1985 Bobcat 743 skidsteer rear main blowing

[Marcus Wyatt]

Recently the front engine seal went out. It appeared to be normal wear and age. (no idea of the hours) Replaced it and one hour into work and the rear main popped. Loud enough that I thought it was a hydraulic line. Nope, rear main. Pulled engine and replaced it. Wear ring looked great. Ran it about 20 minutes just idling and then half throttle, constantly looking for leaks I may have caused pulling the engine. Revved it up to full throttle when I felt comfortable and POP goes the new one.
Possibly too much crank case pressure? I haven't checked the blow by but it didn't use oil in any significant amount. Did I overlook something? Is it just worn out? I really need this old beast going. I've had it 3 years and it's been a good one, other than normal, expected wear on an older machine. Thanks in advance.

 

[Coaldust]

That’s weird. Check the crankcase vent. I would expect the dipstick to blow out before a crank seal.

 

[Marcus Wyatt]

This is what the rear seal looked like when I pulled the engine.

That’s weird. Check the crankcase vent. I would expect the dipstick to blow out before a crank seal.

Yes sir, I decided to do that after reading up some but if this V1702 has a crankcase vent, I'm not aware of it. Also, I noticed the dipstick was loose a while back and put some tape on it, to make a better seal. Your comment gets me thinking.

Thanks for your input.

 

[Coaldust]

Holy cow! Shame on the mess.
The vent on a v1702 should be on the valve cover like this.

 

[Marcus Wyatt]

Holy cow! Shame on the mess.
The vent on a v1702 should be on the valve cover like this. View attachment 246738

Lol, thanks for this! There is a plug where mine should be! I was actually wondering today what originally went there. This is helpful. Not sure if it's my issue but I'll certainly look into this. Unfortunately I only have a pic of one side of the motor before I reinstalled it. Pulling the valve cover tomorrow.

 

[Coaldust]

If it’s plugged, you found the problem. Sounds like the dipstick tube was working as the vent. Then you sealed the dipstick and now seals are blowing. That sucks that you had to pull the engine. Bummer deal.

 

[Marcus Wyatt]

Th

If it’s plugged, you found the problem. Sounds like the dipstick tube was working as the vent. Then you sealed the dipstick and now seals are blowing. That sucks that you had to pull the engine. Bummer deal.[/QUOT

If it’s plugged, you found the problem. Sounds like the dipstick tube was working as the vent. Then you sealed the dipstick and now seals are blowing. That sucks that you had to pull the engine. Bummer deal.

 

[Marcus Wyatt]

Thanks for your help. I suspect that this is the problem but at least it's an easy fix. Pulling the engine is not too bad. Everything is cleaned up now and I put mostly new bolts back in everything. It will take 3 to 4 days to get a new seal anyway.
Again, big thanks for your help.