I have searched and cannot find a clear answer on this. When changing the thermostat in a 4.9 do you seal the gasket to the housing with RTV or something? I have some Permatex Ultra Black and some Permatex Form-A-Gasket 2. It looks like the PO used Ptex Red the last time it was changed. I wanna get this right the first time.

 

Pull the housing, clean both mating surfaces THOROUGHLY and use a new gasket. The ones I get from car-quest has an adhesive on one side of the gasket to hold it in place while you re-install everything.

$.35 for the gasket IIRC.

No need for Permatex.

 

You could probably get by without RTVS but it's cheap insurance in my opinion. A very light film will do. +1 for clean and that includes "dry" meaning there shouldn't be any antifreeze on the sealing surface while you're assembling it.

 

make sure you clean the surfaces well. if not you run the risk of breaking the housing....Happened to me. I was a ******* and worked in a hurry LOL. Still have a leaking issue probably should tighten up the fitting that goes to the heater core hose a little more.

 

Using those gaskets with the adhesive has NEVER given me an issue...On both trucks, well over 50,000 miles with 0 RTV. Plus it's less to worry about being squeezed out on the inner side of the gasket and getting in the waterpump, etc.

Also no wait times for it to "Setup".

 

More power to you, it's still a free country so far

 

I also like a thin coating of RTV High Temp. In fact GM in the 70s I know didn't use gaskets for thermostats or intake manifolds they used RTV High Temp. In fact some of the SBC if you used the rubber end gaskets instead of RTV it would hold the manifold just thousands of an inch too high & the exhaust crossover in the manifold would leak exhaust gases into the valley pan area & in 15-20,000 miles you would have a flat lobe or two on the cam. People blamed the cams when it was improper installation of intake.
I'm an old mechanic that saw this more than once.
Craig

 

Thanks for the replies everyone. This forum has been a great help. Anyways I never even got to the thermostat because in the process of draining/flushing my cooling system I encountered some radiator issues. I used one of those Prestone Flush and Fill kits but instead of cutting my inlet hose I just pulled it from the engine and ran the other end of the T-fitting though a piece of garden hose attached to the engine. After the flush I went to drain the radiator via the petcock but only got a slow dribble even though I could still see fluid in the top of the radiator. After about 30 minutes there was less than an inch of water/coolant/debris in the bottom of the bucket so I gave up on that and refilled the system (getting very late and need the truck tomorrow). Do I have a plugged radiator? All hoses are hot after running to operating temp. What to do next? Buy a new radiator or is there a way to pull this one out and clean it? Thanks for any help.

 

The drain could be plugged is all. I think you can remove them.

Craig

 

The bottom of your radiator is full of sludge. You don't need a new radiator (unless it's beat up or something), but I'd take it to a shop and have new tanks put on, it will get cleaned in the process. The '94 and '96 in my sig have both blown tanks, and it's never at a very opportune time.

 

Is it hard to replace the tanks myself? I bought the truck to learn how to wrench and I would like to do as many repairs as I can myself. You are right about sludge being in there. The PO put some kind of Stop Leak in there and it's a sludgy brown mess all over the place.

 

Not IF you happen to own or have access to a radiator shop and/or radiator tools...

 

I hear ya, but I don't think this is one of those times. This is one of the few things we take to a shop. You'll get enough experience just pulling out and installing the radiator LOL

Now you could probably hose out the radiator after you have it out, and get it pretty clean, but just be aware those tanks are a weak spot and I would definitely have them changed if you're going to bother pulling the radiator.

 

If the p/o put that stop leak crap in it, then IMO opinion take it to the scrap dealer and buy yourself a new rad. When I got my truck, the rad started leaking on the passenger side. $190 for a brand spanking new Rad. She also runs coller now as the old one was full of crap.

Stop leak is a waste of money, and can cause WAY more problems then a small leak. It can clog up coolant passages, and cause overheating.

When I did my thermostat, I used a gasket and a thin film of RTV. It leaks from time to time, but I think it was a poor quality gasket. Its actually wicking out of the gasket, not leaking between. Got a slightly better gasket and will swap it out one of these days...

 

Yeah it has been running hotter than normal lately which is why I've been tinkering with the cooling system. Can a radiator place flush all that sludge out of my engine coolant passages? What's a fair price for that kind of service?