Coolant System Pressurized When Cold

Discussion in 'Street/strip 400/430/455' started by accelr8, Sep 15, 2022.

  1. TrunkMonkey

    TrunkMonkey Well-Known Member

    Couple of things. (for anyone that may use Thermocure)

    You may get a "false positive" with the Thermocure in solution with the gas tester.

    I did, had to do a flush and fill with water on my nailhead after I put the car together and had used the Thermocure.
    Had high temps, and finally replaced the radiator, but during troubleshooting, I wanted to eliminate head gasket/cracks as a possibility and kept getting "positives" on gasses, so I did a drain/flush/fill with water and got several "good" readings, drove the car for a few weeks and tested again, still good, so I drained and did 50/50 antifreeze/water and it has been since that time and several years.

    Must be something in the Thermocure that causes a false positive. I know you can get a false if antifreeze enters the tester, but in my case, with the Thermocure, no liquid got into the tester.

    Another thing is to make sure if you get any Thermocure on chrome (bumper), rinse immediately.
    I had the upper radiator hose blow off (new clamp failed) and the coolant with the Thermocure sprayed all over the grill and bumper. I was able to get the hose back on and drove with the cap loose so not to build pressure and drove home.

    The coolant was in contact for about an hour before I was able to rinse it all off, and have a light discoloration on an area of the bumper where the solution pooled.
     
  2. accelr8

    accelr8 Well-Known Member

    Good to know, Michael. I was planning to test the water/Thermocure mixture once I get the kit. Now I'll make sure I thoroughly flush and refill the system with water before testing.
     
  3. TrunkMonkey

    TrunkMonkey Well-Known Member

    BTW, the "color" is normal for Evaporust/Thermocure. The "grey" is the iron removed from the iron oxide, and binds with the sulfur in the solution to create ferric sulfate, and that will eventually turn the Evaporust/Thermocure black, where it will no longer be very effective.

    I think the hydrogen sulfide is detected by the "leak tester solution" and since the Thermocure has sulfur component, it triggers the "leak detector" solution to a false positive for combustion gasses.
     
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  4. accelr8

    accelr8 Well-Known Member

    Well, I ran the test today and determined there's combustion gas in the coolant system. I guess the heads will be coming off. Thanks for everyone's advise!
     
  5. rjay

    rjay Active Member

    This may be of some help, if you were to allow the car to cool down to ambient temp then release the pressure ,re tighten the cap then wait a day or two , should there then be pressure ,this could be caused be a chemical reaction of the Thermocure and the iron oxide in the block,these reactions will release gas and can persist for some time .
     
  6. Buickone

    Buickone Founders Club Member

    Wouldn't the spark plugs (or plug) look different in the cylinder that had the bad gasket?
     
  7. accelr8

    accelr8 Well-Known Member

    I contacted the makers of Thermocure and they said it would not create pressure in the system and there must be something else going on. Also, I did relieve the pressure, tightened the cap, and came back several days later (without starting the car) and there wasn’t any pressure.


    I plan to pull the plugs, just haven’t gotten around to it yet.

    The oil didn’t look bad (not milky), but there was some copper in it. I’m guessing some coolant got into the oil. I’m going to crack the oil drain plug and see if any coolant comes out.
     
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  8. Mark Demko

    Mark Demko Well-Known Member

    Copper=bearings
     
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  9. accelr8

    accelr8 Well-Known Member

    Yep! Even if I get lucky and this is just a head gasket issue, I think I still need to inspect the bearings. Unfortunately, I think the car will be sitting in the garage for awhile, until I'm able to dedicate the time (and find the room) to dig into this. Good thing this is just a hobby. :)
     
    TrunkMonkey likes this.
  10. accelr8

    accelr8 Well-Known Member

    Update: A friend of mine is letting me use his heated garage, so we pulled the engine and took it apart. The good news is it's just a head gasket issue ... the block and heads checked out fine. The bad news is the bearings are pretty messed up. Hopefully, by springtime the engine will be back together and I'll be cruisin' again.
     
    Mark Demko likes this.
  11. Max Damage

    Max Damage I'm working on it!

    Why would the bearings be toast if it was "just a head gasket". Which bearings are you referring to?
     
  12. accelr8

    accelr8 Well-Known Member

    Sorry, I guess I didn't explain that well. I think it was a blessing in disguise that the coolant system was pressurized. That made me check the oil to see if there was coolant in it. There wasn't, and the oil looked fine. However, while I was under the car I noticed the oil filter housing had a small drip. When I pulled it off to clean it up and reinstall it I noticed some copper sparkles. Not a lot, but some. So I knew something was going on with the bearings. That's why I pulled the engine apart. (Strange, but I never seen anything of concern with the prior oil changes.) All the main and rod bearings had scrapes in them. The front and #4 mains were the worst with a lot of copper showing. The cam bearings were fine.

