Rear Crankshaft Seals 673/711

[vanscottbuilders]

What does anyone know about the lead seal used for the rear crankshaft seal

in the 673 and 711 engines? When did Mack stop using them?

How difficult are they to change, and is any special tooling required?

Also - what about the rubber replacement/upgrade seal? Same question -

any special tooling required?

I am well into the conversion of a 711 for use in my B-67, and I am changing all

of the parts from the original 673 that need changing to fit the short engine bay.

Part of that is the bellhousing. Seems like a good time to reseal the crankshaft,

although there is no significant leak evident.

Thanks,

Paul Van Scott

[theakerstwo]

The lead seal on the rear was not a seal but a dust seal only. It did not realy see oil because if you look the crank has a slinger made on the crank as were a normal seal would go. The slingler throws poil back and keeps it in the engine and the lead wire is onlt to keep out dust , roaches. bugs. When you see one dripping oil it is a sign of too much blow/by. I have seen them replaced at the dealer years ago and if the engine has too much blow/by it will keep on leaking. To replace it first thing is trans has to come out and i always pushed the new lead wire down in the grove in the retainer as much as i could then i would use a old wrist pin and roll it in but leave it sticking up some and the you dont trim none off for fit. You add some grease to it and force the retainer up over the crank and that will form the fit. I am sorry but i can not remenber the update but should.I am thinking there was no up date on that crank shaft.

[Mike]

The lead seal on the rear was not a seal but a dust seal only. It did not realy see oil because if you look the crank has a slinger made on the crank as were a normal seal would go. The slingler throws poil back and keeps it in the engine and the lead wire is onlt to keep out dust , roaches. bugs. When you see one dripping oil it is a sign of too much blow/by. I have seen them replaced at the dealer years ago and if the engine has too much blow/by it will keep on leaking. To replace it first thing is trans has to come out and i always pushed the new lead wire down in the grove in the retainer as much as i could then i would use a old wrist pin and roll it in but leave it sticking up some and the you dont trim none off for fit. You add some grease to it and force the retainer up over the crank and that will form the fit. I am sorry but i can not remenber the update but should.I am thinking there was no up date on that crank shaft.

Glenn,

Since you mentioned blow/by......what is the normal cause of blow/by ? I always figured it was because of an engine stopped up from too much carbon and the end results was a full rebuild. Would you enlighten us on the subject, please ?

Thank You

mike

[Rob]

Glenn,

Since you mentioned blow/by......what is the normal cause of blow/by ? I always figured it was because of an engine stopped up from too much carbon and the end results was a full rebuild. Would you enlighten us on the subject, please ?

Thank You

mike

Don't want to steal any thunder but blowby is anything that gets by seal of the piston rings to the cylinder walls and into the crankcase. You see this as oil vapor comming from a draft tube on the engine because the engine block below the area of compression has slight pressure above atmospheric. Another byproduct of this is lubrication oil being forced past seals/gaskets. Most times an engine also passes, or is "burning oil".

Rob

[Mike]

Don't want to steal any thunder but blowby is anything that gets by seal of the piston rings to the cylinder walls and into the crankcase. You see this as oil vapor comming from a draft tube on the engine because the engine block below the area of compression has slight pressure above atmospheric. Another byproduct of this is lubrication oil being forced past seals/gaskets. Most times an engine also passes, or is "burning oil".

Rob

Will an engine normally need new sleeves or pistons w/ rings ? I've made the mistake in having a machine shop knurel the guides before and will never do that again.

Thanks

mike

[Rob]

Will an engine normally need new sleeves or pistons w/ rings ? I've made the mistake in having a machine shop knurel the guides before and will never do that again.

Thanks

mike

Generally yes. It depends on the size and wear of the cylinder bore. Normally, a cylinder bore wears with a taper as the piston and rings are pulled and pushed with the cylinder growing larger at the bottom of the stroke than the top. On an inline engine the piston pin is centered through the side skirt of the piston. On a "V" type engine of 90 degrees, the piston pin is off centered about .060 towards the lower side of the piston and that is why there is a definate "forward" mark in the piston crown, or head. This is to offset, or slow the wear from the sliding of the piston and ring combination. Cylinder sleeves are usually not thick enough to take an overbore and are replaced to fit to original size. The lower piston skirts wear from slapping the cylinder bore and the ring grooves wear from the constant "hammering" the rings give them from containing the force of compression, and heat.

Knurling of valve guides is not a real good idea in my opinion. The knurl just displaces metal by threading a mandrel through a worn guide and rolls threads into it. You then run a reamer through the knurled guide to bring it to correct internal diameter. When said and done, you have about 1/3 the amount of material remaining to facilitate a seal to the valve shaft and it is not smooth like the original guide. They tend to not last long either wearing both the valve stem, and remaining guide on short order. I've see guys knurl the skirts on pistons too. It doesn't last either.

Rob

[theakerstwo]

Well said rob a knurl job is what it sounds like and years ago they would do car engines that way and in a few months the guides are bad again and there is a good place to get blow by on the guides. Dont forget a bad turbo and air compressor and air compressors is a common thing on a S 60 DD.

[Mike]

Well said rob a knurl job is what it sounds like and years ago they would do car engines that way and in a few months the guides are bad again and there is a good place to get blow by on the guides. Dont forget a bad turbo and air compressor and air compressors is a common thing on a S 60 DD.

Hi Glenn,

What are you saying about a bad air compressor ? I happen to have one on the B at this time. I'm 2 weeks away before my new garage is finished. The concrete floor has been down for 3 weeks this saturday and the structure is finished but am waiting for the metal to be delivered and crew to get back. I started the ole Mack tonight, ran it up and down the driveway. Starts up just fine, but the brakes will no longer hold air very long. But that will soon be another finished project.

mike

[theakerstwo]

Hi Glenn,

What are you saying about a bad air compressor ? I happen to have one on the B at this time. I'm 2 weeks away before my new garage is finished. The concrete floor has been down for 3 weeks this saturday and the structure is finished but am waiting for the metal to be delivered and crew to get back. I started the ole Mack tonight, ran it up and down the driveway. Starts up just fine, but the brakes will no longer hold air very long. But that will soon be another finished project.

mike

Some times the breather on a air compressore will get dirt in it and wear the compressore out and you can get some blow/by thru it like the bad rings on your engine. Not so bad on a mack because the compressor is not as big as other engines and dont turn as fast.