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Thread: T3 Cometic Head Gasket Coolant Leak

  1. #1
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    T3 Cometic Head Gasket Coolant Leak

    So, I've been dealing with a misfire in my R/T for the last few months. The car only misfires for a few seconds if it has been sitting for more than an hour or so. Well, after troubleshooting a few ignition things, I decided to pressurize the coolant system and pull the plugs. After an hour or two, sure enough, I had a little puddle of coolant on cylinders #2 and #3. A few years ago I replaced the head gasket with a cometic gasket sprayed with copper on both sides. I removed the head due to the typical oil leak at the corner of the head. Both the head and block had a good surface finish (If I remember correctly, I used one of those plastic finger finishing tools).

    Anyway, I was expecting a bunch of cracks in my cylinder head since the car has had small coolant leaks for years and I figured a little air in the system caused a hot spot in the head and a few cracks. So far, I've been unable to find any cracks. The head is soaking in some identification dye right now, so I'll let you guys know if I find any cracks. The car was never overheated.

    So far, no obvious cracks in the deck of the head, no external plug leaks (I replaced the core plugs in the head with aluminum years ago). I'm going to check the head for flatness, check the block for cracks, and if I can't find anything, I'll assume the gasket was weeping coolant.

    If everything else checks out, is a modified T2 gasket still the way to go? If the head and block are flat, I'm not sure I want to re-use the cometic gasket. Anyway, let me know what you guys think. For the sake of completeness, the car was assembled with torque to yield bolts (I'll check the threads for yielding while I'm in the garage).

    Pictures of the gasket, starting with an overall, then cylinder by cylinder, starting wtih #1:







    So, after a closer look, cylinders 1, 2, and 3 had coolant in them after a long duration pressure test. Notice a trend in the close-up pictures? I'm down to bare steel on cylinders 1, 2, and 3.
    Last edited by jckrieger; 10-22-2015 at 09:50 PM.

  2. #2
    turbo addict iTurbo's Avatar
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    Re: T3 Cometic Head Gasket Coolant Leak

    I've installed a TIII Cometic head gasket once before and am just about to do it again. Although in my case, I'm using ARP head studs. So far no problems at all...

    After you find out if there are any cracks, flatness etc....I would switch to ARP head studs and install a new gasket or just reuse the old one after cleaning and some fresh copper spray. Just a guess here, but I'm thinking the torque-to-yield bolts are allowing the gasket to weep.

  3. #3
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    Re: T3 Cometic Head Gasket Coolant Leak

    I don't know if more clamp load would have prevented this. All I know is it was really annoying pulling the car apart. The head is flat and there are zero cracks (confirmed with dye penetrant and developer). The only place there could be a crack in the head and get into the cylinder is if it's in the exhaust port (I don't have the manifold off yet). I think this is unlikely, and the gasket wear is unlikely to be a coincidence.

    If anyone reading this has re-used an MLS gasket, can you tell me if the missing coating between the cylinders is normal? I'm pretty sure the missing coating around the coolant passages are likely the root cause of my slow coolant leak into the cylinder. I'd feel more comfortable re-using the gasket if all of the coating was there, or if none of it was there. Any step in the thickness isn't going to be a good thing.

  4. #4
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    Re: T3 Cometic Head Gasket Coolant Leak

    You can't reuse that gasket as is. It's scuffed because the surfaces (block/head) are too rough. The seal coating is basically scrubbed off. By themselves, the steel layers are too hard to seal the head/block. Maybe if a guy could get all of the black sealer off and use
    http://hylomar.com/hylomar-product-r...#universalblue
    ... that might seal up.

  5. #5
    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: T3 Cometic Head Gasket Coolant Leak

    I've seen a few cases of what appears to be some core shift allowing the seam in the block to leak coolant into cylinders even though they look pretty good. Are you certain that it couldn't be coming from the middle of the bore? I'm guessing when you're pressurizing that you've got two pistons at TDC and two at BDC? I'm guessing that it would eliminate that low probability failure from the list of potential problems.

  6. #6
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    Re: T3 Cometic Head Gasket Coolant Leak

    Quote Originally Posted by cordes View Post
    I've seen a few cases of what appears to be some core shift allowing the seam in the block to leak coolant into cylinders even though they look pretty good. Are you certain that it couldn't be coming from the middle of the bore? I'm guessing when you're pressurizing that you've got two pistons at TDC and two at BDC? I'm guessing that it would eliminate that low probability failure from the list of potential problems.
    The middle two cylinders were damn near TDC when coolant was pooling on them. I didn't realize there was coolant in #1 until I pulled the head. Now I see why car companies had some growing pains with MLS gaskets.

