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Discussion Starter #1
I, um, "lost traction" in the rain the other day and my car started running real bad. Don't know if I hit the rev limiter or not since I had the radio on and didn't notice that I had lost traction.

During trouble-shooting, I found that #7 cylinder had no compression. I then put a tablespoon of 10w-40 in the cylinder and repeated the test; still no compression. I then double checked the fittings and cranked it again without changing anything and this time I got 100 psi.

I then repeated the compression test 3 times with the same results.
1. On first attempt without oil - no compression
2. On first attempt with oil - no compression
3. by just cranking the motor a second time after putting in the oil - 100psi (if I continue to relieve the pressure and crank again press drops to 90 then 40 then back to zero.

I know that normally if you put in oil and the pressure goes up, its the rings. But, this takes 2 attempts to build pressure.

Since it takes 2 attempts to get pressure after adding oil to the cylinder, I'm not sure how to interpret the results.

Is the oil getting worked around the rings or plugging something in the heads (worn valve guide) or maybe the head gasket?

HELP!

thanks
rob
 

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That is weird. :confused:

I would let it sit for a day and then do the compression check again. Just to verify your readings.

The only thing that I can think of is that maybe you had some carbon stuck in a valve seat that was letting a valve stay open. Then if cleared itself and is ok. When it wasn't making pressure, did you hear where it was escaping (intake, crankcase, exhaust, etc.)?

Even with shot rings, you should have had some compression. No compression is usually an indication of burned valve, or holed (badly) piston (IMHO).

But it seems like you’re on the right track. Do a cylinder leakage test. It’s a lot better than just the compression test. It will tell you condition of everything in the chamber. :thumbsup:
 

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Hmmmm, that one sounds a little strange.

It's NOT valve guides...both valves are closed during the compression stroke and the guides are behind the valves.

It's NOT a broken valve or else there wouldn't be any compression at any time.

I'm not sure if hitting the rev limiter would cause a compression loss entirely of itself. It sounds like either a valve seat or valve face might have a bad spot in it, which probably wasn't caused by over revving but you never know. The only other thing I can think of is that maybe one of your rings (top maybe) broke or eroded and sometimes the pressure is contained by the second ring. Maybe one of the valves in that cylinder is slightly bent (which could possibly be caused by and over-rev).

I don't know how many times you have used a compression tester, but it might be suspect also, or the technique with which it's being used could be a factor.

How did the plug from that cylinder look?
 

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Discussion Starter #4
94 Daily:
I am going to do it again hopefully tonight. I thought of the carbon too, but as soon as the oil gets used up, the pressure goes back to zero. So if it's carbon, it's not being cleared. I don't know how to do a leak-down test. Can I do it with my compression gauge?

rustyul:
I have used the gauge many times, so I don't think it's me, and the other 7 cylinders measured in the normal range, so I don't suspect the gauge. Plus I could hold my finger over the spark plug hole while cranking (compression was that low). I did this to verify that I was getting the tester seated properly. The plug was wet with both gas and oil when I pulled it to do the test.

What's so weird is that after putting the oil in, something is sealing up, but only on the second time I crank it and not for very long. Every other time I've done this test, when it was rings, it pumped up on the first time after putting oil on top of the piston.

The engine had been running for a minute or 2 so wasn't completely warmed up. The outside temp was about 65 with a lite rain. I didn't drive into any puddles and all the piping and resonator are removed, so there's nothing in the fender. Other than running bad, there are no mechanical noises (ticking, tapping, or knocking).

What would cause a burned hole in the piston?

thanks
rob

thanks
rob
 

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That's interesting. :2huh:

I leak down test is really great.

Here’s a quick discussion I posted a while ago:
http://forums.tccoa.com/showthread.php?s=&threadid=700&highlight=leakdown+and+test

Make sure you lock the crank somehow (usually a belt wrapped around the balancer and tied off will suffice. There’s a proper tool, but I’ve never used one. If you don’t you will push the piston back into the cylinder, possibly backwards, which would be bad for the timing chains.

