Richard Gallant, thanks for that! Looks like the .002 is correct. I'm gonna guess that's the same for the block. For aluminum heads, I usually just send them to a head shop and have them cleaned and the valves seated. If they are warped, then the shop can plane 'em down (if within specs). This truck has about 100k miles on it and I'm pretty sure the heads have been off before. I found a number of missing fasteners when taking it apart and one of the lower intake bolts was extremely loose. It wasn't stripped, so whoever did the heads last time probably forgot to torque that one. Also, I had to replace the radiator as it was full of Bars-Leak... they probably tried that at some point as a repair.

 

.0015 (I left a significant digit out!)

 

Yeah. .015 would be pretty bad warpage.

 

@Troy_Less Bars Stop Leak a tool of the devil surely

 

Richard Gallant... Amen to "tool of the devil". Back in the old days when radiators and engines were simple and BIG, it worked okay. But now with smaller everything that stuff causes way more problems than it solves. The radiator I pulled out felt like it was still full... even after draining.

 

Okay... checked the heads and the block's deck and all look good. I couldn't find any warpage at all with the .002 feeler gauge. I then used a flashlight and a giant magnifying glass and looked at the heads, block, and old gaskets to see if there was any visible area where combustion gas could conceivably get into the coolant system. I couldn't find anything.

Reman engines are around $6,000, so that's not an option for my buddy. And in my mind, there is not a good argument for putting a 20yr old used engine in the truck. Seems to me it would be more sensible to just go buy another used Disco II that was running. So, the decision has to be made whether to gamble and spend the time (and money) putting the engine back together to see if the problem is gone.

Any advice from the good people on this forum?

Thanks!

 

Given your situation I would pressure test it and if the block passes the pressure test I would put it back together and go with it. I have currently have three personal truck all was over 215,000 Mi on them, all of that head gasket job at least once if not twice in their lives. These engines are amazingly durable if you keep them cool, it took me about 13 or 14 trucks before I realized the inline thermostat mod was the only way to go I know, sometimes I kick myself because I feel like I'm a slow learner but there are still lots a people on this forum that will tell you that a good quality OEM thermostat works just as well as the inline mod and that may be true for a short period Of time but eventually they all quit working properly.

 

Extinct... thanks for the insight! Any idea how much pressure they use to test the block? I could make a kit pretty easily as I have an old water pump and a tig welder, but I worry about blowing out the freeze plugs. As I understand it, there are two freeze plugs on the back of the block almost behind the flywheel. Those are pretty large, so their high surface area means it's more likely they'll be moved by pressurizing the block. I REALLY don't want to have to pull the transmission just to put those buggers back in. I would think they'd take 25 psi as some radiator caps go up that high, but is that enough to find a small crack? Since water molecules are larger than air molecules, I presume it'll be harder to push water through the crack than combustion gas. This could explain why this engine gets combustion gas in the coolant, but no coolant in the combustion chamber (or anywhere else for that matter).

I saw where a guy who had a similar problem pressurized each cylinder via the sparkplug with 120 psi and then waited until one cylinder produced bubbles in the coolant. Would have been good to know this before I pulled the heads off! Though I was almost certain this engine had a blown head gasket due to being way overheated several times... so probably would have pulled the heads anyway. It might be worth it to put the heads back on, torque them down and try pressurizing each cylinder... I could probably build a makeshift clear filler tube for just the heads so I could see if there were any bubbles. Then I wouldn't have to put the intake(s) and ALL THE OTHER STUFF back on to test the engine.

The idea of pressurizing the cylinder is really quite clever I think. The combustion chamber can handle around 1000 psi... so 120psi is nothing. And it'll only allow a tiny amount of air into the coolant channels of the heads... and as there's no cap on the system, whatever leaks will just bubble out so the pressure will never get a chance to build up. May make the valves whistle a bit, but that won't hurt anything.

Any thoughts on this?

Thanks!

 

Oh, and one of the first things I did on this truck was to replace that crappy thermostat. I put a needle valve with a clear hose in the vent plug so I could make sure the air was out of the system.

 

I routinely pressure test mine to 30 psi, about double operating pressure and have not blown a freeze plug. I also use a block heater and circulate coolant to get it hot but that is out of the truck. In your case air might be best and you can windex the block and look for bubbles.