LouisvilleLT4

A little background, the cheap plastic seal inside my dipstick tube shattered and I've been doing without any type of seal for a while. When I get around to it I will cover a long section of the dipstick in silicone, thick enough to seal the tube.

Meanwhile, when checking up on some things I ran the engine up to redline, and quickly noticed the smoke that was billowing off my headers because they had gotten a big squirt of oil from the dipstick. The dipstick itself had been pushed out of the way by the handle, as the oil squirted out.

My question is, is it normal for oil to want to come out the dipstick tube, or is it a sign of a bigger problem?

VetBoy89II

Sounds like blow-by.

Had the same problem with mine. As a temporary fix to keep the car from catching on fire, I rigged a piece of air hose from the dipstick tube down to an overflow bottle under the headlight with a breather. Once I started losing 1 quart of oil per 100 miles of driving, I decided it was time to tear her down.

That was about a year ago and she is still sitting in the driveway halfway done. The last thing I feel like doing after working on cars all day is working on my own when I get home ... oh well ... someday I'll get around to it.

corvette1989bham

valve / ring blown out. Needs attention ASAP.

LouisvilleLT4

Crap, really? Compression was good when I checked it. 200 in all cylinders except 180 in #8.

CFI-EFI

That is an indication of either a blockage in your crank case breathing system and/or excessive blow by. Blow by can stem from several causes, as stated. Most require a tear down, and some a complete overhaul to correct. That compression test with "200 in all cylinders" is cause for concern. The cylinder with 180# is on the high side of normal. 200# makes me ask, why?", "How?".

RACE ON!!!

LouisvilleLT4

I replaced my PCV valve earlier this year, if it was a bad one or somehow the wrong type, could that be it? I'd rather try switching that out than do a rebuild.

Mojave

My car was doing this, and my dipstick also had the seal area broken. Replaced the dipstick and now it stays in place. A lot of blow by could still cause this, however.

Tom Piper

I suggest a leak-down test over the compression testing.


Tom Piper

Matt383

Also, have you done any mods to the engine?

(Heads, cam, higher compression, stroker, etc.)

How many miles are on it?


Matt383

Tom Piper

Something to think about.

I had a Lincoln Town Car that had a 5.0 engne with a serious oil consumption problem on number 8 cylinder (number 8 on a Ford 5.0 is the last cylinder on the driver's side).
It would oil foul the plug in about 20 miles of interstate highway driving.
Before the plug would foul, pulling a hill caused excessive (loud) ignition knock on one cylinder only.
If you cleaned the plug, around town, you never knew there was a problem.
Leak-down and compression tests showed no problems.

It took me awhile to find it, but the problem was an age-hardened rubber grommet that the PCV valve seats in -- less than $5.00 fixed it.

What was happening was, at highway speeds, because the Positive Crankcase Ventilation wasn't working, pressure would build up in the engine and blow the oil that pooled around the number 8 cylinder intake valve passed the valve seal and into the cylinder (number 8 cylinder on the driver's side of a Ford 5.0 engine has an intake valve as the last valve on that side, not like a Chevy small block that has exhaust valves as the last valve on both sides)
Because the engine is positioned in the vehicle so it slants downward toward the rear, the oil would pool around the last valve and the combination of crankcase pressure and intake vacuum could overcome the valve seal and suck oil into the cylinder.
Also, when pulling a hill, because excessive oil was being sucked into the number 8 cylinder, the oil was lowering the octane rating of the mixture for that one cylinder to the point it would have audible knock.

After replacing the PCV rubber grommet, all the problems went away permanently.
I had the vehicle for 80K miles after that and never had another problem.

So, don't overlook little things like a leaking grommet.

Tom Piper

LouisvilleLT4

I'll take another look at those grommets... I already had to replace the tube and grommet on the passenger side because over time they warped and came completely unplugged...

Once again I'll stress that my dipstick seal has been absent when this has happened. GM had to have put that seal there for some reason, right? Why would they anticipate oil wanting to come there during normal driving, if it was an indicator of serious engine damage? And again, this doesn't happen all the time, it happened once at redline. Are you all really sure that this oil squirting suggests engine damage, and is not somewhat expected at redline-level oil pressures with a missing dipstick seal?

Mojave

The oil in the oil pan not is NOT pressurized (or at least it shouldn't be). It is just sitting there. Any pressure is from blow-by (pressurized air that got past the rings).

If you don't agree, why don't you get a new dipstick and find out? Mine was only like $8 at the dealer.

