Thermostat Gasket sealant???

[rsilva708]

I have a constant coolant leak, and seems to be comming from the thermostat housing. I have replaced the thermostat 3 times already do to them sticking open, and have always had the coolant leak. Should I be putting sealant on the seal, or should it be put in dry. What else in that area could be causing the leak? I seem to be loosing about a gallon every few days. It only leaks when the X sits overnight parked. It doesn't look to be mixing with the oil at all. I have cleaned to motor to try and get a clear path that the coolant is taking, and it seems to start at the top of the thermostat housing, and covers everything below, and the oil pan is completely covered.

Thanks

Bob

2000 XLT 4.0 OHV

 

[410Fortune]

You sure its not the waterpump?

Which engine do you have?

Silicoln goes between the metal housing and the intake manifold. A rubber O ring goes around the thermostat itself.

 

[rsilva708]

You sure its not the waterpump?

Which engine do you have?

Silicoln goes between the metal housing and the intake manifold. A rubber O ring goes around the thermostat itself.

The water pump was just replaced.
It is a 4.0 OHV 2000 XLT and has 60500 miles on it.

So you should have some sealant on the housing? Can I use some permetex or even some Indian head gasket sealer?

 

[410Fortune]

permatex blue or red will seal it up. Gasket maker wont make up the gap.

Also it is VERY common to strip the threads on the bolts, steel bolt into aluminum intake = strip.

 

[rsilva708]

Also, is there any reason I keep getting stuck thermostats? I have only had the X for a year, and have already gone through 3 of them. I have tried differant brands including Fords, and all have ended up sticking open. Is it time to flush the system, as it seems like there is always a bit of gunk on the stat when it comes out.

Thanks

 

[Runnin'OnEmpty]

Bob, I've not had much luck with the German-made Motorcraft thermostats. They tend to stick open for some reason. I'm running a Stant now with good results.

You might check the thermostat housing for a crack. It has a welded seam that might have broken loose. That's a very big leak for being just a gasket.......

ROE

 

[410Fortune]

I agree, a gallon every few days? YIKES!

 

[Rhett]

Whoa, I have always NOT used permatex around where the thermostat housing hooks up...and I've never had a leak there. Does a FSM call for sealant there? Am doing it all wrong???

 

[410Fortune]

OHV metal thermo housing gets a light coat of silicoln, yes.

 

[gijoecam]

I had a problem on the 93 Ranger I had.... the t-stat had shifted in the housing the first time I went to replace it. A couple of days later, I noticed a leak. Tightening the bolts didn't help.... I took the elbow off and discovered that when the thermostat shifted on reassembly, and I tightened down the bolts, I bent one of the ears on the housing. 10 minutes with a file and sander and the elbow was flat again, and it never leaked after that.

It's possible you bent the housing. Try pulling the elbow off and checking it for flatness. I used RTV with the gasket to seal mine back up.

-Joe

 

[SVO42]

I've had problems getting T-stat housings to seal, and I've found that the best method (in my experience!) is to NOT use a gasket and only use Permatex Thermostat Housing and Water Pump sealant. No leaks on three vehicles so far!

 

[410Fortune]

thats called silicoln isnt it? the OHV 4.0L has no gasket, stock.
I am not sure I have ever seen a thermostat housing with a gasket?? the O ring on the thermostat is typically enogh to seal it up, but not always.

Anytime you have a machined metal to machined metal flat surface, silicoln or thick tacky gasket material will work, or at least it always has for me.

 

[SVO42]

Clarification--the thermostat housings I did this with were two Mustangs and a Jeep Grand Wagoneer. Ford 2.3s (on my Mustangs, at least) DO use gaskets on the housing stock. And they suck. I'll be replacing the radiator and t-stat next weekend on my X and it'll be my first time doing that on a 4.0L.

 

[410Fortune]

On the 4.0L you are in for a real treat

the bottom bolt ont he passenger side CAN be a PITA to get in and out.
UNLESS you use the right tools.

I have found two different approaches, both work well.

One is to use a 10mm wrench from behind the alternator to access the bolt
the other is to grind down a 10mm 1/4" drive socket to make it as short as possible. then put a wobbly on the socket and a short extension on the wobbly.

BE CAREFUL it is VERY easy and VERY common to cross thread this bolt.
Patience is the key.
You can put a piece of cardboard down under your work area so when you DO drop the bolt (trying to get it back in) it will not fall down behind the crankshaft pulley

This will save you ALOT of frustration. Sometimes it goes like clockwork, usually not.

 

[SVO42]

Thanks again, man!

 

[Runnin'OnEmpty]

You can put a piece of cardboard down under your work area so when you DO drop the bolt (trying to get it back in) it will not fall down behind the crankshaft pulley

Great tip.

And you WILL drop the bolt.......

 

[Glacier991]

Yeah the thermostat does seem to plague some folks on here, including me. I went through several in short succession, the last one I bought (a STANT I believe) has been just fine.

And yeah on my 1st Gen, what a PITA. Almost easier methinks to just remove the GD tensioner.

 

[Rhett]

Yeah, I've lost more bolts down in there somehow, including one of the 8mm bolts for the TB splash shield. Maybe I'll find it one day if I am doing valve cover gaskets. haha

If I start getting leaks around the stat housing I'll know to use some silicone...
I just never have, and it's always worked out for me. But since I like to do things right I will next time. You know what they say, you can never be too safe, with girls or cars.

 

[SVO42]

Just wanted to say how things went for me. I replaced the radiator and t-stat this weekend. After I got the radiator and fan shroud out, I made it easier on myself and removed the serpentine belt and the idler pulley. With those out of the way, I was able to use a 10mm socket, extension, and U-joint to get at the t-stat housing bolts. Once I had them loose, I slowly got them out by hand and didn't drop them. Once I had everything back together, I flushed the system and filled it up. The last two days I've added a little more to get it topped off.

Having heat again (and much faster!) is great. The temp gauge actually gets into the "NORMAL" range now.

 

[410Fortune]

Nice and good work!