Pcv valve issues

[i_ralley]

Couple things
I was having smoke coming from my engine and added a bypass hose to eliminate smoke isn’t the bus and it works.
Just had a mechanic look at my bus saying it sounds very healthy.
There is no pulsing, pressure or oil coming from my bypass hose just smoke.
Engine performs very well and starts instantly. He said the smoke did not smell suspect as in a sick engine.

We did notice somethings tonight;

1. My PCV valves are leaking smoke at the seam
2. Smoke is coming out of the dip stick tube but went away when the valves began to smoke more. Also smoke gone at higher rpm.


First question does the air compressor system share engine oil….. possibly creating pressure.

Can the pcv valves be assembled incorrectly my mechanic today was different than the one that serviced them.
Can they be removed without talking the doghouse off?

Trying to solve this issue I had excessive oil
Consumption switched to straight 40w and that seems be cured.

[Randy Dupree]

Yes,the compressor can charge the crankcase with air,simply remove the belt to test..

[i_ralley]

What’s the fix?
Some sort of check valve?

[Randy Dupree]

You have to know whats wrong before you fix it.
The compressor may be worn out,take the belt off,run the engine,watch for the smoke.

[Ssmarinediesel]

If you want to start at the PCV valves first, you’d be better off pulling the valve covers off to properly replace the PCV diaphragms. I was able to do it on mine without removing the doghouse, but mine might be a bit different than a normal FC since it’s an XV.

[tqwrench]

Originally Posted by Ssmarinediesel

If you want to start at the PCV valves first, you’d be better off pulling the valve covers off to properly replace the PCV diaphragms. I was able to do it on mine without removing the doghouse, but mine might be a bit different than a normal FC since it’s an XV.

I agree with Marcelino here, it can be done in chassis, but the bottom doghouse cover should be removed. If it's pressurizing the crankcase, it's a good time to invest in valve cover gaskets too. They seem to like to split after some time in service (not sure how long). The Cat house should have all the maintenance parts you need. I would suggest new hoses (if not already done) PCV & valve cover gaskets, diaphragms, and filters (little circular scrubby pad looking things inside the cans). You may want to invest in new bolts between the valve cover and cans (PCV valves) since they are Loctited in place. You DO NOT want one of those falling out and going through the valve train. They're little bolts. You can clean them up and Loctite them yourself too (that's what I did). Torque value provided in shop manual (here in downloads section). Wash all the parts in Varsol (mineral spirits), blow dry, follow shop manual recommendations for disassembly and reassembly. Pretty straightforward stuff.


If the valve covers are off, that's also a good time to adjust the valves.

[gspappa]

Originally Posted by tqwrench

I agree with Marcelino here, it can be done in chassis, but the bottom doghouse cover should be removed. If it's pressurizing the crankcase, it's a good time to invest in valve cover gaskets too. They seem to like to split after some time in service (not sure how long). The Cat house should have all the maintenance parts you need. I would suggest new hoses (if not already done) PCV & valve cover gaskets, diaphragms, and filters (little circular scrubby pad looking things inside the cans). You may want to invest in new bolts between the valve cover and cans (PCV valves) since they are Loctited in place. You DO NOT want one of those falling out and going through the valve train. They're little bolts. You can clean them up and Loctite them yourself too (that's what I did). Torque value provided in shop manual (here in downloads section). Wash all the parts in Varsol (mineral spirits), blow dry, follow shop manual recommendations for disassembly and reassembly. Pretty straightforward stuff.


If the valve covers are off, that's also a good time to adjust the valves.

All correct and good advice. We just worked our way through all that stuff on the 79. I would bring your Cat service manual with you when you try to order those replacement parts on the PCV canister. We bought a brand new one only because we couldn't get the parts and we believe we had some parts missing on ours which we did. So we played it safe. You can access that PCV canister from the passenger side of the doghouse down low to change out the diaphragm and the filter. If you want to change on the bench you have to remove the valve covers which might be a good idea too as already mentioned. Do the valves too! Check the compressor around the shaft for leaks and there is also a filter housing on it that can be cleaned. For $75 you can replace the governor while you are down there unless you know it's not the original or you have replaced it recently. We replaced our compressor (CAT #OR2903) figuring 42 years was a good run... I would think about it as the core is $1000+ at most suppliers if it is good.


Good luck!
We'll follow your post!

[i_ralley]

Tonight as a test I Pried the hose off the exit side of the PCV valve.
This is the driver side valve and started the bus there was zero smoke coming out of the end but there was smoke coming out of the seam of the PCV valve.

So has anyone done this? Should it smoke right away or under load?
I think I may have found the issue.



My valves where adjusted last winter and the mechanic cleaned the pcv valves.
I am wondering if he may have put them back together wrong or if the parts are just worn out.

[Mike Hohnstein]

https://c1.a2109.com/cat2/g0/g005/g00591490.png

[tqwrench]

Originally Posted by i_ralley

Tonight as a test I Pried the hose off the exit side of the PCV valve.
This is the driver side valve and started the bus there was zero smoke coming out of the end but there was smoke coming out of the seam of the PCV valve.

So has anyone done this? Should it smoke right away or under load?
I think I may have found the issue.



My valves where adjusted last winter and the mechanic cleaned the pcv valves.
I am wondering if he may have put them back together wrong or if the parts are just worn out.

A diesel makes the most normal blow by at idle. Pistons are moving slower, more time for gases to escape around the rings. Low speed/smaller explosions/less force on the rings to the walls and so forth.

I think it's time to crack the can open and see what's going on inside. Maybe the diaphragm ruptured or some hard part broke. I don't know, but would like to see what you find.