Explore thermostat just won’t seal!

[Jdgephar]

As an aside - it's disheartening to see the inflationary costs with these parts over the past few years. I was looking at a thread from 2024 where someone mentioned that part and they stated it cost $23-24. It's now $38.99! And in my other thread on the solid state IVR - my hard copy 2024 Tom's catalog lists them for $39.99. WH and Tom's now sell them for ~$57. Roughly a ~50% increase in the cost of those parts in 2 years!

Made my own 5V IVR with a LM7805 and 2 capacitors. Works good so far.

 

[Broncobowsher]

FYI, the values of the caps are not even that critical. It isn't powering electronics, just a heating element. Any cap remotely close will do.

 

[joshua]

One of the molded silicone gaskets (dry), and a little rtv on bolt threads.

View attachment 963669

This, dry fixed the issue. Plus a piece of glass and 120, 180, 220 sandpaper on the new housing. I have a machined straight edge that I used to check the manifold and it was flat.

I didn’t silicone the bolts, as they don’t go all the way through the manifold. It was worth the 50 bucks for that gasket. I had to dig up different bolts as the other ones were to short. But it’s been holding for 10 minutes on the gauge, and I can’t see bubbles anywhere. Thanks gentleman!

 

[DirtDonk]

Congrats on the fix! Well, at least for the time being anyway. Hah!
Thanks for following up and letting us know how it worked out.

Paul

 

[joshua]

@toddz69, I can interpret your thumbsup reaction as RTV is only supposed to be applied on one side of gasket, or it should be applied on both sides.

I’ll be kicking myself for all the years of cursing when cleaning up intake side if I didn’t have to and should have only been applying it on the thermostat side. Can you elaborate which interpretation is correct?

The only reason I applied the rtv to the thermostat side only, is the intake was brand new, so was the thermostat housing, but that’s much easier to remove and just buy a new one. And I hate cleaning up rtv. I figured the new surface should seal and save me a bunch of cleaning the next time. I have no clue if it’s common practice.

When surface looks flat and not pitted, and if the part I’m working on is easily removed, I generally skip the rtv, especially if I can test it for leaks. Saves me from so much effen around the next time.

 

[ba123]

First time I've ever seen one of those - pricey bugger but if it works, it could be a good thing. I've certainly dealt with my share of leaky thermostat housings over the years.

As an aside - it's disheartening to see the inflationary costs with these parts over the past few years. I was looking at a thread from 2024 where someone mentioned that part and they stated it cost $23-24. It's now $38.99! And in my other thread on the solid state IVR - my hard copy 2024 Tom's catalog lists them for $39.99. WH and Tom's now sell them for ~$57. Roughly a ~50% increase in the cost of those parts in 2 years!

Todd Z.

I think recently ALL of the Holley company stuff has skyrocketed in price.

It's ridiculous.

 

[davisjstone]

I had a heck of a time getting my 90 degree explorer thermostat to seal. I have an Eldelbrock Performer intake. I tried multiple gaskets and multiple thermostat housings. Four seasons 84884, Dorman 902-1003, Murray, Gates C034902 housing all had the same results.

I tried multiple gaskets (felpro & the ones that come with each thermostat) and also tired the gaskets with sealant on one side, and both sides. All resulted in a slight leak under pressure. I also tried the Mr. Gassket 737 G mentioned. It's a nice piece, but it leaked too.

Then I tired a 45 degree thermostat and everything sealed up nicely, no leaks with a FelPro and the 737G. Unfortunately the 45 housing is just too close to the belt with my explorer serp.

When looking at ALL of the multiple 90 thermostat housing I noticed that the bypass hole is much larger than the 45 degree housings. See the picture. I think the larger hole on the 90 housing creates a weak point where there is not enough surface area to seal. Not sure why these housing have a larger hole.

I eventually got it to seal using Permatex Water pump and Housing RTV sealant only (no gasket).

Hope this helps someone in the future.

