Engine/Transmission (1994 - 1998) oil cap blows off

[runningbird]

the cap were you add oil keeps blowing off on our 94, 325,000 miles. this started happening at the same time an exhaust brake was added. Any ideas?

 

[Snow man]

Check your crankcase vent,sounds liketoo much blowby or a plugged up breather.

 

[Howard Durand]

I don't know if this would make any difference but did you install heavy duty exhaust springs when the brake was added?

Actually it sounds like you are getting blowby past the pistons into the crankcase.

Probably should check the compression.

 

[runningbird]

no I have not changed the valve springs yet,as I was not sure if this would make things worse. If it makes any difference the truck runs great, good power but does use about 1qt of oil every 1k.

thanks for the idea's

 

[NIsaacs]

Jeez, how much pressure would it take to blow that thing off. I would think that much pressure would cause oil leaks on every gasket that seals oil. Do you have a rubber washer on it? If not, it might vibrate off. I guess you must have a washer on it, since when it blows off it probably gets lost. What are you doing with your truck when it blows off? I never heard of this one Are the threads good in the filler tube?





"NICK"

 

[runningbird]

the cap is rubber and it just presses in or on. it usualy is on the motor somewhere although this time it is gone. It seems like it comes off after I use the exhaust brake heavly. but not really sure of this as I am not under the hood daily.

 

[Jim Fulmer]

I'd be willing to bet your crankcase vent is plugged causing that issue, and maybe causing the oil consumption issue by blowing oil past the rings.



Jim

 

[runningbird]

well i'll check the crankcase vent can someone tell me where it's at? thanks

 

[Kernel]

The vent will be a tube located just above the front pumpkin on your 4 wheel drive on the drivers side. It will be the biggest tube (not to be confused with the drain from your fuel filter) that attaches to a fitting higher up on the side of the block.



Scott

 

[tp0d]

if you havent installed the 60# springs for a full-on exhaust brake, i`d adjust the brake down to 40-50% (or something), or you may damage some seals with all that back pressure. i`m no guru on exhaust brakes, but it seems too coincidental that this started happening after you installed the brake...



-j

 

[Extreme1]

The oil cap should be made of hard plastic and thread into the fill tube. It sounds like what is on your truck is something someone stuck on in a pinch, that is likely why it is falling off.



You really need to install the valve springs, the next problem you will have is the exhaust valve hitting the piston. Not cheap.

 

[NIsaacs]

M. Smith, what e-brake do you have? Most of them will work with standard valve springs if they are set for them. The back pressure should be set at about 35 psi for max rpm. I have always been leary of the heavy valve springs in the older Cummins engines. Over the years they have improved the cam and followers to hold up to the heavy springs. They have made the lobes wider and harder. The standard springs are good for about 130 retarding hp, while the heavy springs will bring that up to about 190 hp.



I doubt that your crankcase vent is plugged, there is not much to go wrong with them. If you are getting to much pressure, you are most likely producing more blow by volume than the breather is designed to exhaust. I would guess that you have some mechanical issues arising, like valve guides, pistons or rings, or cylinders scored. One quart of oil per 1000 miles of use is an indicator of some engine wear. However this is not what I would consider excessive. If the motor is running good I would run it.



Like Extreme1 said, you most likely have the wrong oil cap, the Cummins one should screw in to the fill spout. If it blows off you should hear it, maybe even see it as it blows through the hood :{ Just kidding





"NICK"

 

[Vaughn MacKenzie]

One thing to check is when the engine is fully warmed up, is how much oil vapor is coming from the oil fill hole when idling. At the same time see how much is coming from the blowby hose.



If you do a search there are a number of discussions about sudden increased blowby and oil usage after putting an exhaust brake on higher-mileage engines. I would like to put one on my truck but I'm not sure if I want to. If I do I will probably dial it down.



Vaughn

 

[DMC]

Reduce the maximum rpms in which you are using the exhaust brake at. Say if you have been using the brake at 25-2700, cut it back to no more than 2000 rpm.



When I used to drive class 8 trucks, I drove this one truck that had 687K on it and when I would use the exhaust brake up near max rpms, it would push the dipstick up in the tube, until it vented the crankcase. By the way the motor was overhauled soon after this condition was found. I noticed it was getting kind of noisy when I cranked it up when cold.



Like the other guys said check your crankcase breather, it could be clogged. If not, I'm afraid your in for an overhaul. When was the last time the valves were adjusted? Have you been using a K&N drop in filter?



Good Luck



Don