Recommendations for sealing loose connection on thermostat housing

[grantmiller1]

I ran into a issue with a new thermostat housing (325i M20) that has a loose connection that will highly likely leak.

Attaching pictures of the loose connection.

I'm thinking of using J-B Weld TankWeld or RadiatorWeld, any other ideas?

I think normal J-B Weld won't last long with exposure to coolant.

[82eye]

oh no ... was it a uro housing ?

i picked one up myself as the original had decayed due to the PO's use of a non aluminum friendly coolant. oem units were prohibitively expensive and not available. the casting of the uro part was seriously poor and we had to dremel excess from the interior and smooth the passages proper.

permatex makes a coolant safe silicone gasket type material that may help. jb weld has a coolant specific product that may work, regular jb weld deteriorates quickly in contact with a coolant. there is not a great deal of confidence in how long either will last.

edit : the real answer is replacing the housing with a quality part. it's an absolute pain as you either have to remove the intake or fuel rail for clearance, or remove and replace the studs holding the housing to get it out. make sure to order the studs with the housing if you go this route, as they rarely remove without bending, making them useless.

[grantmiller1]

oh no ... was it a uro housing ?

i picked one up myself as the original had decayed due to the PO's use of a non aluminum friendly coolant. oem units were prohibitively expensive and not available. the casting of the uro part was seriously poor and we had to dremel excess from the interior and smooth the passages proper.

permatex makes a coolant safe silicone gasket type material that may help. jb weld has a coolant specific product that may work, regular jb weld deteriorates quickly in contact with a coolant. there is not a great deal of confidence in how long either will last.

edit : the real answer is replacing the housing with a quality part. it's an absolute pain as you either have to remove the intake or fuel rail for clearance, or remove and replace the studs holding the housing to get it out. make sure to order the studs with the housing if you go this route, as they rarely remove without bending, making them useless.

Yeah, it is a Uro housing.....

The casting/machining on the housing was not that great, I had to use a file and a Dremel to get temp sensors to fit flush to the housing.

My research on JB Weld found the same thing, their RadiatorWeld (not the one for plastics) is supposed to work with aluminum and coolant. I also share the same concern about longevity.

My thoughts for a more durable/permanent solution are:

1. Get a proper thermostat housing (I think I saw a BMW housing on FCP Euro for $120-ish)
2. Pull this one out (after I went through the pain of getting it on there) and tap & thread that hole/fitting.

The tragedy of this shit sundae is that I just got the intake back on....

Thanks for the info and advice.

[grantmiller1]

Technically, it's a Ronak housing and Uro thermostat cap.

[82eye]

i just checked and mine is epoxied in as well. crap.

edit : honestly at this point i'd try a couple layers of epoxy anyway. a quick light coat then another on top and mate it back up. there's nothing to lose. just let it set up good before running.

if that doesn't hold then you could plan b the tap.


more edit : nice clean engine btw

[grantmiller1]

i just checked and mine is epoxied in as well. crap.

edit : honestly at this point i'd try a couple layers of epoxy anyway. a quick light coat then another on top and mate it back up. there's nothing to lose. just let it set up good before running.

if that doesn't hold then you could plan b the tap.

Do you recall what type of epoxy you used? How is it holding up?


I'll be adding coolant this evening for the first time and will see how things hold. I could only get J-B Weld TankWeld at my local AutoZone (I ordered J-B Weld RadiatorWeld online, should get here by Friday).

more edit : nice clean engine btw

Thanks! I finally got the intake and valve cover media blasted and powder coated, I swear I'm almost done with this car!! :)

[82eye]

Do you recall what type of epoxy you used? How is it holding up?

it's just the internal epoxy the mfgr used. i believe the original housings were a press fit.

[Panici]

Thanks! I finally got the intake and valve cover media blasted and powder coated, I swear I'm almost done with this car!! :)

Powdercoat job looks good. Almost done is also promising.

[grantmiller1]

Powdercoat job looks good. Almost done is also promising.

Thanks! Agreed, I'm itching to drive the car, it's been off the road for more than a month.

[grantmiller1]

This is hopefully my final update on this.


I decided to get the BMW thermostat housing rather than roll the dice on my patch job on the Ronak housing. Installed it tonight, waiting 24+ hours for the gasket sealer to cure (Permatex 22071) before adding coolant.


Thanks for all of the advice and tips.

[moatilliatta]

What’s the gasket sealant needed for?

Id consider drilling it and taping it for an NPT to barb fitting if enough meat there.