CFI-EFI

You could hardly have the wrong PCV valve. The biggest difference in PCV valves is the shape, the configuration, to fit the engine and the connections present. For pressure to build in the crank case you would have to have a serious blockage in the breathing system. A simple lack of circulation wouldn't allow pressure to build.



The seal isn't there to prevent "oil wanting to come there during normal driving". The seal is there for the same reason there is a gasket on your oil fill cap and a grommet around your PCV valve and also the breather. It is to keep splashed oil and more so, vapors from exiting the crank case polluting the air and making a mess on your engine. Even without a gasket on the dipstick, there was enough pressure in the crank case to push the stick upward in the tube. Your words convey denial. You are trying to explain away and justify the problem as "normal". Face facts. It isn't. You have an excess crank case pressure problem. It is time to stop making excuses and time to start fixing.

RACE ON!!!

LouisvilleLT4

Well poop.

Learning how to do an engine rebuild right now would be hell on my schedule... my car will be 40 miles away from where I work and live the whole time.

On the other hand, this is a really positive thing because for the first time I will know for sure what condition my bottom end and heads are in, and can be more confident about that stuff in the future when diagnosing problems.

So in a way, I hope that I have to do a rebuild. But I still want to be absolutely sure that there is a problem that warrants it. If I could manage to repeat the dipstick squirting, this time making darn sure it's not coming out my oil cap or somewhere else, that would be a good thing. Also, if there are any more tests for internal engine damage, like this leak down test everyone keeps mentioning, those wouldn't hurt.

Lastly, I wouldn't want to do a rebuild until I am first able to solve this other problem that has been plaguing the car; some days the car will start and run fine, and others it will not start at all, cut out suddenly, and misfire. After a variety of inconclusive tests, I suspect something electronic is intermittently going into fault, and I would like to get a freeze frame of what my car is doing at those times to isolate the problem, and fix it before I begin this next endeavor of putting new piston rings on and such. The last thing I need is, during the break-in period, the car to misfire and cut out on me repeatedly.

So that's pretty much the situation I'm currently looking at.

TM-Z06

I had the same exact problem with my LT4 when the plastic piece on the dipstick broke off - it made quite a smoke show too. I got a new/used dipstick from vette2vette and the problems went away.

GeosFun

This issue is common in bracket drag cars at high RPM's. The usual low buck "fix" is to vent the engine pressure by having a hose, usually woven wire so it looks nice, attached and mounted thru the valve covers and attaching to the collector on each side. These cars still show excellent sealing in the combustion chambers (compression and leak down) but they still build up pressure at high RPM's even with the tube.

In the more hi-dollar drag race engines, you will see vaccuum pumps running off a pulley on the front of the engine to evacuate the crank case pressure.

This does not mean your engine is in serious trouble. But check compression and leak down anyway to be sure. I would think you would have oil consumption if the rings were bad. Maybe just do not go to "red line" so much

LouisvilleLT4

You mean a new/used dipstick tube?
edit- nevermind, the sealing piece apparently is meant to be part of the dipstick


Didn't they say the oil in the pan is not pressurized at any RPM? So which is it?

GeosFun

The rotating assembly creates pressure at high RPM. The crank case is not pressurized by any other means. That is why it is a hi-rpm issue only (that is, enough pressure to blow oil out the tube, blow the dip stick out of the tube, etc, or any other opening.)

CFI-EFI

Oil forced out of an oil cap is the same problem with the same cause. A leak down test IS a good idea.



That isn't correct. First, the oil in the oil pan is not pressurized. Only the oil in the oil passages, fed by the oil pump is pressurized. The crank shaft rotating and the pistons going up and down, create a lot of turbulence in the crank case, but no pressure. Pressure in the crank case is caused by combustion gases escaping past the piston rings. It isn't "oil pressure" in the crank case, it is AIR pressure, where it shouldn't be, in the presents of oil, that is forcing oil from the dipstick or oil fill cap.

RACE ON!!!

GeosFun

CFI, I think we are hanging up on the English language here, but saying the same thing. You are correct, it is air pressure caused by the pistons going up and down, blow by. This is part of the rotating assembly to my way of thinking.

My point is, the problem under discussion apparently happened at "Red line." So my comment is, there may be nothing wrong with this engine's combustion sealing, but it should be checked. Compression and leak down are simple tests. I would think there would be conspicuous oil consumptions if the rings were actually bad.

The race engines I am referring to seal just fine, but they still build up a lot of pressure at high RPM's.