robox

After finally getting the thermostat housing off, I saw that whoever was monkeying around with this area before me used a whole bunch of some kind of black sealant around the gasket and between the mounting surfaces of the housing and the engine.

Question: Is this right? Should I use some kind of sealant there? Or use nothing other than the "short tube" type gasket for the thermostat?

(P.S. I had to cut off the heads of the top two bolts holding the housing to the engine! They were that seized!!)

Jim Lane

Check this out.
Jim


https://www.dieseltruckresource.com/...6&postcount=10

dpuckett

I've never used sealant there, and I have done 2 of them with good luck. Just clean up your surfaces and put it all together.

Daniel

robox

Thanks fellas-

CR

Jschlachta

I just did mine a few weeks ago. was not a problem. just used the gasket. funny or scary thing was that the previous owner had put the thermostat in backwards. Wouldnever warm up fully. I guess the pump would just push open the thermostat.

robox

As I mentioned in another post (but sadly got no replies) I replaced the thermostat gasket, but still have a pretty aggressive leak. I think it might be coming from the head gasket right at that spot.

Anyone have any ideas about a temporary fix.... something other that pulling the head for a new gasket, which I don't have time for right now?

wannadiesel

Everything looked OK in the thermostat housing and bore? The fact that the last guy to work on the truck used some sort of dum-dum in there makes me think something is damaged and causing the leak. I don't think it's a head gasket issue. I'd take it apart again and look at everything closely.

robox

I see your logic, Dave. Believe me, Id rather it was a thermostat housing issue, rather than a head gasket issue.

Also, as I said earlier, in another post I think, I had a leak here before and took it to a mechanic. They fixed it, apparently with plenty of silicone, and it lasted OK for about a year. This also seems to suggest the problem is with the thermostat housing area.

I tried to get under there to see what was going on, but couldn't. So, I stuck my digital camera where my head wouldn't fit (not a bad trick for seeing in hard to access areas) and the results were..... inconclusive. Still really hard to tell... (Picture taken from below thermostat housing, horizontal line with antifreeze is head gasket level)



SO I took it all apart again and reassembled with Ultra Black RTV on the mating faces (therm housing, lift-ring plate, and head). Sometime tomorrow I'll re-torque and refill the radiator. If it's still coming out I think it must be the head gasket.

CR

Chrisreyn

what was the out come of this?.. I have developed a antifreeze , well too big for a "leak" , more of a hemorrage, just under the thermostat housing, cant tell if its coming from the thermostat or head gasket. I tried slipping my camera under there and couldnt get a decent picture. Theres white antifreeze stain all over the head gasket surface and the bottom of the thermostat housing.
It is only leaking under pressure( running , warm) and no haze or smoke...

Chrisreyn

What danger do i run to the engine by keeping the coolant full and running it this way for a few days until I get the parts in?

robox

Well, Chrisreyn, I don't have a really great answer for you, but here's the latest on my leak...

I reassembled the thermostat housing with black silicone on the mounting faces of the housing and the lift-point plate. After letting it cure, I refilled the system and had initially had no leaks, before starting the engine. I thought this was a good sign because the last time I had big leakage immediately.

However, after starting the engine, the leak was back, though not as bad as before. Out of frustration, I am driving it anyway, refilling it often.

I still don't really know where the leak is coming from, though I'm leaning toward the thermostat housing instead of the head gasket. I am considering disassembling again and machining grooves into the component mounting faces to accept O-rings....

I'd say you run little danger as long as your temp gauge doesn't spike, and you refill often. What parts are you waiting for?

CR

Chrisreyn

I dont have a Cummins shop close, so I am having to mail-order from teh shop in Wichita for the thermostat gaskets. Figure it will take about 3-4 days to get.

NAPA has the gaskets, but I have read on here to use the Cummins ones instead... guess theres a quality difference?

robox

Update on my stubborn thermostat gasket problem....

First, I replaced the "gasket" (really a seal) with a NAPA seal, without silicone. Result: Immediate massive leaking, even before engine was started.

Second, I disassembled and then reassembled using the same seal but this time using Ultra Black silicone. Result: no leak at first, then a decent sized leak after running truck a few minutes. I thought I could do better, so....

Third, I ordered the Cummins seal and installed that without silicone. Result: Again, immediate massive leaking, even before engine was started.

Fourth, disassembled and then reassembled using the Cummins seal and grey "water pump and thermostat" silicone. Result: Again, no leak at first, then a decent sized leak after running truck a few minutes.

Not surprisingly, I was pretty frustrated by this point, so I stopped by my mechanic. At his suggestion, I pulled the alternator, then he pressured up my cooling system and with a mirror definitively saw that it's coming from the head gasket.

So, I obviously have a problem with my thermostat seal which demands silicone, AND I have a coolant leak from the head gasket directly below the thermostat. FUN!

I guess I'll be reading about head gasket replacement to see if it's something I want to try to do myself.

If nothing else, maybe y'all will be amused by my travails.....

Chrisreyn

Mine has also started leakign again
I hope I dont have the same problem!!!!!!!!

dpuckett

Remove your hood, use a chain & come-along with one of your forklifts and have at it. It is a lot of parts, and you need a good torque wrench, but I wouldnt pay someone to do it. Budget 2 days if it is your first one. Get the head checked for cracks and flatness. I paid someone both times for that one. I left the manifold on the head the second time around, due to the tendency of bolts to break upon removal.

Get everything clean, clean, clean for the head gasket/ reinstall. I used a brass wire brush cup on a cordless drill to clean the block deck, then lacquer thinner to clean it all off. Use good lint free towels for this one. Change oil and antifreeze at this time, no matter how recently any of it got changed.

As long as you arent getting any fluids mixed, keep an eye on your coolant level and you'll be able to drive it a while.