I have a 2008 R56 MCS and it is leaking massive amounts of Coolant when it warms up. I have no idea where is coming from. All I know it is not from the radiator.

Any ideas on where to check?

Tried getting underneath and looking:

 

Water pump housing is usually the culprit in my experience. Or could be bottom of the reservoir.

 

The expansion tank looks fine as well as the radiator.
Very uncomfortable under the car. Can't get a good look. Don't want to remove the plastic intake manifold, but I guess I'll have to.
Where is the water pump housing located?

 

Based on your second video it looks like it's coming from thermostat side. The cross over pipe (the plastic pipe with the coolant dripping off) can also leak at the block side, but that looks dry. Nevertheless I would replace both thermostat and pipe. I'd suggest taking the manifold off, easier to get to all this piping.

This job is doable. But my personal least favorite one. And use the right fluid after draining. Zerex G48 is blue.

 

My mistake, I meant thermostat housing. You can see it from the top on the drivers side.

 

My brother replaced the thermostat housing like 2 years ago...
Which black plastic pipe? I thought that was the drive shaft.
If I remove the intake would I need to order the gasket?
Thanks.

 

Found video. I hope it is the water pipe and not the thermostat housing again...
if I do it, I'll probably need to replace both. LOL.

 

The cross over pipe and thermostat are held together by a metal clip that slots into the plastic pieces. Maybe that wasn't assembled properly, and unseated itself and started leaking. Or the housing itself developed a crack, but 2 years sounds too short. Unless it was a cheap housing. Maybe worth checking the coolant hoses at the heater outlet, just to make sure the clamps are seated properly.

 

I have the same leak, on a 2008 R55 Mini Cooper Clubman S. Took several trips to the mechanic to figure it out.

The symptoms seemed maddeningly illogical: leaks found under the car only when sitting overnight or for several days in specific weather conditions. Warm: it leaks. Cold: doesn't leak.

Due to pandemic, haven't been driving much. In one instance, it leaked the entire content of the overflow tank just sitting there.

But no leaks when driving, and passed pressure test multiple times.

I had a crazy working theory that maybe it was some hairline crack at an angle, and when the system became pressurized, the pressure actually CLOSED the crack. In retrospect, and after talking to other, I think my crazy theory was crazy. Most likely a rubber seal that expands when hot and thus temporarily solves the problem while driving.

Separately, I decided to replace the valve cover (replaced the gasket only a couple years ago). the gasket was leaking again, and found suggestions online that the valve cover itself ought to be replaced as well, and as well some concerns about the insanely-complex PCV system built-in to the valve cover. Mechanic indicated that failure of the PVC could cause crankcase over-pressure, and could be adding to oil leak issues. This was prompted by discussion with the mechanic, and we agreed it would be good to take care of the valve cover and clean up all the oil on the outside fo the engine to make it easier to identify the coolant leak. After reading reviews, I figured that the aftermarket valve covers are all likely the same product and so I chose one of the cheaper ones with good reviews. $49 with the gasket pre-installed. I know the bit where multiple Chinese factories work from the same (or OEM) plans, somebody gets paid for the plans, and the intellectual property laws are weak... The risk is incorrect materials or sloppy manufacturing. So, I looked for lots of sales and good reviews on Amazon. Last time, the gasket alone was $30! Mechanic was pleased with the quality.

I was able to catch the leak in action, and took photos and even a little video. So, now I could at least point to where the drips were coming from, so I showed the mechanic when up on the hoist. But, still, he was unable to locate the leak.

Finally, I did an Internet search and found this (and other accounts of the same leak). So, armed with that knowledge I pointed and mentioned more than a few times that I found an Internet thread that described the problem exactly, and he was able to positively identify the leak.

I had ordered some UV dye and a UV flashlight in case he wouldn't be able to find the leak. I'll be putting the dye in once the repair is made, to help determine if there are any other leaks.

Mechanic said I should replace both the tube and the thermostat housing - even though housing replaced 2 years ago, because they often crack at the lip when removed.

Question: anything else recommended to replace at the same time, since I will be paying a pretty good sum for the labor? Mechanic is OK with me buying parts, but of course, he can't warranty the job with third-party parts I'm fine with that - he is a fair and honest guy with decent prices, doesn't find unnecessary stuff to fix, etc.

I've already had both coolant hoses for the turbo replaced. Top one recently. Bottom one replaced some years ago with a Detroit Tuned metal "permanent replacement". (Oh, wait, maybe confused, maybe that is an oil line?) As well, the water pump was recently replaced. I like to do small upgrades when possible, so for example, a long time ago I had a need for brake hoses, so I upgraded to metal-braided ones. So, if there are water hoses that should be replaced or can be easily replaced with this job, I would probably opt for silicone (unless some good reason NOT to). If for no other reason that they look cool.

Anything else in that area that would be good to proactively service?

 

Got one of those borescope camera. Seems to be the water pipe leaking from the thermostat housing side.

 

You probably know, but two small tips:
the cheap pipes are fine. For my part I had to remove some burrs in the o-ring groove at the block side, but other than that it was fine.

For the o-rings I suggest using silicone paste. Makes it so much easier to insert into the block.

As you already have a borescope: verify that the o-ring on block side is completely inserted. I once had it that thebo-ring wasn't lubed properly, and I pinched it with half of it being rolled over the groove.

