Anyone else have thermostat housing leak issues?

I have replaced the thermostat seals twice on my 91 TR in order to try to cure a persistent leak, in both cases they leaked around the seal between the two halves of the housing when I started the car.

The original seal was larger profile and square, part no. 4184495. The part it has been superseded with is 105192, which is smaller in thickness and barely protrudes from the lower half of the thermostat housing. FWIW, the housing is straight and undamaged.

Anyone else have this issue?

 

I think I will look for some nos original type seals. I don’t have the originals anymore and don’t like the idea of sealant.

 

Eurospares shows 4184495 as a superseded part, with 105192 as the replacement. When I search for a photo of 4184495 online I find a photo of similar seal which has a rectangular cross section and seems slightly taller (which would solve my problem). The thermostats are OEM Ferrari, bought from the dealer in Modena. They fit and operate perfectly, but the seal does not protrude sufficiently from the top of the case. I changed the timing belts in 2021 when my seals were changed and the problem arose. My engine is out again for another reason so I am just trying to solve it. It is not a huge leak, just an irritating, persistent drip every few seconds.

My choices are either to find a pair of 4184495 seals (difficult, but not impossible) or try to get the top of the seal to emerge from the case, either by installing an o ring below, or by putting a bead of sealant on top (but what sealant?). Opening the thermostat housing when the engine is in is not much fun.

 

It is quite odd. Maybe the groove in which my seal sits is extra deep on my car? I have owned it for 16 years, swapped thermostats at every belt change and have only experienced this issue recently with the new style seals.

To eliminate variables, I extracted the housing, removed the studs and checked both the top and bottom cases for flatness, they were perfect. The shop manual lacks a torque spec for the 10mm nuts which hold the cases together but as it is a 6mm stud, I use 10Nm in a crosswise pattern.

I am thinking of removing the assembly again and sealing the top and bottom cases with Henkel 510 (no 518 available here). In the longer term I will look for some of the original seals.

 

Exactly what mine looks like. The standard seal (105192) did not leak?

I sealed mine with a thin bead of Loctite 510. Once it has cured I will refill the system and see if it holds coolant.

 

I swap them out when I am in there, only because they are no fun to reach with the engine in place.

The Loctite 510 worked perfectly, so I can finish the car now.