  7. #7
    turbo addict iTurbo's Avatar
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    Re: T3 Cometic Head Gasket Coolant Leak

    I hear you on the frustration of having to pull it all apart.

    The ARP studs would be more even clamp load, not just more.

    I would think that the copper gasket spray or the hylomar that puppet suggested could make up for the gasket deficiency. I could be wrong and the thought of having to pull it all apart if it doesn't work out sucks. Is it a daily driver or a tinker toy? If you only plan to do it once (of course), a new gasket may be in order.

  8. #8
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    Re: T3 Cometic Head Gasket Coolant Leak

    Both the block and head have to be prepped for an MLS gasket otherwise it will fail over and over again. Just use a standard one.

  9. #9

    Re: T3 Cometic Head Gasket Coolant Leak

    Quote Originally Posted by Shadowv4l View Post
    Both the block and head have to be prepped for an MLS gasket otherwise it will fail over and over again. Just use a standard one.
    This is right^ With the block deck perfectly clean, lay a straight edge across the web between cylinders, front-to-back; then using a feeler gauge; see if or how much the surface of the web area has receeded. If it is more than a couple thousands it will leak from the deck or head crossdrill holes.
    The MLS gasket in the photos is junk now. in order to be successful with an MLS the surface finish needs to look like this.........Almost a mirror finish, then they work very well. If I were you, I would go back to using the Mopar Performance style, composite gasket sprayed with copper coat.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	StramerJE custom piston and Callies rod 013.jpg 
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    Last edited by Warren Stramer; 10-23-2015 at 09:25 AM.
    Worlds fastest 8 Valve 6.3sec., 119.70 1/8, Best MPH 145.5, Best 1/4 ET 9.82 sec.,143mph. 8 valve NO NITROUS!!

  10. #10
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    Re: T3 Cometic Head Gasket Coolant Leak

    The issue with using a composite gasket is, well, they don't exist! I can attempt to cut holes in a T2 gasket and make it work, or I can try to do something MLS (only thing commercially available). In this case, the leak was between the head and the gasket, and the surface finish on the head is really good (I'll take a picture once I get the developer cleaned off). I'm not sure why the coating failed, but maybe I'll find out once I check the block.

    I agree the surfaces need to have an excellent finish. In cases where the finish isn't perfect, *some engine manufacturers* use this:

    http://www.amazon.com/gp/product/B00...ilpage_o00_s00

    My plan is to remove the coating from the top side of the gasket (where the coating is damaged), then carefully prep the head and block surfaces (I'll check the block for flatness first). I'll then use the sealant on both sides of the gasket. Hopefully with an improved sealant and an improved surface finish the repair will last a long time. Even at 110K, the cylinders look perfect. This car has a lot of life left!

    I think I can get the head and block cleaned up to a nice surface finish. I'll 3d print some plugs for the cylinders and oil passages to help eliminate the possibility of any grit getting into the oil system. I don't think this will be an impossible task.

    And Warren, as usual, that block is a work of art!

  11. #11
    turbo addict iTurbo's Avatar
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    Re: T3 Cometic Head Gasket Coolant Leak

    I too wish that the stock TIII head gasket were still available. Unfortunately no aftermarket and there never was a Mopar Performance version.

    If it were available, that is what I'd be using. But Cometic seems to be the only way.

  12. #12
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    Re: T3 Cometic Head Gasket Coolant Leak

    Well... bust out your sanders and polishers! Lol

  13. #13
    turbo addict iTurbo's Avatar
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    Re: T3 Cometic Head Gasket Coolant Leak

    Warren, where are you going for machine shop work? Or are you doing this all yourself? I've recently stopped going to my local machine shop. They do great work but, since they are the only one in town, the wait times are extensive. Now I go to RPM Machine in Sturgis and have been happy so far.

    Looking at the block pic you posted, wow! I thought it looked weird and then I realized it was reflections.

  14. #14
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    Re: T3 Cometic Head Gasket Coolant Leak

    FWIW, I'm using this gasket on my Spirit R/T with no issues.

    http://www.amazon.com/gp/product/B00...ilpage_o01_s00

  15. #15
    Supporting Member Turbo Mopar Contributor 2.216VTurbo's Avatar
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    Re: T3 Cometic Head Gasket Coolant Leak

    [QUOTE=jckrieger;1094195]The issue with using a composite gasket is, well, they don't exist! I can attempt to cut holes in a T2 gasket and make it work, or I can try to do something MLS (only thing commercially available). In this case, the leak was between the head and the gasket, and the surface finish on the head is really good (I'll take a picture once I get the developer cleaned off). I'm not sure why the coating failed, but maybe I'll find out once I check the block.

