excessive blowby

[mucekok]

finally got some motivation to get my most recently acquired duece to run correctly. originally had to replace injection pump and suspected a mistake in timing was causing the engine to run at full throttle. after coming dangerously close to scrapping the truck i found the throttle stop on the outside of the pump to be way out of whack. to my surprise the pump was timed right and it now runs correctly, sort of... here's the problem now... the blowby coming out of the crankcase vent tube is terrible! engine seems to have decent power but may have a slight miss just above idle. i am suspecting a need for valve adjustment, but that shouldn't have anything to do with crankcase pressure. i have no idea of the history of the truck, but am suspecting that it may have been an "ether-baby" and compression is suffering. i have not done a compression check yet so i am wondering if anyone has come across something simple that i am overlooking.

 

[jimk]

mine had a blown head gasket.It's been OK since replacing it.JimK

 

[jwaller]

the book says to drive it 100 miles of something like that and recheck it. I'd try it and see what happens. maybe the rings are frozen and this would loosen them up.

 

[houdel]

Blowby out the breather is a sign of some sort or pressure getting into the crankcase. As Jwaller suggests, it may just be your piston rings frozen up from the engine sitting too long, a good long drive should loosen them up if this is the case. If you have a blown head gasket, I'd expect to see you loosing coolant and finding coolant in your engine oil.

A head gasket replacement is not an exceptionably easy fix, but something you can do in the back yard if need be. About the only special tools you will need are a 3/4" torque wrench and a crows foot wrench to tighten the head bolts. A winch or several extra hands to lift the cylinder heads out is a big plus, they are pretty heavy. I can loan you the crows foot wrench but I don't have a 3/4" torque wrench yet. The worst case scenario is bad rings or a scored cylinder wall. Try a compression test and a cylinder leak down test to see it that is your problem. I can also loan you the compression and cylinder leak down tester as well.

My truck has the ether start system, but I think the "ether baby" syndrome is just an urban (or "green machine") legend. But on the other hand, I don't think my ether start system is working right anyhow. Try the good, long hard drive suggestion first to see if that solves your problem and let us know how you make out. It is well documented that the multifuel engines slobber all over the place if they are not driven hard frequently. Good Luck, Lee

 

[m35a2cowner]

Blow-by

An old truck is going to have some blow-by. What you might also be seeing is a lot of condensation (lot of short trips) making its way out of the engine as it warms up. I would warm the engine up by driving it for a bit. I would then take an oil sample (kits at NAPA) I would then change the oil and drive it a bit and then observe the blow-by. Remember that this type of diesel engine is not like a regular car engine. There is no crankcase ventilator (burns crankcase emissions in engines - PCV Valve) other than a straight breather tube. Its going to have some blow-by! It the engine runs well and it doesn't consume coolant or a lot of oil just drive it and enjoy it. I have seen a lot of trucks with blow-by run up and down the highway every day. Have the oil sample analyzed for metals and coolant content. Drive the truck several thousand miles and take another sample. Look at the analysis and gage it against the type of driving you have been doing. If any questions ask a mechanic what he thinks. Have fun with your truck.

 

[mucekok]

RE: Blow-by

adjusted the valves today and replaced two injectors. think #6 is dead, as there is no change in running when i break the fuel line loose. doesn't have a flat cam lobe, rocker arms are rocking away... drove truck down the street, killed every local mosquito, and even broke 20mph once(downhill!). i was thinking a blown head gasket, but while running it with both rocker covers removed the blowby is near equal from the front of the engine to the rear. no water in oil or oil in water. i think its just plain worn out... will continue to let it run and see if something changes before i take the blue tip wrench to it...