You could carefully put something in the spark plug hole to follow the piston up on each cylinder. Once the piston starts going back down, you know you just passed TDC and need to back up just a bit. This isn’t precise but close enough considering the piston dwell time at the top of the stroke. Before testing, make sure both valves are closed by confirming you have valve lash.
What went wrong with the engine?
Ranger
#22
[quote=“FishMan” post=63029]Before testing, make sure both valves are closed by confirming you have valve lash.[/quote] That means once the piston is at TDC, give it’s rocker arm pair a bonk with your knuckes on the cam side to make sure that each one is pressed against the cam vs. pressed against it’s valve. Otherwise the rocker could be holding the valve open a tiny bit.
barkerdm
#23
What I do is find TDC for #1 by the markings on the pulley. The put a wrench on the pulley nut noting its location. The turning the engine 2 flats of the nut will be 120 deg and the next TDC for the next cylinder in the firing order. Go through the firing order and you can get all of them done in 2 revs of the crank.
turbo329is
#24
[quote=“BTM” post=63023]As far as the water in the oil, you may have cracked the head. These heads crack at the coolant passage between the rear cam journals. With the cooling system full, pressurize the cooling system to 15 psi and check that area of the head for a coolant leak.
For the bottom end, your going to have to pull the head and inspect the bore. You might also want to pull the pan and then pull a piston out for inspection.[/quote]
I think this would be the best suggestion. You’re testing leakdown and compression even though you know you have a bad head gasket or cracked head. If the HG is blown it should be fairly obvious. There could also be some water in the cylinders. It hard to get it all out just by pulling the plugs and cranking it.
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Ranger
#25
Well, I don’t want to get into a struggle over this. I’ve said my piece and saying it over again doesn’t make it more or less valid.
Reliable testing needs to be done now, before the head comes off. Testing for a good seal at the rings is pretty much impossible without the head.
Sure, the HG is probably toast, although a coolant system pressure tester from Harbor Freight could provide nice confirmation of that. This could also help confirm/deny a cracked head.
Another thing to worry about is whether or not the over-heat was severe enough to damage the rings. They could be toast and we wouldn’t know it. That pretty much requires a guess, based on no better info than the severity of the overheat. IMO since IIRC there wasn’t coolant loss, there should not be failed rings nor a cracked head.
I still say that there’s something wrong with either the compression #'s aor the leakdown #'s. And since a leakdown test is harder to get right, my vote is with those good compression test #'s. All it would take is for the sparkplugs to be a bit loose, and the leakdown #'s would be all wrong.
jlevie
#26
My 2 cents…
A blown head gasket is unlikely to affect compression or leak down numbers on all cylinders. Worn valves, worn cylinders, or bad rings tends to have a uniform affect on all cylinders, which is what we are seeing here.
Maybe I’m just lucky, but I’ve never experienced any problems in doing a leak down test. The places where one can have problems are leaks where the adapter fits into the spark plug hole or in getting each cylinder close to TDC on the compression stroke. It will suffice to rotate the engine so that both cam lobes are pointing down on the cylinder to be tested, just like when adjusting valves. The picky person can remove the harmonic balancer and mark it every 120 degrees. But it isn’t critical to be exactly at TDC. As long as both valves are closed the results will be valid.
donstevens
#27
[quote=“BTM” post=63023]As far as the water in the oil, you may have cracked the head. These heads crack at the coolant passage between the rear cam journals. With the cooling system full, pressurize the cooling system to 15 psi and check that area of the head for a coolant leak.
For the bottom end, your going to have to pull the head and inspect the bore. You might also want to pull the pan and then pull a piston out for inspection.[/quote]
This is also what I was thinking.
Anytime you have “Milkshake” water in oil situation you really need to be suspect of the bottom end. Even a fairly small amount of water in oil renders the lubricating properties of the oil effectively useless. If you did even one lap at race speed with milkshake oil I’d bet your con rod bearings are toast.
Plus, 20% leak down would make me do a rebuild.
You are going to have to take the head off to install a new gasket and inspect for cracks anyway. Why not go the rest of the way and do new rings and bearings? Also, this way, you know that you are getting all of the water out of the oil.
Clearwater Cylinder Head can do the magnuflux for you and my buddy Ralph at D’elegnance in Largo can do the bottom end. Call me for numbers.
Don
Ranger
#28
Irksome thread.
I find myself in violent disagreement with some of the folks trying to be helpful on your engine woes. I’m not much into conflict so I’m going to try to make this my last post.
Caveats: There’s lots of folks with more experience than I, and if a test or symptom fools you one can travel a long way down the wrong path. Also, sometimes wild shit happens….symptoms that are impossible, symptoms that go away on their own, problems found that never showed any symptoms, etc. So absolutely nothing is “for certain”.
What we know for sure right now is that water is mixing with the oil and (IIRC) that the engine overheat was not that severe. This mixing is either caused by a blown HG or a cracked head. Blown HG’s are common, but usually a cracked head is a result of an overheat, not a prime cause of failure in isolation. That is to say….the head just doesn’t crack because it’s old and tired. Therefore the most likely issue is a blown HG.
We can make a pretty good estimate of whether or not the head is cracked based on how severe the overheat was. Basically, as long as there was water circulating in the system, the head probably didn’t crack. If it did crack, it’s going to be near the rear of the head because that’s farthest from the coolant path between pump and coolant outlet in front of the head. In the end tho, this really doesn’t matter because the head is coming off anyways to replace the HG. When the head comes off just have a machine shop pressure test the head and do a dye test for cracks.
What does matter is the possibility that the rings have failed. This is also a matter of the severity of the overheat. Again, as long as coolant was circulating the rings should not have gotten hot enough to fail. If, based on your judgement call you don’t replace the rings, you accept risk. As far as I know there’s no way to inspect the rings for metallurgical failure. My leakdown and compression tests gave no hint that my rings were bad in #6. They’d been subject to a severe overheat when #5 lost coolant and the head cracked.
Worry about ring failure, not bearing failure. IMO a little bit of water getting into the oil for a relatively short duration is unlikely to cause bearing problems. It takes very little water to turn oil into milkshake. I think that getting a little bit of water in the oil would be similar to the visc loss when you get some gas in the oil due to leaky injectors, or the loss of visc due to molecular shearing of the long chain molecules in oil that should have been changed 6 months ago.
We’re getting all wrapped up into compression tests and leakdown tests, but I don’t know if that’s time well spent. I still say that it’s impossible for a good compression test to show every cylinder fine and a good leakdown test to show every cylinder bad. But in the end, it really doesn’t matter all that much. The only genuine unknown is whether or not the rings have been damaged. Everything else is going to get determined thru the normal process of replacing the HG and taking the head to a machine shop to be checked and “surfaced”.
Surfacing is like “decking” the head except very little material is removed. The intent is to create a surface of the right “roughness” for happy HG bonding.
If this is a high mileage bottom end, instead of accepting risk on the rings this might be a good opportunity to redo the bottom end. It would be painful to get it all back together and find you made the wrong call on the rings, or find towards the end of the year that oil pressure is dropping due to bearing wear.
HLamar
#29
Here is what I use to find TDC. It is very accurate and cheap, probably free if you look around the shop.