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.

 

[rScotty]

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

Good. Be sure to use no more than a 50/50 mix of ethylene glycol and water. If your climate is hot, use less glycol to the water. Either use a premix, or I used to buy a gallon of 100% ethylene glycol at the auto parts store and mix it with distilled water. You need to premix and shake it well before pouring it into the radiator. The reason for the distilled water is that you are also trying to keep the inside of the radiator and engine block as clean as possible from any kind of coating.

It's also important to keep a good seal between the radiator and fan shroud to make sure that the fan is pulling air through the fins rather than around from the side of the radiator.

Thermosiphon cooling works pretty well on the flat or going uphill. It suffers when working down slopes that are steep enough to put the radiator somewhat below the level of the engine. That's pretty steep and not usually a problem - especially since the engine is doing less work on a downhill slope. I did overheat mine once years ago when digging along a steep drainage ditch with the front loader. All alone and concentrating on the work.....the blast of steam through the whistle nearly caused me to soil my pants. Back on the level or pointing slightly uphill it cooled down quickly while idling...
rScotty

 

[omrebel]

We don't have many hills but I use it to mow straight down and back up my pond dam. It's pretty steep, I have to wear my seatbelt. I don't mow it all at once because it does run hot. I've always used 50/50 antifreeze/water though. It's a great mowing machine. After bending both my 10mm wrenches to get the right bend, I finally got the dynamo off. The gasket looks good-maybe it would be better to re-use? But I don't want to do it twice....

 

[rScotty]

We don't have many hills but I use it to mow straight down and back up my pond dam. It's pretty steep, I have to wear my seatbelt. I don't mow it all at once because it does run hot. I've always used 50/50 antifreeze/water though. It's a great mowing machine. After bending both my 10mm wrenches to get the right bend, I finally got the dynamo off. The gasket looks good-maybe it would be better to re-use? But I don't want to do it twice....

If the gasket looks good it's probably the original,and came off nicely because it didn't have any goo on it. No reason why not to re-use it as you are going to build it up with the red silicone anyway. There's an art to re-using gaskets, but it isn't difficult. If you do re-use it, take care to apply the silicone in a nice even layer and let it go ahead and cure a little longer so it has a rubbery surface.

Another gasket trick for re-using gaskets is to clean the metal mating surfaces well and apply a thin layer of grease to the metal. Then if the silicon of the gasket is allowed to cure to rubbery before installing, the grease will help the rubber of the silicon to slide into any minute imperfections and also serve as a barrier to adhesion so that next time you take it apart the gasket will be usable again.

When re-using gaskets, it's the bolt holes that tend to wear out before the gasket face itself does.

rScotty

 

[rScotty]

We don't have many hills but I use it to mow straight down and back up my pond dam. It's pretty steep, I have to wear my seatbelt. I don't mow it all at once because it does run hot. I've always used 50/50 antifreeze/water though. It's a great mowing machine. After bending both my 10mm wrenches to get the right bend, I finally got the dynamo off. The gasket looks good-maybe it would be better to re-use? But I don't want to do it twice....

That's interesting about the heating up when mowing. Does it run hot when going downhill? That's when the thermosiphon is least efficient.

You can help it run cooler by slightly reducing the amount of glycol. The real technical recommended percentage was always 40% glycol to 60% water.... that gives a noticible increase in cooling over a 50/50 mix while still protecting down to about -13 F. We just always said 50/50 because it was easier to measure for most folks.

Resist the impulse to run straight water.... eventually everyone who does forgets to change it in the Fall and the result is a cracked block. That's a much bigger problem than just running hot in the summer. Thermosiphon engines are designed to run a bit hot without damage. Glad to hear yours is doing well. Not sure I'd change much. Those were dandy tractors. Well-designed for intelligent owner maintenance and given that they would last a lifetime.
rScotty

 

[omrebel]

I mow forward going down the dam and mow in reverse back up, no place to turn around at the bottom of most of it. It only gets dry enough to mow 2 or 3 times a year so it's pretty tough mowing. I think that it's working pretty hard is one reason it gets hot. Also the fan was in the way whenever I blew the radiator out, I didn't realize how dirty it was until I removed it. It's clean now and I think it'll cool better.

The gasket came cleanly from the dynamo but is still stuck to the engine side. I'm was thinking I may do more damage by scraping it off, and maybe I could put a thin layer of silicone on it, let it cure. I do have a new gasket if that's a bad idea.