horntj1

I put a new thermostat in the Gen 2 12 valve and can't seem to stop the housing from leaking. I have tried to stop the leaks with silicon and new gaskets. I cleaned the surfaces on both sides well and when i put it all back together i still get a leak from the t stat housing. I can't tell weather it's coming from the lifting lug side or the outside but either way it's still leaking.
Anyone got any tips.

edwinsmith

Have you checked the surfaces for flatness? Use a steel rule and a thin feeler gauge to see if the gauge will slip under the rule. Use a nice thick paper gasket and tighten the housing to specs but don't overtighten. Good luck.

torquefan

Stupid question, but is there any chance that the cylinder head gasket is leaking and running down to the area of the thermostat housing? That is the most common area for the head gasket to fail with an external coolant leak.

horntj1

thanks Ed. I checked the housing and lifting lug to be sure they are flat and smooth on some emery paper. There are no paper gaskets with the t stat. Just the rubber gaskets that fit in the same hole for the thermostat.

horntj1

its possible but has never been over heated. I can't imagine a cracked head gasket but it's possible. I'll check into it. I sure hope not I have had the old girl for 17 years. Hate to part with her now.

thrashingcows

I use RTV on either side of the lifting lug, even with the seal/gasket that is there. Never had any leaks doing it this way.

horntj1

thanks I'll try that when i get back home. I'll put it on both sides of the lifting lug.

1972RedNeck

I second the head gasket.

torquefan

It's not a huge deal, and very common. Have seen several 12 valves leak from that corner of the head. The replacement gasket has been upgraded a bit to prevent the issue from recurring.

Jim Lane

Are you using this gasket?

t-stat lift hook - Dodge Diesel - Diesel Truck Resource Forums
I would get a Gates or one from Cummins,
I have heard cheap generic ones leak.
Is the thermostat install correctly?

edwinsmith

I'm pretty sure you need the flat paper gasket. The rubber ring just keeps the T-Stat in position. The paper gasket keeps the coolant from leaking.

Edwin

mknittle

Before I pulled the head I would give it a try without the lift hook.

N. Besonderes

Not saying that it is the head gasket, but if you run these engines long enough, it will fail at that corner.
A blown head gasket is certainly no reason to put her out to pasture, though. Just don't put it off any longer than necessary, or it will corrode the mating surfaces betwixt the block and head untixt they will'nt seal.

-Niemand

deere country

Their is no paper gaskets used in the thermostat. If you still have a doubt I suggest looking in the parts book and try to find a part number for it.

maybe368

I agree, it has been a while, but I don't remember a gasket...Mark