Leak Down Tester?

[Hudson]

Yes it could. I would imagine that you are on the intake stroke and not the compression stroke and the intake valve is open. You need TDC compression

Any easy way to find that? I stuck a screwdriver down into the spark plug hole, spun the crankshaft until the screwdriver moved up, and when it hit it's max and started to slightly recede, i pulled out the screwdriver, screwed in my tester, and pumped air into the cylinder.

Is that not the compression stroke?

[ame]http://www.youtube.com/watch?v=k2zK3SMcK6E[/ame]

[ct67_72]

Nope thats just TDC. If your on intake, turn it around until its back at TDC and you will be on compression. Make sure when you get to the top, if the piston starts to come back down to turn the engine back over the other way. If its not perfectly on tdc it will just push the piston down.
You will find that there is a few degrees of crankshaft rotation that dont move the piston. i try for the center of this.

[Hudson]

Pulling the valve cover now to see if i can see anything.

Will post up pictures when it's off.

[Hudson]

Looks like someone made a milkshake inside my valve cover.

I'm going to get a brighter light so i can get better pictures but this is all i have for the moment.

Any ideas? Would i be able to see a crack or what? I'm looking between cylinder 3&4 (that's the 3rd and 4th one back from the front, correct?) and i don't see anything.

I think there is a slight tint of green to the oil, but i can't tell. I'm going to continue attempting to find TDC and continue with the leak down test.

[ct67_72]

much easier to find compression stroke with the cover off. Both valve will be closed, then get it to TDC.

[Hudson]

much easier to find compression stroke with the cover off. Both valve will be closed, then get it to TDC.

Will do that now, and then i'm going to perform a compression test.

Lets say i have a crack in my head which doesn't seem too far out of the realm of possibility at this point.

What is the best replacement head to get while maintaining somewhat of a budget?

Also how do I tell if I actually have a cracked head? What's to say its not a bad head gasket?

I've been reading up and everyone says once you see white milky stuff, it's time to replace the engine. Do I need to do this, or can I just get away with a head? What's the determining factor?

I drained all the oil out and it looks perfect.

[ct67_72]

That doesn't look too bad. If all the oil was like a milkshake than that's a different story as it usually ends in bearing damage.
It's all in the valve cover because the water steams out of the oil and rises. I would think head gasket before the head. Once you finish checking and determine combustion pressure is getting into the coolant and remove the head. Send it to a machine shop to be checked, cleaned and surfaced. If its cracked they will let you know.

[Hudson]

That doesn't look too bad. If all the oil was like a milkshake than that's a different story as it usually ends in bearing damage.
It's all in the valve cover because the water steams out of the oil and rises. I would think head gasket before the head. Once you finish checking and determine combustion pressure is getting into the coolant and remove the head. Send it to a machine shop to be checked, cleaned and surfaced. If its cracked they will let you know.

Oil looks perfect. No milkshake effect, no nothing.

Alright sounds good. So do this in this order;

1. Do a compression test.
2. If cylinder has varied PSI than other cylinders - leak down test it.
3. Remove everything connected to head, and pull head.
4. Check head gasket. (I've never seen a bad head gasket. Will i be able to tell if it's shot by looking at it?)
5. Send head out to a machine shop to be checked, cleaned and surfaced.

Lets say it does have a crack in it.

What's the best replacement head for a 1999 4.0?

[ct67_72]

Oil looks perfect. No milkshake effect, no nothing.

Alright sounds good. So do this in this order;

1. Do a compression test.
2. If cylinder has varied PSI than other cylinders - leak down test it.
3. Remove everything connected to head, and pull head.
4. Check head gasket. (I've never seen a bad head gasket. Will i be able to tell if it's shot by looking at it?)
5. Send head out to a machine shop to be checked, cleaned and surfaced.

Lets say it does have a crack in it.

What's the best replacement head for a 1999 4.0?

Yeah, with a mild leak it probably wont affect compression much. I would just do the leakdown. Figure out which cylinder it is. Also pull all the plugs when you do it so you can check for crossleaks in the gasket.
when you determine which cylinder and pull the head look at the gasket around the coolant ports. If its been leaking you can usually see signs of it degraded in the area or coolant tracks across it.

[customcreationsllc]

remember TDC happens twice on a 4 stroke engine.

Just put some air into the cylinder like you are doing and crank it over with a wrench until it gets hard and hold the wrench then do your leak down. If the piston is at the top it is easier to hold in place but a breaker bar you should be able to hold 100psi.

You can always do this even easier with just a nipple attached to the spark plug skip the whole gauge. But it is nice with a gauge to compare cylinders.

Also get yourself a radiator pump with a gauge and watch the pressure go up. You will be there all day waiting for a bubble.


I do this test all the time to check head gaskets leaks a very good way in my opinion.
Some time the pressure doesn't leak until over 100 psi and you will never figure it out this way.


Compression test don't tell much at all.
Leak down is the way to go.
Head gasket blown out look for the metal sealing ring around the piston they will usually be bent or the gasket missing around one spot.

Some times they will also leak from piston to piston so very hard to figure out a leak down.

Good luck
~Justin

[ct67_72]

Some times they will also leak from piston to piston so very hard to figure out a leak down.

Good luck
~Justin

This is why I pull all the plugs. You can usually hear air leaking out of the next plug hole.
I also have a combustion gas tester. Makes it easy to detect combustion gas in the radiator.
Also sometimes you wont see bubbles in the coolant, but you can hear them.

[ct67_72]

oh, and be careful if you try and hold a cylinder not right on TDC. I have tried a couple times and had the crank whip around. Even with a breaker bar on it.

[Hudson]

Thanks for all the advice. I feel really dumb. I can't figure out for the life of me where the TDC compression stroke is.

Here is yet another video of me attempting to find it. I'm pretty sure i'm missing it yet again. Can someone explain how to tell where it is just by looking at the lifters?

[ame]http://www.youtube.com/watch?v=xs8S5lDlzSM[/ame]

Custom are you saying i should put pressure into the cylinder, and then begin turning the crank bolt and when it gets really hard to turn i've found compression TDC?

That actually makes more sense.

I bought a combustion leak tester, and it showed that there was no combustion gases in my coolant.

However there is a bunch of milky substance in my valve cover, and a hint of green to all the lifters. I think i can even see the crack. I'll try to get a picture of it.

[ct67_72]

Did you use the combustion gas tester with it running?
Also you have to find TDC like you did before, use the screw driver to find the piston on top. There should be a mark on the crank pulley/balancer also. If your on compression both valves will be closed.
Look for the mark on the pulley. If your lined up, and both valves are closed (rockers level) you are there.
Here are the marks on the crank. Not all cylinders will use it but no.1 will.
Use the screw driver and as it comes up look for the timing mark on the crank. Line the mark up on the pulley. Make sure both valves are closed. You should be there.

[ct67_72]

Also remember as the engine comes around, the intake will open first. If your turning it around and the intake rocker is down (valve open) you will be close to bottom dead center. As the piston comes back up it will be compressing. This is where you need to be. the rocker will come up and the valve will close. You then need to line up the crank mark or watch for the screw driver to be at its highest. Thats TDC compression. If you keep turning you will go past, the valves will stay closed as the piston comes down on the power stroke, then as it comes back up the exhaust valve will open, and the piston will come back to TDC on the exhaust, as you turn past the exhaust will close as the intake opens and your back where you started.