The arrow in the following image shows where the thermostat housing was spraying coolant from. I have the replacement part ready to install but I'm wondering if this is a weak spot, is there any "hot glue" or epoxy that could be run along that trough and strengthen it before installing the new unit? It seems to me this is where the last one leaked as well.

 

I just strengthened a plastic part in my coolant system. Use JB Weld. No guarantees that it will prevent the part from splitting there again. However, it won't hurt anything. I believe it will be stronger than the original plastic. It looks like the part is cast as two parts. So they are likely gluing the two parts together at the factory anyways unless that is just a mold seam which is probably worse because it will likely be colder than the rest of the plastic on the mold. That point is directly the first point off the water pump so it will see the highest pressure.

 

I wish I had seen the JB-Weld suggestion before I recently replaced my TStat housing and water pipe. I would have run a bead of jb-weld where you mentioned in the photo. I would also have run a bead of it on the water-pipe end, that goes into water-pump, that seems to break apart. I'll make sure to do it next go around...

 

My guess would be that JB Weld will do nothing to help. If it's a BMW/MINI part with a warranty and it fails with JB Weld on it they will probably refuse to honor any warranty on the part. I surface welded two pieces of metal recently with JB and it would not budge, until I gave it a wack on the side with a hammer. It flew right off.

 

You need to scratch up parts especially metal parts before you JB Weld them and make sure and use alcohol to swap off any residue oils. I have used JB Weld on mufflers. The stuff is incredible.

Most of these warranties on all of these parts are worthless. Generally parts do NOT fail under warranties. They fail, one hour to one month RIGHT AFTER the warranty ends. If I see a part has an obvious point where it looks like it is going to fail, I am going to fix it before hand if I can. I don't have time to fix the same thing every x number of months or years for what the part is warrantied to fail on. I look at these warranties as guaranteed to fail dates.

I venture to say that you could JB Weld the broken part you have. The amount of heat coming off hot water will not effect normal JB Weld, but they have High Temp JB weld for other applications. Basically when you mix up JB Weld in this application, you are making Plastic. The same plastic you already have. On this particular application, I would cut fiberglass cloth to go on the length of the seam. After roughing it with sandpaper, clean it will alcohol, put a thin layer of JB weld down, use a heat gun if necessary to make it run into cracks, while wet, lay the fiber cloth cloth down, add another layer of JB weld on top. You have just created high temperature fiber glass probably 10-100 times stronger than the original plastic. Honestly, I doubt it splits there again.

Now that people say this is a high failure point, when mine fails, that is what I will do.

 

I had the same issue on one of my rebuilds with the thermostat housing. A leak like this tells me the bonding agent is beginning to reach end-of-life. Adding the JB Weld or any other glue may buy you a little time (if you are waiting on the new part to arrive or coordinate time to do the repair), but I wouldn’t trust it as a long term solution.
You may come out to your car while miles from home and find all the coolant on the ground. Keep the commutes local so you can limp home if the problem expands.

 

I agree with this because temperature makes things expand and shrink and plastic is affected more then metal. I would guess the JB weld for sure would eventually break loose or crack and they hot glue if survived that would not have the strength to do much. I love your guys ingenuity of trying to come up with a solution, but for a fix I would not count on it.
3 years ago I bought my mini to compete in SCCA H street (stock) autocross. Found a 2012 75k miles manual, no sunroof and only options sport seats and leather steering wheel when I ran the vin. $6200 was a good price at the time after searching for a couple months for the right car. Had not even got my plates yet and on my way home about 200 miles away , it had been raining , the wife was driving and we got stopped for construction on they highway. When we finally started to move the wife said she saw smoke from the car. Time I got my seatbelt off and turned around I did not see anything. 30-40 miles later both check engine lights go off and we pulled over to find oil and water all over engine compartment. No overheating light came on because it most likely dumped all the coolant at once. Luckily we had been following my friend in his mini and we got a ride home and the next day him and I got his truck and trailer and took the car to his shop. $2000 for good low millage moter and a $1000 to my friend to install and my good priced car was now an expensive one. I dont think these preventive fixes will work but they might keep from a big quick split like mine and dumping all the coolant at once giving you some kind of warning.

 

A test could be done on the old part. Glue 2 pcs with the JBweld in a lap joint. Then after cure pull them apart using a scale to measure force. If you want to go further, heat cycle it a few times & repeat test. There are many different plastic materials out there, not all of them can be glued.

 

Heating and Cooling Effects. Can JB Weld Fix a cracked 350 degree Heated and Cooled Cylinder Head? -
The Thermostat is already two parts glued together in manufacturing. To say glue won't work kind of speaks to the original part failure. Test it on the old part cut some small grooves in for the JB weld to hold on to but only on the side that broke. I'll bet your thermostat will split apart along the rest of the seam that was originally glued together in the first place in manufacturing before it splits at the fixed JB weld joint.

 

I've thought about this as well...I was thinking of spraying a lacquer or even rhino lining on these plastic parts but I don't think it would help. The plastic degrades over time, I believe because of the constant heating/cooling and expanding/contracting.
Your best bet is to buy the housing from FCP Euro, they have a lifetime warranty on parts which is basically unheard of. The VW guys really like them.
https://www.fcpeuro.com/Mini-parts/C...6&b=8&d=916&v=

 

I would get a new housing i would get a new one and we are here if you need any help. I just did mine on my R58 JCW. Dependent on model and Miles some are covered under the extended warranty from MINI. You have to call and ask MINI with your VIN to see if you are covered. If not we have you covered.

 

Speaking of thermostats which brand is the most reliable there are so many options.

 

I am running our bremmen one right now, no issues. Other then that the gates and genuine MINI one are fine. Just make sure you get the correct one for your year and some dependent on model and first time changed you might need the pigtail harness.

 

Thank you I was looking at yalls Bremman one as well. The three year warranty is pretty stellar.

 

It sounds like there are some cheap e-bay ones out there.

Lacquer isn't going to help or do anything. The problem is that joint where they heat glue the two parts together. That appears to be designed to fail. What to do is roughen both sides of that joint all the way around with sand-paper, cut strips of Fiberglass Cloth to go all the way around that joint, tack it down on both sides in a few places with some 5 min. epoxy. Then mix up JB Weld in a cup with a tiny bit of Methanol. Don't add too much as it weakens the final jb weld. Then use a disposable solder resin brush and brush the JB weld on top of the fiberglass cloth all the way around. You just created a fiberglass c-clamp on to the thermostat build seam. It will outlive all the rest of the plastic on the thermostat. You have just created a life-time guarantee part. Now that I see the problem, when I need to replace mine that is what I will do.

Fiberglass cloth

 

I'm looking at ordering the Bremmen from you; did you replace the crosspipe along the back of the engine as well? And if you did, which part did you use? I have an '09 R55, and believe I don't need no harness.

Thanks,
Mike