Excessive Crankcase Pressure, Blowby ???

Dahoopd

Registered User
What am I missing besides a couple sliices short of a loaf.

My car has been sitting for what I assume is a blown motor. I have no idea what it may be. The problem started with oil and smoke coming from the vent on the drivers side. I know I wasnt suppose to put a breather on there and I did it anyway. Live and learn.

On my way home from work in January, I got on it pretty hard. In the process of shifting into third, the car made a loud pop and fell on its face and stalled. The car immediatley started overheating and I shut it off. After cooling down, I had to limp the car home 28 miles and pull over periodically so it wouldnt overheat.

The weird part is there is no water in the oil, smoke from the exhaust and the plugs are clean. Yet the car runs like its on 3 cylinders and blows mad oil and white smoke from the drivers breather.

I have gone through hell with this car and cant afford to pay someone 2k to rebuild the motor. Yet sitting out in the elements has caused all of the underhood work to turn in to an ugly nightmare and set in the depression.
 
You should have drained the oil. If it has water in it, then you blew either a head gasket, or an intake manifold gasket. At a minimum you need to pull the top off the motor, and you should probably pull the motor and have new bearings installed due to running the motor with coolant in the oil.

Lesson for us all. If you blow a gasket and are leaking coolant into the oil, you must stop running the motor and you should drain the oil as soon as possible, putting anything fresh in there. Engine coolant + oil +combustion gasses trapped in the oil creates an acidic compound which damaged engine bearings.
 
You should have drained the oil. If it has water in it, then you blew either a head gasket, or an intake manifold gasket. At a minimum you need to pull the top off the motor, and you should probably pull the motor and have new bearings installed due to running the motor with coolant in the oil.

Lesson for us all. If you blow a gasket and are leaking coolant into the oil, you must stop running the motor and you should drain the oil as soon as possible, putting anything fresh in there. Engine coolant + oil +combustion gasses trapped in the oil creates an acidic compound which damaged engine bearings.

Mike there wasnt any water in the oil. The plugs are clean and no white smoke from the exhaust. Everything is coming from the breather. I checked the PCV and its working and not stuck.

The only thing I can think of is running the car lean. I was running 10% on the stock pump.
 
Actually, water and oil in an engine tend to create margarine which is just as good at protecting journals and bearing surfaces from rusting as plain oil. Even if that had happened, it wouldn't have hurt the bearings or journals to sit for months or even years like that.

What you most likely did is broke or melted a piston. You'll need a rebuilt shortblock no matter what.
 
I am wondering if you have a cracked head, piston, or cylinder wall. I would try a compression test (done by cranking over the engine with the starter). But try turning the car over by hand before you use the starter. This is just in case the car has water in a cylinder. That might tell you something.

After that, you can do a cooling system pressure test. You will need some adapters and an air compressor for that. If it bleeds down and you don't see leaks external to the engine, then you probably have cracked a water jacket in the head or block.

If those turn up good, then you have at least a silver lining to look at.
 
In my experience this happens when you crack a cylinder wall, bust a piston etc.

Yes water and oil is ok..Water and antifreeze and oil just isnt.

Damian, go to autozone...borrow a compression tester...Its easy to use. and will tell you where your having an issue without taking it all apart. You screew it into plug opening. turn motor by hand and read number
 
are we forgetting to make sure the throttle is held/set to WOT for this test? Otherwise your numbers would be lower than you'd like makes fr a poor baseline. Also engines that are still warm too when testing make better PSI vs cold ones.

Lastly dont forget to disable spark and or fuel by disconnecting the DIS module on both the early and late models. The car WILL Start with one cylinder down!!!:rolleyes::eek: been there done that at WOT
 
Last edited:
Yes water and oil is ok..Water and antifreeze and oil just isnt.

I didn't suggest running the motor with antifreeze in the oil, just that it won't damage the bearings and journals from sitting that way.

crack a cylinder wall

If you crack a cylinder wall, you'll have plenty of white smoke of which he said he has had none. As I said, 90% sounds like a cracked or melted piston. I've seen where this doesn't result in block damage, but generally it will need at least an overbore to go with new pistons.
 
I didn't suggest running the motor with antifreeze in the oil, just that it won't damage the bearings and journals from sitting that way.



If you crack a cylinder wall, you'll have plenty of white smoke of which he said he has had none. As I said, 90% sounds like a cracked or melted piston. I've seen where this doesn't result in block damage, but generally it will need at least an overbore to go with new pistons.

Ive done both. Cracked one where thee was no smoke then cracked one where I smoked up the whole block. I used to use stock 5.0 shortblocks going through about two a year. Cracked piston ring land could be an issue as well but usually youll at least have an comming out your exhaust with a piston issue in my experiences. check that as well....But a compression test will tell you if you have a big issue rather quickly...And generally if you do have water or antifreeze in your oil..You probably have it in your cylinders and its probably not fully mixed...So a drain and a cylinder purge and spray down with wd40 is always a good idea
 
Ive done both. Cracked one where thee was no smoke then cracked one where I smoked up the whole block. I used to use stock 5.0 shortblocks going through about two a year.

You are talking about 5.0 junk, not 3.8's. You'll never crack a 3.8 where it doesn't water down the motor. 5.0's crack just from looking at them.
 
Just went through it

Hey dude,
I just went throught this less than 3 weeks ago on my wifes SC. I had excessive pressure in the crankcase that was showing up as puffs of white smoke coming out of the oil fill with the cap off, it was in perfect time with the engine, looked like a little freight train in the valve cover actually.

Anyway, Dave D had suggested it was a broken ring land or broken piston. After tearing it apart, I saw no signs of any damaged pistons at all until i went to start cleaning them up. It was then I noticed I had not 1 but 3 broken piston ring lands. The funny thing is the car actually ran about 95% strong and it very hard to tell anything was wrong with it.

Now this engine had about 155,000 miles on the clock so and I have taken it down the 1/4 mile several times and buried the speedometer once (1994, SC 145mph Speedo)

If your car runs really rough it could be like Dave also suggested a burnt hole in piston, been there done that twice as well, and in those instances the car ran like crap, but gave the same puffs of smoke out of the oil fill tube.
Definitely sound like a complete tear down and rebuild at any rate.

I had to go with .030 over pistons cause stockers are no longer available, but in the end this rebuilt engine runs so well, it is hard to believe.

Good Luck, just thought I would share some very recent history with mine that sounded similar to your situation.

Smitty
 
Back
Top