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G3GM 1973 to 1977 A-bodys. Chevelles, Monte Carlos, El Caminos, Laguna, 442, Cutlass, Malibu, GTO, LeMans, Century, Regal, Grand Am, Grand Prix, Sprint, Gran Sport, Can Am, Hurst-olds, and other 73-77 A-bodies


Thermostat housing bolts?

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Thermostat housing bolts? Empty Thermostat housing bolts?

Post by 77camino Thu Apr 12, 2018 6:58 pm

While starting up the El Camino over the winter I noticed that the housing is leaking. I’m going to replace the chrome one with a stock housing. The bolts also are not stock. Before I pull it, I want to go get a new housing and bolts. Anyone know what size and length the originals bolts are on the 305?
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Post by bracketchev1221 Fri Apr 13, 2018 3:20 am

They are 3/8" bolts. I don't know the lengths off hand, but if you have the thermostat housing, just get bolts that are about 3/8" longer than the housing.
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Post by Sinister Fri Apr 13, 2018 11:20 am

Sure it's not the hose?
Easy seal job at the housing.
No high pressure.
Lightly sand the two surfaces.
New gasket.
Coat the bolts with thread sealant.
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Post by 77camino Fri Apr 13, 2018 11:42 am

I’ve had the chrome housing on other engines as well and have always had problems with them leaking. The previous owner put this one on and I’ve left it alone, but now that’s it’s leaking I figured I would just replace it.
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Post by S3SS Sat Apr 14, 2018 6:02 am

Chrome housings all tend to leak no matter how much RTV/gasket you use. Chrome housings cheap offshore junk...Warped, porous, weak
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Post by Joe73 Sat Apr 14, 2018 6:59 am

I've had good luck with the Mr. Gasket 2661 chrome water neck.  It has an O ring but no issues.  The part number for replacement o rings is Mr. Gasket 2668.

If I'm using a stock type water neck I like to use the Fel Pro 2202 O ring gasket.  No leaks and very reusable.  Install it dry, no sealant.  I havent used sealant on a water neck in years.  Gasket it readily available at auto zone.

And either way, put sealant on your bolt threads.
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Post by Joe73 Sat Apr 14, 2018 7:43 am

https://www.ebay.com/itm/Mr-Gasket-2661-Water-Outlet-for-Chevrolet-Chevy-V8-1966-75/302678991270?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649

Good Deal.
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Post by Podor Sun Apr 15, 2018 6:52 am

I had a similar situation on my car when I bought it. I was in a rush and none of the parts stores had any cast iron housings so I went with the Mr Gasket one and it is leak free. I like the o-ring, but the intake has to be pit free and smooth. Like Joe said, RTV can actually cause more leaks.
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Post by 77camino Sun Apr 15, 2018 9:19 am

In a recent thread, kc77momte was looking for a vacuum switch that goes in the housing. Would my 305 have had this from the factory or was that a Monte only thing?
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Post by bigredlaguna Sun Apr 15, 2018 9:26 am

How can RTV cause a leak?
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Post by bigredlaguna Sun Apr 15, 2018 9:28 am

77camino wrote:In a recent thread, kc77momte was looking for a vacuum switch that goes in the housing. Would my 305 have had this from the factory or was that a Monte only thing?

It is very likely that you would have had that vacuum switch.
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Post by Joe73 Sun Apr 15, 2018 10:56 am

i didnt mention that rtv can cause leaks but I do know that rtv can leak if you dont let it set up as per the directions prior to installation. Especially when temps are cooler.
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Post by bigredlaguna Sun Apr 15, 2018 2:00 pm

Joe73 wrote:i didnt mention that rtv can cause leaks but I do know that rtv can leak if you dont let it set up as per the directions prior to installation.  Especially when temps are cooler.

Ok. I've never had a problem with rtv, but I do let it tack up a bit before installing the gasket/part.
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Post by Podor Sun Apr 15, 2018 7:42 pm

bigredlaguna wrote:How can RTV cause a leak?

A lot of the time it causes the gasket to not sit flush or be "clamped" evenly. Most gaskets are designed to seal directly to the surface. RTV is used fill seams between two gaskets or where there is no gaskets. Some times it's a shade tree mechanic who uses it for insurance and didn't clean the surfaces or overtorqued it.
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