 

[DirtDonk]

I wonder if the larger hole was designed on purpose, to fix some other issue that they thought was important. Only to create another!
Thanks for the comparison.

 

[ba123]

That's just the coolant bypass. No reason to make it THAT big and risk the sealing surface. I'd bet that's just an after market crappy design.

Some jackass prob designed the part and didn't even notice that was a sealing surface.

However, if it only leaks between those two point, that isn't going to cause any problems. The larger outer seal has plenty of surface.

 

[ntsqd]

I can tell you from experimenting with it that making that by-pass hole smaller than old school normal is not a good idea. Didn't really experiment with going larger so no idea how that might affect things.

 

[joshua]

I had a heck of a time getting my 90 degree explorer thermostat to seal. I have an Eldelbrock Performer intake. I tried multiple gaskets and multiple thermostat housings. Four seasons 84884, Dorman 902-1003, Murray, Gates C034902 housing all had the same results.

I tried multiple gaskets (felpro & the ones that come with each thermostat) and also tired the gaskets with sealant on one side, and both sides. All resulted in a slight leak under pressure. I also tried the Mr. Gassket 737 G mentioned. It's a nice piece, but it leaked too.

Then I tired a 45 degree thermostat and everything sealed up nicely, no leaks with a FelPro and the 737G. Unfortunately the 45 housing is just too close to the belt with my explorer serp.

When looking at ALL of the multiple 90 thermostat housing I noticed that the bypass hole is much larger than the 45 degree housings. See the picture. I think the larger hole on the 90 housing creates a weak point where there is not enough surface area to seal. Not sure why these housing have a larger hole.

I eventually got it to seal using Permatex Water pump and Housing RTV sealant only (no gasket).

Hope this helps someone in the future.
View attachment 964034

I sanded my housing flat on a piece of glass.

 

[mimmonen]

This thread may have helped me, thanks all. I put coolant in my new Blueprint engine 302 Bronco Editions hoping to fire it up. Leaked like a sieve at the housing. As I live i n Reno with Summit Racing close, I went and picked up the Mr Gasket 737G gasket for use with a Mr Gasket 4364 thermostat. My housing is Ford part #C30E-8594. Everything seam to fit perfect. I’ll post with the outcome probably Tuesday

 

[mimmonen]

This thread may have helped me, thanks all. I put coolant in my new Blueprint engine 302 Bronco Editions hoping to fire it up. Leaked like a sieve at the housing. As I live i n Reno with Summit Racing close, I went and picked up the Mr Gasket 737G gasket for use with a Mr Gasket 4364 thermostat. My housing is Ford part #C30E-8594. Everything seam to fit perfect. I’ll post with the outcome probably Tuesday

Installed today with no sealant, torqued to 10 ft-lbs and no leaks. I think the water neck worked good with the gasket and good flat surface on the intake manifold helped.

 

[ba123]

Thanks for letting us know!

I've definitely thought of getting that gasket and prob will next time around. Been thinking of trying a different tsat anyway.

 

[ntsqd]

How odd that a MrGasket part is the go-to these days. Very, very odd.

 

[ba123]

How odd that a MrGasket part is the go-to these days. Very, very odd.

Which part is odd? The fact that it's so pricey or the company? It's the Holley company and they do a lot of things well...although I do remember years ago MR Gasket being a kind of crap company. I bet before it was acquired by Holley though. Looks like they bought hem in 2015 maybe.

 

[ntsqd]

For decades MrGasket was informally known as "MrTrashket" and they were a mfg of last resort. I'd say that Holley does a few things well, some only well enough, and others not terribly well at all. I bet the founders of Earl's are spinning in their graves in agony. Accel had vastly superior product to Mallory when they were bought by MrTrashket (who already owned Mallory), and shortly after all of their products became re-branded inferior Mallory product. Granted, that was before Holley bought all of them, but they've not bothered to really look at the Accel products and bring back those that were most appropriate.