Well, that was short lived....(sigh)
- Thread starter zigg
- Start date
zigg
Full Access Member
Well, I tried a couple more things today.
Read a thread over at the "other" site that talked about a leakdown test to figure out if you have cavitation pinholes or not.
I put shop air to each of the cylinders(Piston at BDC both valves closed) to see if pressure in the cylinders would cause bubbling in the coolant. None of them did. Each cylinder held pressure nicely, with only a hint leaking into the crank area(slight hissing up outa the oilfill opening) No bubbling, no rise in pressure at all in the coolant system.
I then tried pulling one glowplug at a time, and running it without a cylinder firing, one at a time, to see if I could isolate which cylinder was putting pressure into the coolant. Still nothing. Didn't matter which cylinder I had disconnected, the bubbling continued.
My guess is, it's a valve seat crack. It only leaks when the valve opens. I visualize just as the exhaust opens, the pressure quickly released from the cylinder pops the pressure up in the exhaust port for just a sec, but long enough to put just a puff of air through the crack. The rest of the time, when the valve is closed, the crack is not exposed to any pressure. This would explain why when I left the coolant system pressurized for over 6 hours, the engine didn't hydrolock, and pressure in the cylinder statically doesn't cause bubbling in the coolant.
So, I've pretty much resigned myself to pulling the heads. I just was hoping to narrow it down to one or the other, and at least figure out which cylinder was culprit. I guess one good thing has come of it though, in that if I had somehow botched up the head gasket when I put it on, it would have revealed itself in the leakdown test.
I really hate the thought of pulling the heads, that were tested prior to install, to find nothing wrong. Obviously my biggest worry would be to put it all back together, and then have the same thing happen.
Before I finally pull the heads though, I'll pull the thermostat, and see if I can make any sense of it, and obviously test it in a pot of boiling water.
This just isn't any fun at all...
Zigg
Read a thread over at the "other" site that talked about a leakdown test to figure out if you have cavitation pinholes or not.
I put shop air to each of the cylinders(Piston at BDC both valves closed) to see if pressure in the cylinders would cause bubbling in the coolant. None of them did. Each cylinder held pressure nicely, with only a hint leaking into the crank area(slight hissing up outa the oilfill opening) No bubbling, no rise in pressure at all in the coolant system.
I then tried pulling one glowplug at a time, and running it without a cylinder firing, one at a time, to see if I could isolate which cylinder was putting pressure into the coolant. Still nothing. Didn't matter which cylinder I had disconnected, the bubbling continued.
My guess is, it's a valve seat crack. It only leaks when the valve opens. I visualize just as the exhaust opens, the pressure quickly released from the cylinder pops the pressure up in the exhaust port for just a sec, but long enough to put just a puff of air through the crack. The rest of the time, when the valve is closed, the crack is not exposed to any pressure. This would explain why when I left the coolant system pressurized for over 6 hours, the engine didn't hydrolock, and pressure in the cylinder statically doesn't cause bubbling in the coolant.
So, I've pretty much resigned myself to pulling the heads. I just was hoping to narrow it down to one or the other, and at least figure out which cylinder was culprit. I guess one good thing has come of it though, in that if I had somehow botched up the head gasket when I put it on, it would have revealed itself in the leakdown test.
I really hate the thought of pulling the heads, that were tested prior to install, to find nothing wrong. Obviously my biggest worry would be to put it all back together, and then have the same thing happen.
Before I finally pull the heads though, I'll pull the thermostat, and see if I can make any sense of it, and obviously test it in a pot of boiling water.
This just isn't any fun at all...
Zigg
Darrin Tosh
IDI Hound
Bummer Zigg, I feel for you, You think you have all of your bases covered, just to go back and do it all over again.
That sucks,....
That sucks,....
zigg
Full Access Member
Well, I made an attempt at that Mel, but the problem is getting the enging to stay still while you pressurize the exhaust. The exhaust valve is only open when the piston is halfway up/down, and as soon as I put pressure to it, it pushes the piston back down till the valve closes.
Either way, looks like it has to come apart anyway...
(sigh)
Zigg
f-two-fiddy
Registered User
Dang Zigg, It sounds like you've about tried everything. That sux.
Who did the heads?
Who did the heads?
zigg
Full Access Member
I tried one last attempt today. To confirm that I was actually pressurizing the cylinders accurately, I pulled the valve cover on the Drivers' side, and undid all the rockers, so all the valves will remain closed on that side.
I re-did the leakdown test on each cylinder. Interesting results.
I mounted a hose in the hole for the glowplug controller at the back of the head so the top of the hose was 6" higher than the rad. Let the pressure equalize completely, filled the rad right exactly to top, rad cap securely on, marked the level of coolant in the hose, and left the top of the hose open so that air could escape, and any pressure in the coolant would push the level up in the hose.
Shop air (100psi) to each cylinder via glowplug hole one at a time.
#2, pushed coolant up the hose about 1" in 5 minutes.!!
#4, pushed coolant up the hose about 3" in 5 minutes.!!
#8, pushed coolant up the hose about 1" in 5 minutes.!!
#6, no coolant rise at all in the hose after 10 minutes!!
