b7100 hst gasket question

[omrebel]

I'm replacing the dynamo (if I can ever get the lower center nut off, then back on), and the coolant comes out of the engine in the same housing. I'm using a new gasket and I really don't want to have to do it twice. Should I use gasket sealant (permatex High temp red) , or use no sealant-just the gasket? If you can't tell, I'm not much of a mechanic. Thanks

 

[Egon]

You have trouble with that behind everything bolt?? Bend a wrench and the problem is solved. If you were near I’d give you mine.

 

[Dave M7040]

I'm replacing the dynamo (if I can ever get the lower center nut off, then back on), and the coolant comes out of the engine in the same housing. I'm using a new gasket and I really don't want to have to do it twice. Should I use gasket sealant (permatex High temp red) , or use no sealant-just the gasket? If you can't tell, I'm not much of a mechanic. Thanks

Why are you replacing the dynamo? Hardly ever fail.

Dave M7040

 

[omrebel]

My fan quit turning and I reset the tension on the fan belt. It turned for 30 seconds and stopped again. I took the belt off and it makes a terrible grinding sound if you turn it by hand. Apparently the bearing is shot. As a side note, I live in a small town of 2500 and when I went to the dealer to pick up my new Dynamo, they had 2 of them, Someone else here ordered one the same time I did. Anyway, I just don't know if sealer is recommended on the gasket.

 

[omrebel]

You have trouble with that behind everything bolt?? Bend a wrench and the problem is solved. If you were near I’d give you mine.

Thanks. I'm pretty sure I can get it off, I'm more worried about getting that nut back on. My 67 year old fingers don't bend that well.

 

[rScotty]

I'm replacing the dynamo (if I can ever get the lower center nut off, then back on), and the coolant comes out of the engine in the same housing. I'm using a new gasket and I really don't want to have to do it twice. Should I use gasket sealant (permatex High temp red) , or use no sealant-just the gasket? If you can't tell, I'm not much of a mechanic. Thanks

Use the sealer on the gasket. Keep in mind that it isn't a glue, it's just a light coating on the gasket that is slightly rubbery so that it can fill in any scratches or irregularities on the metal mounting surfaces.

Here's how I do it: With my finger I lightly coat both sides of the gasket with your sealer. Permatex high temp red is as good as any and better than most. You can use it most everywhere. Yes, it is a silicon based sealer that cures to a rubbery solid. You can tell silicon by sharp almost citrus odor of the uncured sealer.

Smear it on both sides of the gasket but not too thick. About as thick as a coat of paint is right. Then hang the gasket on a nail in the shade and let the permatex cure for a bit - you want it to cure enough so that it is no longer slippery or wet or sticky. Probably half an hour to an hour is about right. Those are the tricks: keeping the sealer thin, on both sides, and letting it mostly cure before mounting.The perfect cured gasket coating still be soft when you put it on, but it would be skinned over enough so that it isn't sticky and couldn't be pushed around with a finder. Don't worry about it if it cures longer. It will still be rubbery for days, and that's really all that is needed. In fact, some would argue that the longer cure is even better.

Remember again that you aren't trying to glue the gasket in place, the purpose of the thin rubber coating is that it is a coating on the gasket rather than on the mounting surface. Being rubbery, it molds itself to fill in any scratches or irregularities in the mounting surfaces of the dynamo and engine. Now it is true that a really good factory gasket should do the exact same thing without needing any sealer, and when originally assembling an engine most manufacturers will just use a gasket and no sealer. But then they are working with brand new mounting surfaces everywhere.

Whereas by the time you take things apart and scrape those formerly pristine mounting surfaces to get them clean then it's pretty common that the mating surfaces get beat up a little - even if only microscopically. So a bit of sealer on the gasket makes for insurance against leaks. Applied properly, some sealer just makes it all work better.

In most tractors, cars, & truck engines there are only two places where you should not ever put any additonal sealing product on. One is the head gasket that goes between cylinder block and the head. There you do not want any interference with heat transfer.

