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Engine blow by- does it need a rebuild?

Old 01-23-2016, 05:22 PM
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Engine blow by- does it need a rebuild?

So on my current road trip, I am getting a lot of oil leaks, from the front cover, oil dipstick, and tappet cover. Lots as in a half gallon every 1-200 miles.

I searched on here and found the manometer test and made one up. At idle the water was sitting at 8 inches-(actual measurement of tube rise)- 10 inches at 2200rpm, 11 inches at 2500rpm and at 2800rpm it was at about 24 inches? My measure marks stopped at 18.

Am I correct in that I need to double those numbers?
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Old 01-23-2016, 10:23 PM
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Oh man, that sounds kinda bad. Nothing interesting with the puke bottle right? If it's plugged up or pinched it might make oil spew out in all kinds of creative places. Like if you re-routed it and something choked it off...

A $15 non-contact laser thermometer might tell you a little- if you have a dead cylinder the exhaust manifold will be cooler on that port.
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Old 01-23-2016, 10:29 PM
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You're not leaking oil on the drivers side are you? If so, your vacuum pump is likely leaking. That will cause both the oil leak and false high blowby.
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Old 01-23-2016, 11:00 PM
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Originally Posted by jrs_dodge_diesel View Post
You're not leaking oil on the drivers side are you? If so, your vacuum pump is likely leaking. That will cause both the oil leak and false high blowby.
Yes, mostly. How would it be leaking? Like pumping air into the crankcase? I don't even use it anymore. I got hydroboost brakes now and a small electric vacuum pump for the a/c controls.
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Old 01-24-2016, 01:38 PM
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Originally Posted by LanceD View Post
Yes, mostly. How would it be leaking? Like pumping air into the crankcase? I don't even use it anymore. I got hydroboost brakes now and a small electric vacuum pump for the a/c controls.
Is the vacuum port on your vacuum pump plugged off, or is it free to suck air in as it pumps? It needs to be plugged off, or the air that it sucks in will end up in the crankcase, acting like blow by.
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Old 01-24-2016, 01:53 PM
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Originally Posted by torquefan View Post
Is the vacuum port on your vacuum pump plugged off, or is it free to suck air in as it pumps? It needs to be plugged off, or the air that it sucks in will end up in the crankcase, acting like blow by.
I had a bolt stuck in the end of the suction hose to block it off. Maybe it fell out... I'll go check

Edit: hose is still plugged, could it be sucking air from somewhere else and pushing it into the engine through the front?

Last edited by LanceD; 01-24-2016 at 02:14 PM. Reason: Added
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Old 01-24-2016, 02:29 PM
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Here's some pics of my manometer tool in use.


engine off



idle




2200 rpm




2500 rpm




2800 rpm it shot up to about 24 inches and started dumping water out of the tube
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Old 01-24-2016, 09:07 PM
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Yep, the "exhaust" of the vacuum pump is into the crankcase. So if there is a vacuum leak the vacuum pump becomes more of an air pump and can make an otherwise healthy engine look it has bad blowby. And since the vacuum pump is driven by the accessory gear, increasing engine RPM, will also increase the speed of the vacuum pump, and you'll have more "blowby" at high RPM.

That you have an oil leak as well on the drivers side leads me to believe that the shaft seal has failed. It sits between the power steering and vacuum pump. It keeps air out and the oil in, and when it fails you get a double whammy. That little seal failed on my pump shaft, and the time it took rebuilding it, kept me out of the bracket drag racing while we were on Guam.

I got a good write up on the repair from back then too:
https://www.dieseltruckresource.com/...0/#post1180491

Once the vacuum pump is eliminated as the potential culprit of your blowby, and you still have high reading, then we can look at the engine internals.
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Old 01-24-2016, 10:06 PM
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Originally Posted by jrs_dodge_diesel View Post
Yep, the "exhaust" of the vacuum pump is into the crankcase. So if there is a vacuum leak the vacuum pump becomes more of an air pump and can make an otherwise healthy engine look it has bad blowby. And since the vacuum pump is driven by the accessory gear, increasing engine RPM, will also increase the speed of the vacuum pump, and you'll have more "blowby" at high RPM.