 

Doh! I actually have one, if I can find it. Or, get it back from whoever I loaned it to.

Anyway, diagnosed, would have saved a lot of trouble. I'm gonna find that thing, or get a new one. Was really invaluable probing inside walls to know what I was dealing with before mounting a heavy TV (plasma dinosaur...)

 

Update:So, I removed the thermostat housing and found this.







I think I remember my brother saying he had to use silicone, but don't remember why. So I'm guessing that failed.

Any way I can just get an O ring instead of the whole thermostat?

Not sure if I should even bother with the water pipe now...

 

You mean the gasket? The blue gasket on the thermostat housing?

Yes, I have seen them online.

I just ordered a thermostat housing and pipe from AutohausAZ, I think perhaps better than the Chinese ones on Amazon. They are at least German.

I noticed that they also sell both the blue gasket that goes with the thermostat housing, as well as the o-ring for the pipe.

I spoke with someone on the phone, and at first they really implored me to get genuine Mini parts. But in this case, I am skeptical, because I know it's a bad design...

They recommended Rein:

https://www.autohausaz.com/pn/RA-11537589713 $21.19

over Febi Bilstein.

And I ordered a Facet thermostat housing $71.99 (Chinese ones are ~$40 on Amazon)

https://www.autohausaz.com/pn/11537534521A

I have to say from the photos, the genuine Mini looks nicer...

Not sure now where I found the blue gasket and the o-ring separately, but I have seen them and quite inexpensive.

However, so many posts I have read about this suggest the plastic parts will crack when removed and the get brittle from the heat, and so should be replaced, as it's a fairly costly job to have somebody do, and time-consuming and fiddly to do yourself. So, just replace the parts.

That silicone sealant sure is a hack job IMO. Maybe your brother should stick to caulking bathtubs?

If you want an upgraded o-ring, and you can be certain of the size, McMaster Carr is a great source. But I will let others suggest the best material, don't wanna step into that... Not a car parts store, just a great resource for all sorts of common (and uncommon) mechanical parts, I guess the "machinist's friend". Was recommended to me by a friend who is a Materials Scientist, and has to build or refurbish stuff (like vacuum pumps) from time to time. I could tell you what industrial filter bags to use for making Greek Yogurt if you are interested, LOL.

 

I was referring to the water pipe o ring on the thermostat. The thermostat gasket was stuck to the block and didn't want to remove it since it had a bit of silicone. Didn't seem to be leaking there.
I did remove the water pipe and the end from the water pump broke off and the o ring fell. That O-ring was very brittle. It was a matter of time when that was going to fail. I replaced it with a cheap one. The brand is Brugaflex.

I purchased that thermostat housing a year and a half ago on Rock Auto. The brand is Facet. It was one of the most expensive at the time. Technically it is still under warranty. I was told that the temp sensor is supposed to be brown. Not sure if I should replace the thermostat housing. I don't get free shipping where I live so the O-ring (11518613804) on the thermostat housing going to the water pipe will cost me about 20 bucks and 2 weeks to get here.

 

First step is to remove your brothers access to silicone.

I think a thermostat is about $80 or so? Looking at the residue from the old silicone around the gasket area, maybe bite the bullet.

Normally you shouldn't need silicone around those gaskets, and also none where it meets the block.

 

Ended up buying an ECS Tunning Assembled Bremmen. Comes with 3 year warranty and has the brown temp sensor. Should get here by next week.

I assume the silicone was used cause of bad tolerances and I guess was leaking. That thermostat was about $90.

 

Using silicone there won't fix crap. I can't tell because of all the silicone, but typically a connection like that will have an o-ring, and if it leaks you can often just replace the o-ring.

Like 90% of the time silicone is used by amateur mechanics it's used wrong. I swear, they should make you take a written test before you buy the stuff.

Your brother definitely did not do you any favors when he did that repair, I'm afraid.

 

Received my parts to AutoHausAZ already. Ordered on the 28th, shipped on the 29th, received today!

The thermostat housing is a Facet, and is marked "made in Italy".

The pipe is a Rein, made in Turkey.

The pipe has an o-ring preinstalled on one end, and a loose metal clip.

The housing has a blue/green connector. It LOOKS like the brown one I have seen in pictures. (I have a 2008 Clubman S). And the blue gasket installed.

Is there some additional o-ring I might need for the pipe? I already had the water pump replaced a few months ago. Is there an o-ring that ought to be replaced? Is even a few months too long to re-use, given stress of disassembly/reassembly? (The pipe goes between thermostat housing and water pump, right?)

I see the Bremmen referenced above comes with bolts. Should I replace bolts?

Anything else recommended? I am thinking are there any hoses that are easy to replace that ought to just be done while the coolant is drained?

 

The end of the pipe with the o-ring goes into the block at the water pump side. Remove all silicone if someone also used it there...

The thermostat has an o-ring where it goes into the pipe.
​​​​​​the clip needs to be removed.

First get the pipe into the block. Then the thermostat into the pipe. Then secure lightly with bolts. Then put the clip in.

Use lots of silicone paste (the vaseline style stuff) on the o-rings. Like
​​​​​​

 

I would do the bolts unless the ones are fine. most people have the bolts and they might be all nasty on the threads. Make sure everting is clean and the contact surface is clean against the block. Grease helps insert the rubber into the tight slots. Should all fit snug.

 

I hope you have the metal clip for the water pipe that secures it to the thermostat housing