in realoem the caps all seem to be 2 bar. 

Higher boiling point from that extra pressure might be all it takes. 

Are you using a mechanical or electric fan? 

 

Sorry I'm of no help. But would be keen to find out before I head in the same direction

[wrs 120]

Not sure the small gain in pressure would help all that much. The 50/50 coolant mix I'm using already has a boiling point of 122'C which should be higher still under pressure. If it is boiling issues then I'd be quite worried as we'd be talking near 130'C if that's the case. I've had my tablet connected to the Link ECU so I can monitor ECT and it never goes over 95'C when driving.

I suspect the issue was to do with trapped air in the head which has subsequently cleared because I haven't had any more overflows in the last couple of days. I didn't raise the front of the car when filling the system so it's possible some air was trapped.

I did a fan delete about 5 years ago and have been using front mounted electric controlled by the Link ECU ever since.

 

I've got new radiator hoses arriving the in the next couple of days and will be changing the coolant to the blue BMW stuff when these are fitted. I'll also raise the front of the car this time to see if this helps with the overflow issue. If there are still overflows after this then I'll change the radiator cap because it might be faulty.

When fitting the Euro expansion tank you'll need to find/make the ledge support it sits on. Most likely your car will have the mounting bracket on the firewall already which is easy to use (2 x M6 screws). However, you'll need to fabricate a bracket to bolt onto the strut tower to support the other end of the ledge. I fabricated my own ledge because I couldn't find anyone with a second hand one. I used 3mm ally plate for the ledge and 25x25x3mm ally angle for the strut tower bracket. For the expansion tank mounting you'll need to make a support at the back of the ledge for the two round bits to slide into + a clamp at the front for the foot. You also have to make a bracket off the side of the ledge to hold the round plug for the ECU connection (and a second one for the other round plug if you car is auto) as this/these need to be relocated.

[M3AN 4016]

5 hours ago, wrs said:

...However, you'll need to fabricate a bracket to bolt onto the strut tower to support the other end of the ledge. I fabricated my own ledge because I couldn't find anyone with a second hand one...

That's a good point actually. I think you can get it from BMW but IIRC the part number is almost impossible to find. Only the M3 shells came with the tower bracket and a guy in the UK ended up reshelling his M3 with a standard 3er and getting a genuine new part that took him forever to find. I'll see if I can find the discussion but yes, assume you'll probably need to fab something up.

[wrs 120]

Replacement hoses arrived today. Drained and flushed out the old coolant with distilled water. Refilled with 50/50 BMW blue coolant and distilled water. Went for a bit of a drive and so far no issues. I raised the front of the car this time and tried to make sure there was no trapped air. Time will tell if it still overflows.

Can take some photo's of the ledge and bracket I made up if you like? I won't be able to remove the expansion tank but should be able to get enough detail for you to DIY...

[wrs 120]

Took some photo's so here's a step-by-step to fabricate a bracket to hold the M3 Euro Expansion Tank. Turns out it was easy to remove and there was enough length in the hose to push it up onto the inlet manifold so I could take photo's.

Your car should already have a bracket on the firewall where the back of the mounting ledge bolts to with 2 x M6 screw.

If you fabricate a flat plate ledge (eg 3mm Ally sheet) you need to put a 6mm spacer between the bracket and ledge so it sits at the correct height. I used cardboard and tape to make a template of the plate. This was overlaid onto the 3mm Ally Sheet and traced out. The Ally Sheet was cut out with a Jigsaw. The firewall bracket mounting holes were marked out with the plate sitting in-place. The strut tower end had hole marked out about where they would need to be. Once the holes were drilled and the plate screw in to the firewall bracket I marked through the strut tower holes onto the strut tower bracket. This bracket was only temporarily bolted in so it was removed to drill the holes for the ledge.

Next the position for the expansion tank was marked out on the ledge with the tank sitting roughly in place. I marked only the foot end and then removed the ledge to get everything else lined up on the bench. The bracket for the rear expansion tank mounts was cut to suit along with the PVC mount. The rear bracket was bolted on and the ledge was ready to reinstall.

Top View of the completed ledge:

You can see the bracket bolted and glued to the strut tower. The ledge is made from 3mm Ally sheet. The Bracket to hold the ECU plug is made from 25x50x3mm Ally Angle with the bit that slides into the plug mounting grooves made from standard electrical DIN Rail cut to reduce the width. The Bracket to hold the back of the expansion tank is made from 25x100x3mm channel with one end cut off and a piece of 25x25x3mm Ally Angle bolted to it facing backwards. The bracket has to be bent to match the angle of the two round things on the back of the expansion tank. The grey plastic is 10mm PVC sheet. I put a nylock on the M5x40 bolt holding the PVC so it could be left just nipped up and could swivel so the expansion tank can be slid in at an angle then turned into place. At the strut end there's a flat plate added to allow for the thickness of the foot of the expansion tank. You need to make a small plate up to screw on to this plate to clamp the foot.

Bolts holding the back of the ledge to the firewall (6mm spacer underneath):

Finished Install (except the missing coolant low plug!!)

The coolant low brown/white wire needs to be pulled back from the radiator drivers side and a new ground wire added/

Height the expansion tank sits at:

 

 

Edited June 10, 2020 by wrs
Added more detail

[thorburn 121]

Thanks for the bracket overview. 

[wrs 120]

No worries, welcome.

Haven't had any more overflow issues since putting in the new hoses and coolant and raising the front of the car while filling. I suspect I must have had air trapped in the head from the first time round.

Turns out the ledge panel is easy to get to so I can remove it easily and trace round it on cardboard and send to anyone who wants to fabricate their own - just ask. If anyone does want a template it might also be worth while drawing up and posting the drawing. Then I can also include the bracket dims etc...

[thorburn 121]

Where did you order your expansion tank? I've got access to a used one. But I've got new parts for the rest of the cooling system. No reason to stop

[wrs 120]

Are you sitting down?? $235 from BMW...

I also found the cardboard template I made for the ledge - your's if you want it.

Edited June 11, 2020 by wrs

[B.M.W Ltd 950]

The bracket would look better done on a 3D printer in black or a colour to suit the engine bay colour

[thorburn 121]

That isn't too bad. Only a little more than some overseas options. 

I'm a welder/fabricator by trade. So should be able to make up a bracket. Those photos were definitely helpful though. 

I've also got a 3d printer with a roll of petg as well. So there are options.

[polley 916]

The m3 e36 expansion tank appears to be the same as an e30 one.

[wrs 120]

Yes, E30/E36 is the same. Don't have a 3D printer... I thought about painting the bracket black to hide it but actually like the raw ally look. Each to their own though - can certainly understand why matching to the vehicle colour would be appealing too.

[wrs 120]

Here's a drawing of the ledge that worked for me - save's you the time making a template...

[thorburn 121]

Legend. 

[Gaz 1061]

Im looking doing this as my radiator is on on blink do nows a good of a time as any. Any tips on what parts to order?

A mate found the part number for the ledge if anyone was interested 51712259957. About $250 new...