That you have an oil leak as well on the drivers side leads me to believe that the shaft seal has failed. It sits between the power steering and vacuum pump. It keeps air out and the oil in, and when it fails you get a double whammy. That little seal failed on my pump shaft, and the time it took rebuilding it, kept me out of the bracket drag racing while we were on Guam.

I got a good write up on the repair from back then too:
https://www.dieseltruckresource.com/...0/#post1180491

Once the vacuum pump is eliminated as the potential culprit of your blowby, and you still have high reading, then we can look at the engine internals.

Awesome! Thanks for the info!
I really don't want to do anything to that pump since I will be eventually replacing it and my power steering pump with a nice hydraulic gear pump.

Is there anything I can do for now? Maybe make some more vents from the crankcase? Like those vented valve covers or a little filter in place of my oil cap?
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Old 01-25-2016, 08:13 PM
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The vents may help. The thing that worries me is that you are making a lot of blowby while the engine is unloaded in park/neutral. If you do have a internal problem (like rings or valves), the increased cylinder pressures make a lot more blowby. If this is the case, you risk more damage, blown seals, and losing oil.
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Old 01-25-2016, 10:48 PM
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Originally Posted by jrs_dodge_diesel View Post
The vents may help. The thing that worries me is that you are making a lot of blowby while the engine is unloaded in park/neutral. If you do have a internal problem (like rings or valves), the increased cylinder pressures make a lot more blowby. If this is the case, you risk more damage, blown seals, and losing oil.
I'll give them a chance. I got two Cummins valve cover breathers on the way. Any other symptoms of blow By? Like fuel in the oil?
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Old 01-26-2016, 07:42 AM
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Originally Posted by LanceD View Post
I'll give them a chance. I got two Cummins valve cover breathers on the way. Any other symptoms of blow By? Like fuel in the oil?
Years ago I had almost this SAME issue on my old 95. A set of the good Cummins Valve cover breathers pretty much took care of it.

Yes, the blowby is high, but if it runs good, gets decent mileage, starts good....why worry about it?

Chris
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Old 01-26-2016, 03:48 PM
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Yes, fuel oil dilution and a heavier contaminate load in the oil are the big concerns here with high blowby. Get enough fuel in the oil and it will trash the bearings, and eventually ruin the entire engine. Diesel has nowhere near the lubrication properties of lube oil. Fuel oil dilution is a big concern with our ships, the large propulsion diesel engines and generators. Depending on the engine and configuration, the fuel/oil dilution is tested either daily, or every 4 hours when the engine is run. Something our engineers take seriously since an overhaul on a large engine can take several weeks.

The contaminate loading means your oil will not last as long between oil changes as it should. Are you doing any sort of oil analysis on a regular basis? If you are not, it would not hurt to send in a sample. An oil analysis will show if there is any sort of abnormal wear and help to pinpoint a problem.

I am keeping my fingers crossed and hoping this problem you have is just the vacuum pump.
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Old 01-26-2016, 10:59 PM
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Originally Posted by jrs_dodge_diesel View Post
Yes, fuel oil dilution and a heavier contaminate load in the oil are the big concerns here with high blowby. Get enough fuel in the oil and it will trash the bearings, and eventually ruin the entire engine. Diesel has nowhere near the lubrication properties of lube oil. Fuel oil dilution is a big concern with our ships, the large propulsion diesel engines and generators. Depending on the engine and configuration, the fuel/oil dilution is tested either daily, or every 4 hours when the engine is run. Something our engineers take seriously since an overhaul on a large engine can take several weeks.

The contaminate loading means your oil will not last as long between oil changes as it should. Are you doing any sort of oil analysis on a regular basis? If you are not, it would not hurt to send in a sample. An oil analysis will show if there is any sort of abnormal wear and help to pinpoint a problem.

I am keeping my fingers crossed and hoping this problem you have is just the vacuum pump.
I haven't, but I will start doing sampling
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Old 01-27-2016, 07:03 AM
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Blackstone Labs

Those are the guys that I send my oil samples to. They do a really good job. Reach out to them and they will send free sample bottles.
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