The other place is when rebuilding any high pressure hydraulic pump or motor. Their clearances are so exact that even the small difference of a thickness of a coat of sealer could be a detriment. In both those places the gaskets should be used just as they are supplied.
good luck,
rScotty

 

[rScotty]

BTW, weren't some of the early B7100s cooled by thermosiphon circulation rather than via a water pump? If so, and if yours is one of those .... then you should study up on how that cooling system works. It is a little different from a pressurized system. Nobody today uses that thermosiphon system anymore, but there was nothing wrong with it. If kept clean and with the proper proportion of glycol/water it is a fine cooling system.
rScotty

 

[Dave M7040]

BTW, weren't some of the early B7100s cooled by thermosiphon circulation rather than via a water pump? If so, and if yours is one of those .... then you should study up on how that cooling system works. It is a little different from a pressurized system. Nobody today uses that thermosiphon system anymore, but there was nothing wrong with it. If kept clean and with the proper proportion of glycol/water it is a fine cooling system.
rScotty

All North American B7100's had no water pump. Thermosyphon.

Need to check whistle on end of radiator overflow hose. Make certain it is not plugged with mud. Hearing the whistle is the notice to the operator that things are getting too hot.

Dave M7040

 

[omrebel]

Use the sealer on the gasket. Keep in mind that it isn't a glue, it's just a light coating on the gasket that is slightly rubbery so that it can fill in any scratches or irregularities on the metal mounting surfaces.

Here's how I do it: With my finger I lightly coat both sides of the gasket with your sealer. Permatex high temp red is as good as any and better than most. You can use it most everywhere. Yes, it is a silicon based sealer that cures to a rubbery solid. You can tell silicon by sharp almost citrus odor of the uncured sealer.

Smear it on both sides of the gasket but not too thick. About as thick as a coat of paint is right. Then hang the gasket on a nail in the shade and let the permatex cure for a bit - you want it to cure enough so that it is no longer slippery or wet or sticky. Probably half an hour to an hour is about right. Those are the tricks: keeping the sealer thin, on both sides, and letting it mostly cure before mounting.The perfect cured gasket coating still be soft when you put it on, but it would be skinned over enough so that it isn't sticky and couldn't be pushed around with a finder. Don't worry about it if it cures longer. It will still be rubbery for days, and that's really all that is needed. In fact, some would argue that the longer cure is even better.

Remember again that you aren't trying to glue the gasket in place, the purpose of the thin rubber coating is that it is a coating on the gasket rather than on the mounting surface. Being rubbery, it molds itself to fill in any scratches or irregularities in the mounting surfaces of the dynamo and engine. Now it is true that a really good factory gasket should do the exact same thing without needing any sealer, and when originally assembling an engine most manufacturers will just use a gasket and no sealer. But then they are working with brand new mounting surfaces everywhere.

Whereas by the time you take things apart and scrape those formerly pristine mounting surfaces to get them clean then it's pretty common that the mating surfaces get beat up a little - even if only microscopically. So a bit of sealer on the gasket makes for insurance against leaks. Applied properly, some sealer just makes it all work better.

In most tractors, cars, & truck engines there are only two places where you should not ever put any additonal sealing product on. One is the head gasket that goes between cylinder block and the head. There you do not want any interference with heat transfer.

The other place is when rebuilding any high pressure hydraulic pump or motor. Their clearances are so exact that even the small difference of a thickness of a coat of sealer could be a detriment. In both those places the gaskets should be used just as they are supplied.
good luck,
rScotty

Thanks! That's what i needed to know.

 

[omrebel]

All North American B7100's had no water pump. Thermosyphon.

Need to check whistle on end of radiator overflow hose. Make certain it is not plugged with mud. Hearing the whistle is the notice to the operator that things are getting too hot.

Dave M7040

I cleaned my whistle, and while I had the radiator off I cleaned all the cooling fins.