    I agree the surfaces need to have an excellent finish. In cases where the finish isn't perfect, *some engine manufacturers* use this:

    http://www.amazon.com/gp/product/B00...ilpage_o00_s00

    My plan is to remove the coating from the top side of the gasket (where the coating is damaged), then carefully prep the head and block surfaces (I'll check the block for flatness first). I'll then use the sealant on both sides of the gasket. Hopefully with an improved sealant and an improved surface finish the repair will last a long time. Even at 110K, the cylinders look perfect. This car has a lot of life left!

    I think I can get the head and block cleaned up to a nice surface finish. I'll 3d print some plugs for the cylinders and oil passages to help eliminate the possibility of any grit getting into the oil system. I don't think this will be an impossible task.]

    IMO, if you're really gonna prep an MLS gasket Clark, ya gotta grind the rivets apart and prep both sides of EACH LAYER individually. I sorta skim read this thread and it was a late night last night so excuse please if someone else already mentioned it

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  16. #16

    Re: T3 Cometic Head Gasket Coolant Leak

    What holes would have to be made in a T2 gasket to make them usable with a 16V?, I'm not that well versed in the Lotus head.
    Worlds fastest 8 Valve 6.3sec., 119.70 1/8, Best MPH 145.5, Best 1/4 ET 9.82 sec.,143mph. 8 valve NO NITROUS!!

  17. #17
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    Re: T3 Cometic Head Gasket Coolant Leak

    IMO, if you're really gonna prep an MLS gasket Clark, ya gotta grind the rivets apart and prep both sides of EACH LAYER individually. I sorta skim read this thread and it was a late night last night so excuse please if someone else already mentioned it
    Woah ... why would you have to do all of that?

    http://www.rockauto.com/catalog/more...nid=534&jpid=2 Warren, that's a link to a t2 gasket to compare with the other pic in the OP

  18. #18

    Re: T3 Cometic Head Gasket Coolant Leak

    OK, now could someone post a pic, or a link to a pic of a TIII head, gasket /combustion chamber side.
    I had to find a way to punch clean holes in head gaskets in order to accommodate an extra row of head bolts. I purchased one of these tools http://www.harborfreight.com/9-piece...set-95547.html. This will punch clean holes even trough my Commetic steel shim head gaskets, one thickness at a time. The other tool I use is a stepped Uni-Bit, they also make clean holes in sheet stock.

    Maybe I should start making Composite TIII head gaskets out of T2's, looks like childs play.
    Last edited by Warren Stramer; 10-25-2015 at 10:05 PM.
    Worlds fastest 8 Valve 6.3sec., 119.70 1/8, Best MPH 145.5, Best 1/4 ET 9.82 sec.,143mph. 8 valve NO NITROUS!!

  19. #19

    Re: T3 Cometic Head Gasket Coolant Leak

    Quote Originally Posted by iTurbo View Post
    Warren, where are you going for machine shop work? Or are you doing this all yourself? I've recently stopped going to my local machine shop. They do great work but, since they are the only one in town, the wait times are extensive. Now I go to RPM Machine in Sturgis and have been happy so far.

    Looking at the block pic you posted, wow! I thought it looked weird and then I realized it was reflections.
    I do all my own head work, the boring and decking I farm out to a friend in Minot, He's built race engines for 40 years, everything from Super Stock to Top Fuel nitro Hemis.
    Worlds fastest 8 Valve 6.3sec., 119.70 1/8, Best MPH 145.5, Best 1/4 ET 9.82 sec.,143mph. 8 valve NO NITROUS!!

  20. #20
    Supporting Member Turbo Mopar Contributor DOHCRT's Avatar
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    Re: T3 Cometic Head Gasket Coolant Leak

    Quote Originally Posted by Warren Stramer View Post
    What holes would have to be made in a T2 gasket to make them usable with a 16V?, I'm not that well versed in the Lotus head.
    A trick I learned from Neil Emiro and one that I use on all of my TIII's is to use a stock (FelPro) TII gasket and drill a few holes in the head to line up the cooling passages with the gasket. Now I can us any stock TII gasket and not have to worry about modification if something happens away from home base. I have been running this mod since around 2000 and Neil has used it prior to that. 21-25 psi has not been a problem and once the Holset goes on this winter we will look to up the ante.


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