I did each cylinder twice to be sure.
***?!!
If my knowledge is correct, there should not ever be any rise in coolant pressure when the cylinder is pressurized. There shouldn't be any connection between the two!
Does this mean I don't have 1 crack somewhere, but 3?!!
It started to pour at that point, so I had to abandon ship, but I plan to do all those on the passenger side again just the same way, for comparison, and to rule out the passenger head.
I'll post results as they come in...
Finally, something is starting to make some sense, even if it still doesn't look good...
Zigg
I re-did the leakdown test on each cylinder. Interesting results.
I mounted a hose in the hole for the glowplug controller at the back of the head so the top of the hose was 6" higher than the rad. Let the pressure equalize completely, filled the rad right exactly to top, rad cap securely on, marked the level of coolant in the hose, and left the top of the hose open so that air could escape, and any pressure in the coolant would push the level up in the hose.
Shop air (100psi) to each cylinder via glowplug hole one at a time.
#2, pushed coolant up the hose about 1" in 5 minutes.!!
#4, pushed coolant up the hose about 3" in 5 minutes.!!
#8, pushed coolant up the hose about 1" in 5 minutes.!!
#6, no coolant rise at all in the hose after 10 minutes!!
I did each cylinder twice to be sure.
***?!!
If my knowledge is correct, there should not ever be any rise in coolant pressure when the cylinder is pressurized. There shouldn't be any connection between the two!
Does this mean I don't have 1 crack somewhere, but 3?!!
It started to pour at that point, so I had to abandon ship, but I plan to do all those on the passenger side again just the same way, for comparison, and to rule out the passenger head.
I'll post results as they come in...
Finally, something is starting to make some sense, even if it still doesn't look good...
Zigg
Most bizarre. 2 and 4 could make sense, but 8? Can you verify that you don't have presure building in adjacent cylinders? It almost sounds like the head has a crack and a strange grove running along the mating surface.
icanfixall
Official GMM hand model
Now its sounding like the head was not torqued down properly. Any chance you can check the torque wrench and try another torquing of that head. Just to see if thats what happened. If you have the rockers off along with the valve covers it may show you something. It sure would be better than pulling the heads only to find nothing and worrying about the reassembley.
zigg
Full Access Member
Well, actually, I double checked the torque with a second borrowed torque wrench(mine's a snap on), and went over the final sequence about 5 times when I was done, just to be sure I hadn't missed anything, so I doubt that's part of it, but one never knows. I probably haven't logged more than about 10 miles on the engine since it was first started up.
I suppose, at this point, it sure can't hurt to put a wrench on there again, and see if anything has changed, but I'd be sure skeptical about the torqueing figuring into it....
Zigg
You are using a recently certified torque wrench, aren't you? When I sent mine to TeamTorque.com, it was 10 pounds off. If I had used it to torque my head to 85 foot pounds, it would have been at 95.
f-two-fiddy
Registered User
It sure sounds like there's pressure moving from the cyl's to the cooling jackets.
It's gotta be the head gaskets. I can't see the heads/seats being that bad. Might be a warped head?
Again, who did the heads?
It's gotta be the head gaskets. I can't see the heads/seats being that bad. Might be a warped head?
Again, who did the heads?
zigg
Full Access Member
DAS in Vancouver/BC/Canada. These guys are diesel specialists, and do lots of 7.3/6.9's. They have a good reputation locally, and stand behind their work. At least, so they say, we shall soon see...
I tested the passenger side head today. Same pressure test, all valves closed, and all leaked, but especially #5, it pushed coolant up the hose 4 1/2" in 1 minute, and the piston was actually at TDC, not at the bottom of travel.
So, essentially, every cylinder when pressurized affects the pressure in the coolant to a greater or lesser extent. Just doesn't make any sense at all.
There just shouldn't be any connection between the two spaces at all.
I called Paul, at DAS, and talked with him about it, and he's at a loss. Says he's never seen anything like it in 20 years of working on diesels.
He's skeptical about the head studs. I can't imagine there could be any problem, but since it's every cylinder involved, there's gotta be a common denominator, I'm starting to worrry about that too. What if ARP sent me some that are just a bit too long? If I ran out of thread, then when I torqued the nuts, I might be tightening them, but not necessarily clamping the heads down any more. I might just pull one out, to see if there's any threads left, or if I've run out of thread on them.
I haven't pulled the heads yet, but prob'ly going to tackle it tomorrow morning and see if anything turns up.
(sigh)....
Thus the handle zigg(short for ziggy, the guy who has the little black cloud following him around, and everything that can, goes down the toilet...)
sle2115
NRA LIFE MEMBER
I would call ARP and ask for length specifications then measure the studs. Something just aint right. You could always take your old head bolts and replace the studs one at a time and try it again!
f-two-fiddy
Registered User
You are using a recently certified torque wrench, aren't you? When I sent mine to TeamTorque.com, it was 10 pounds off. If I had used it to torque my head to 85 foot pounds, it would have been at 95.
I concure, it's time to MAKE SURE the studs are torqued properly.
What was the procedure on installing them? Did DAS install them, or did you?
Did the engine come complete, then you removed the heads and installed studs?
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