| Author |
Message |
Roy Strickland smokey
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, January 17, 2006 - 4:11 pm: | |
Hey everyone, I have found that the oil that has been bathing my rear bumper is blowing out of the dipstick hole. I tied a little strip of rag around it and guess what, no bumper bath. Good, this is the first real progress I've made. Now, that the oil can't get out of the dipstick hole, it is coming out of the coffee can shaped device built into the rearmost valve cover. Is this the crankcase vent that everyone talks about? The very top of it is removeable and has a aluminum tube attached that goes down by the bottom of the engine and ends. I am working hard on my oil leak and just need a little advice. It definately sounds like some sort of ventilation issue. What do you guys think? Thanks |
Jim Stewart (H3jim)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, January 17, 2006 - 4:57 pm: | |
I think you're getting a little bit of blow-by. Probably not serious at this point, but the only cure for that is to rebuild the engine. |
Sojourner (Jjimage)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, January 17, 2006 - 5:34 pm: | |
To determine ring-blow-by is one of three ways after warm up.
1) Simplest is hold brake while automatic trans in gear then throttle engine enough so it labor hard for no more than 5 seconds. Have someone watch crankcase vent outlet. Pouring smoke is bad rings or barely smoke is good rings. If it puffing not pouring then not all but one or more piston ring is bad.
2) Rear wheel dynamometer run under load and watch vent.
3) Leak-down test……more than 18% leakage is limit on most piston engine.
4) Otherwise have your local charter bus mechanic to check oil leak.
FWIW
Sojourn for Christ, Jerry |
Gus Causbie (Gusc)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, January 17, 2006 - 6:08 pm: | |
Roy,
I had the same problem on my 4104 w/671. I found that the dipstick tube nut at the bottom was leaking oil, not much but just enough to make a mess.
I removed the dipstick tube, cleaned the threads on the nut and block and that stopped the leak. Before I found this leak I thought it was coming out the top of the dipstick tube so I remover the dipstick and attached a rubber hose to the tube and routed it down low to the left side. I really didn't miss the dipstick because I just watched the oil pressure and when it got down near 30psi I added a half gallon of oil.
Now that I found the leak at the tube base I'm going to remove the hose and find out if any oil was leaking through the tube.. |
Sojourner (Jjimage)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, January 17, 2006 - 6:47 pm: | |
You quote…”I just watched the oil pressure and when it got down near 30psi I added a half gallon of oil”.
I have heard that story before.
Are you aware sucking mixture of air & oil to cause lower oil psi? Other word partial or foam lubricant thorough out bearing & pistons cooling. $$$$$ of parts is in process of failure.
Oil pressure gauge is supposed to indicate bearings & pump wear.
Even well use worn engine with lower oil psi than normal is better lube with no foam in bearing.
Never use oil pressure for level check…..chance is your engine life is already shorter than you expect.
FWIW
Sojourn for Christ, Jerry |
Dale Waller (Happycampersrus)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, January 17, 2006 - 9:46 pm: | |
Hey Roy,
What oil are you using?
What type coach? What engine is it?
Check the airbox drains to see if they are plugged or stopped up. If so that can cause excessive back pressure in the airbox and crankcase.
A compression check and leak down check is probably something you need to have done. That will tell you alot about the condition of your engine.
Dale |
Tom Caffrey (Pvcces)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, January 17, 2006 - 10:17 pm: | |
And one more tidbit; early stage blowby in a Detroit two stroke will blow into the airboxes, so it won't show up at the crankcase until the wear is pretty bad.
A 6-71 boat engine we had rebuilt because of low compression had no apparent blowby, but there were 6,000 hours on it with many of those hours run at 9 gallons per hour of fuel.
It's something to think about when you try to figure out the wear.
Dale, how does a plugged airbox drain raise the pressure in the airboxes and crankcase? I don't think that they pass more than a percent or so of the intake air.
If the valves that are installed on many of these engines' airbox drains are working right, they block the airflow as soon as the engine is taken above an idle, anyway.
For what it's worth.