    When I bought the car 1-1/2 yrs ago the timing chain was broke and I didn't know much about the engine. I replaced the timing chain, put 10w40 in, and went on my merry way for the next year. Well, two problems with that. In hindsight, I think the prior owner ran 20w50, so the 10w40 dropped the oil pressure. Also, my oil pressure gauge is mounted just above the center counsel (where an 8-track player would go) so I never was able to look at it when at WOT (because I'm watching the road). But this past fall I had a friend watch it and I was only getting 40 psi at WOT. My adjustable oil pump was adjusted too far out (and I was using lighter oil). I'm guessing the lack of oil pressure hurt the bearings. (My rookie mistake!) Also, the scrapes indicate there was debris in the engine at some point.
     
    Mark Demko likes this.
  13. Schurkey

    Schurkey Silver Level contributor

    1. FAR more likely for damaged/scored bearings to be caused by debris in the oiling system than mere lack of oil pressure.

    2. If you think you have a gasket problem, you've probably also got issues with the castings the gasket seals against--warped, rough, lack of clamp load from the fasteners not being torqued appropriately. Be sure those castings are FLAT and SMOOTH, and reassemble with the threads in the castings and fasteners in good condition, properly lubed according to the service manual or standard practices, and tightened properly.
     
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  14. Stevem

    Stevem Well-Known Member

    Consider yourself lucky that the head gasket issue took place before any bearings spun.

    With all the crap and grit now in the motor and with it on a stand I could take the time needed to confirm that every lifter spins when the motor is spun over several times.

    How do your cylinder bores look?

    Are there light vertical scratches in them ?

    How do the piston skirts look?

    How does the top ring look, are there scratches where grit has cut thru the Gray Moly face?

    Once everything is looked at I would flush out the oil galleys to be sure there is no more crap lurking in them.
     
  15. Schurkey

    Schurkey Silver Level contributor

    Oh, yeah. I forgot to mention in my previous post:

    3. This is the perfect time to have the block cut for adequate quench distance and uniform compression. GM block decking was never all that precise; common for one side of the block to be taller than the other side; or variations front/rear. You now have an opportunity to correct that poor machining by getting the block square-decked at minimum, or square-decked plus some extra depending on what pistons you're going to put back in.

    4. Buying pistons from Tri-Shield can get you proper quench without carving excess material from the block. The block still needs to be cut flat, smooth, level, and even.
     
    Last edited: Dec 8, 2022
    Mark Demko likes this.
  16. Mark Demko

    Mark Demko Well-Known Member

    Go for zero deck.
     
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  17. accelr8

    accelr8 Well-Known Member

    Thanks for all the input!

    The block, heads, and rotating assembly are at the builder now.

    The builder was concerned about the head to block mating surfaces. He plans to install the four pistons in the corners, check deck height, and then mill the deck to ensure the surface is flat and all pistons have the same deck height. He plans to mill the heads as well. The problem is I checked the deck height on #1 and came up with 0.005", so I don't think we have a lot to work with.

    My recollection is all cylinder bores and piston skirts look good with the exception of #1. #1 cylinder bore and skirt had a small vertical scratch. He's going to try to hone the bore and see what happens. He said he may be able to lightly sand the skirt to remove any high spots. Hopefully, that resolves those issues so I'm not into boring the block and new pistons.

    I'm not sure about the condition of the rings, but I plan to replace them anyways.
     
  18. 12lives

    12lives Control the controllable, let the rest go

    That was quick! Did you figure out the displacement?
     
  19. accelr8

    accelr8 Well-Known Member

    Yep
    • 468 cu. in.
    • 10.6:1 comp.
    • Eagle H-beam rods
    • Wiseco PT pistons with valve reliefs
    • Ported 71 cc heads with Stage 1 valves.
     
    sean Buick 76 likes this.
  20. Schurkey

    Schurkey Silver Level contributor

    That only works if the rods are the same length, the pistons have the same compression height, and the crank has perfectly-indexed stroke at exactly the correct amount. It does give you a "reasonable" guesstimate of the amount of material to be removed, though.

    Better to align-hone the block, then center the block in the milling machine based on the main saddles, instead of assuming the crank, rods, and pistons are "correct".
     
    Last edited: Dec 8, 2022
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