I’m a big fan of cylinder leakage tests since they tell you so much about a cylinder’s sealing capabilities.

You may have broken a ring or ring land, but what is weird is that it builds with the oil and then goes away.

Good luck!! :thumbsup:
 

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Discussion Starter #6
Well heck, sounds like the head has to come off no matter what. Since my compression gauge has a quick disconnect for an air compressor, do you think it would be OK to put #7 at DTC, lock the crank, and apply air press and listen like you said?

If it's the heads, any idea on the price of a regular valve job?
If it's the rings, 02 explorer hear I come.

thanks very very much
rob
 

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Discussion Starter #7
just finished some more testing.

Compression test;
still no compression on first crank
couldn't get any after adding oil this time????????

leak down test;
with #7 at DTC could feel air coming out the valve cover vent in a steady stream. could hear air through the dipstick, but it was pulsating.

let me know what you think it is

thanks rob
 

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That is not good news!! :(

Sorry to hear that!! :eek:

If you're getting the air through the valve cover hole and the dipstick, then there is something wrong with that cylinder. The things that could go wrong are only the rings and the piston.

If you have a lot of air definitely coming from the crankcase, I'd bet you cracked a piston ring land.

I think the next thing I would do is if you have any mechanic buddies, have them come over and do a double check. Just to make sure you aren't doing something wrong. I doubt you are, but like the old saying goes, two heads are better than one. Pulling an engine is always the last resort and there's nothing worse than pulling an engine only to find nothing wrong. (I'm speaking from experience. :leftright )

Hopefully some more people will give some second and third opinions on your symptoms. :)

Gook luck! And some good news: Now you have a legitimate excuse to upgrade to an Explorer engine. :thumbsup:
 

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Discussion Starter #9
I haven't had anyone else do the test, but I did it on #1 while I had the plug out to find DTC and it passed. I then rotated the crank until #7 was at DTC, applied pressure and it came out the valve cover. I then marked the crank and rotated 360 degrees to get it on the exhaust stroke, applied pressure and air came out the exhaust pipe. I did this to verify I was on the compression stroke.

thanks for the help, sure was expecting to get more than 161k out of it, but oh well.

rob
 

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Just for giggles , pop the valve cover, and check the valve spring, and the keeper/retainer bwefore you do anything expensive.... good luck
 

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Discussion Starter #11
thanks Leland :)
That was what I thought should be the next move. God I hope it's something simple like a spring (crosses all fingers, toes, arms, legs, and even eyes), but since the car still runs and isn't making any mechanical noise, I'm still driving it until I get my minivan out of the tranny shop (hopefully tomorrow). Probably won't get to work on it until the weekend. I'll keep you posted.

thanks to all who have responded
rob
 

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Discussion Starter #12
Just realized something today; my #7 cylinder is dead, plug has oil and gas on it, it smokes, i'm getting terrrible gas mileage, and my CEL hasn't come on yet!

Does this sound like a problem?

thanks
rob
 

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That definitely sounds "ungood" figure on taking it down till you can see the damage, and then figure out what has to be done ... vaklve cover 1st, then ....
 

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Discussion Starter #14
I'm sorry, I wasn't very specific leland. I meant does that sound like an O2 problem or something. With all that unburned fuel and oil and smoke, shouldn't I be getting a code. CEL bulb check good.

thanks
rob
 

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Gee, i just dont know, i certainly wouldnt drive it that way, and there are lotsa scenarios that could be causing this , and its just one of those things where bad things are happening, and you have to take a wrench to it to find out whats causeing this,,,,,It wont get better on its own and you could be damageing stuff every time it turns over...
 

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Discussion Starter #16
Well its seems that a screw got into the intake and at first held the intake valve open, which caused the cam follower (rocker arm) to fall off. During this process the screw finally made its way into the cylinder.

What would you do?




thanks
rob
 

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