Tom Caffrey PD4106-2576
Suncatcher
Ketchikan, Alaska |
Gus Causbie (Gusc)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, January 17, 2006 - 10:28 pm: | |
Well Jerry, just telling you what I did not what I advise. I doubt that low oil pressure indicates air in oil, that would cause erratic oil readings with the needle making large excursions. What I described was a steady indication of slightly above 30psi, don't think that was cause for alarm. This is actually what happened, not theory.
I have seen oil mixed with air in aircraft and believe me it is not a steady reading. When this happened I had to keep the aircraft level, every time I lowered the nose the oil press dropped out of sight so I just kept it level all the way to the airport.
Low oil usually results in higher oil temps and lower pressure, that is theory and probably what happened to mine since it was during hot weather.
I've been working with engines for more than 50 yrs and if I thought it was bad for the engine I wouldn't have done it.
Never say never. |
Dale Waller (Happycampersrus)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, January 17, 2006 - 11:44 pm: | |
Tom,
If it is a naturally aspirated engine most likely there isn't any check valves. That's why I asked what engine and coach we are talking about.
If the drains are plugged up the airbox will never unload unburnt fuel and trash oil etc. That trash will cause the liner ports to plug up and cause high air box pressure, then excessive blow by of the oil rings.
See Detroit Diesel Trouble shooting section 15.2 The first paragraph tells you that that clean air box air is used to create a slight pressure in the crankcase by air passing between the oil rings and liners to prevent the entrance of dust. If to much air box pressure it pressurizes the crankcase too much.
Dale |
Dale Waller (Happycampersrus)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, January 18, 2006 - 12:40 am: | |
DD trouble shooting section 15.2 under Crankcase Pressure there is a list things to look at.
This was just one check to perform to find the trouble. There is a whole list of stuff Roy can check, but some require special tools or taking the engine apart. I was trying to give him some stuff to he can look at in the driveway before a trip to a bus garage to spend $$$.
Also Roy you may look at the exhaust system for excessive back pressure. If a varmit built a house or you have mashed pipe that can cause High Crankcase Pressure problems
Dale |
Tom Caffrey (Pvcces)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, January 18, 2006 - 11:48 pm: | |
Dale, the following is still giving me trouble:
" That trash will cause the liner ports to plug up and cause high air box pressure, then excessive blow by of the oil rings."
I looked at the manual, and I don't see where it says this. I do see that it says partially plugged ports will cause high airbox pressure.
Have you had some experience with Detroits that caused plugged ports? I can see that if blow-by was bad that it might foul the ports, but I'm having trouble seeing this in a good engine.
Thanks.
Tom Caffrey PD4106-2576
Suncatcher
Ketchikan, Alaska |
Dale Waller (Happycampersrus)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, January 19, 2006 - 10:20 am: | |
Hey Tom,
I have had trouble with this. On our NEGLECTED log trucks with DD strokes the drivers just run them and don't check anything. "It ain't my job" mentalilty, so that had me thinking that on Roy's bus. Some of the stuff he had previously described on other post makes me think it was neglected big time.
I need to break down and get a digital camera and post some pics. I have some aluminum inspection port covers that I would love to show. The sludge is built up even with the gasket surface with 3/4" thick nasty stuff. Some of the trash is hard as a rock and then it gets built up around the ports with no other way to escape with the drains plugged. When it gets to the liner ports it kinda looks like it gets baked hard.
First one I seen ran me nuts with oil leaks. It had good power, ran great, started easy, but leaked oil out of the valve covers alot. I changed gaskets and covers. I pressure washed that engine I bet 20 times. An old timer showed me the liner ports and drains were plugged. I cleaned as much as I could and that stopped the problem.
I think that if the air box drains were checked regularly this wouldn't happen. The older guys I work with at the shop tell me that alot of idleing with clogged drains causes this. I would think that if not caught in time it could destroy a set of rings or worse.
Dale |
Tom Caffrey (Pvcces)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, January 19, 2006 - 8:56 pm: | |
Dale, thanks for the info. That helps me put it in perspective. I think that you're right that neglected engines can have a lot of problems.
Tom Caffrey PD4106-2576
Suncatcher
Ketchikan, Alaska |