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GM 12378255 or 10-108 both on package. Have to crush them before adding is what I was told and easiest way is in a zip lock sandwich bag. I am thinking it was 1 tab per gallon and they come on a card of 5 as a single part. the local GM dealer had them on the shelf but forget what I paid for them though sure it was pretty cheap like 10 bucks. I used them on my Pontiac v6 the somehow looked like it got oil in the coolant and was told needed a new intake manifold as it is composite or some such crap along with all new hoses coolant flush with detergents then neutralizer and and until the bill would have come close to 1k. Had them dump coolant and rinse with hot tap water running the engine between doing it a couple of times. I added the tabs when I got the car home drove for 15 minutes and has been 2 years just fine. Same hoses manifold water pump gaskets etc. Dealer thought it was a hail mary deal and would not work but told them if coolant can't get under edge of gasket it can't corrode anything. Smart move now is change coolant every few years as corrosion inhibitors do wear out.
, that's the bottom line. I think the norm is 5 years on antifreeze coolant. you can't believe how many people never service their cooling system. they think "as long as it's green...." fairly sure it's all about the acidic level of the solution. i'm no chemist, but I guess once it drops below the pH 7 level, it starts eating away at the metal parts of your engine and cooling system. . three areas where I probably "over-service" my corvette is the cooling system, (automatic) transmission, and differential. brake fluid is a close second. most of the time, it's because I have nothing better to do. i'm alone, in my garage, spending quality time with baby. its therapeutic -
BTW, and FWIW -- as previously stated, I add three delco cooling tablets to my cooling system after doing a valve job. nowhere on the package directions state to crush the tablets prior to use. I basically popped the radiator cap, and dropped in the tablets. crushing the tablets would not hurt anything though, and I guess it would aid in dissolving the tablets and dispersing the product, but it's not a "have to" thing.
Service manager told me to crush them so they go to work much sooner.
Yes these sealing tabs will plug fine voids & pinhole leaks and should be crushed into a fine powder to facilitate circulation throughout your cooling system.
I want to update you all on my head situation. The advice saved me a bundle and the 91 runs perfect and no coolant loss issues. I did use my old heads with MLS head gaskets (.041" thick and 4.065" bore.) The heads have now been resurfaced twice now, I don't know if the compression has changed much, but runs fine on 93 octane. Thanks again guys, there is some real good info to be had on this forum.
I want to update you all on my head situation. The advice saved me a bundle and the 91 runs perfect and no coolant loss issues. I did use my old heads with MLS head gaskets (.041" thick and 4.065" bore.) The heads have now been resurfaced twice now, I don't know if the compression has changed much, but runs fine on 93 octane. Thanks again guys, there is some real good info to be had on this forum.
I want to update you all on my head situation. The advice saved me a bundle and the 91 runs perfect and no coolant loss issues. I did use my old heads with MLS head gaskets (.041" thick and 4.065" bore.) The heads have now been resurfaced twice now, I don't know if the compression has changed much, but runs fine on 93 octane. Thanks again guys, there is some real good info to be had on this forum.
I want to update you all on my head situation. The advice saved me a bundle and the 91 runs perfect and no coolant loss issues. I did use my old heads with MLS head gaskets (.041" thick and 4.065" bore.) The heads have now been resurfaced twice now, I don't know if the compression has changed much, but runs fine on 93 octane. Thanks again guys, there is some real good info to be had on this forum.
I want to update you all on my head situation. The advice saved me a bundle and the 91 runs perfect and no coolant loss issues. I did use my old heads with MLS head gaskets (.041" thick and 4.065" bore.) The heads have now been resurfaced twice now, I don't know if the compression has changed much, but runs fine on 93 octane. Thanks again guys, there is some real good info to be had on this forum.
Good news to hear.. But what did you use for the fix this time? Sealant tabs? Sealant coated gaskets? Feedback helps us all.
Good news to hear.. But what did you use for the fix this time? Sealant tabs? Sealant coated gaskets? Feedback helps us all.
My fix was MLS head gaskets off of Ebay from CGM Motorsports ($90) and ARP bolts ($75). In the past when I have rebuilt Chevy engines not much attention was paid to head gaskets. I discovered the hard way that the GM head aluminum castings have very little tolerance for generic head gaskets. What I'm trying to say is that the bore size on the gasket needs to be as close to the bore size of the block as possible. No sealants were used, just correct size gaskets.
Hey Polo91 - I know this thread is very old, but I just pulled the passenger side cylinder head on my 91 tonight, and found the same issue I believe you are describing with the coolant passage. Mine had a very slow coolant leak, internal, and I only knew there was a more serious issue when I pulled the spark plug and saw how wet it was. Compression on this cylinder was 20 pounds low, so the leak must have been minimal. I have not had the car long, and had just gotten it dialed in with TunerPro after fixing a bunch of vacuum leaks when I noticed the wet plug, so I am looking forward to fixing this leak and seeing how it runs. I wanted to ask how your repair, and experience with the MLS gaskets was holding up? If you wouldn't mind sharing your feedback, and the part number you ended up going with I would really appreciate it. Thank you
Cylinder #2 Close up Coolant passage cylinder #2 "Good" Coolant passage cylinder #8
D Vettor, your picture of #2 cylinder is exactly the like my #7 cylinder was. The casting is off a bit. The MLS gaskets fixed the problem for over forty thousand miles, but about six months ago I started losing coolant again. I haven't had time to get to it, so I can't be sure it's the same problem. On my #7 in the picture (from 2017) below, the long oval water passage leaked on the right side near the piston bore. If I find the same problem, I'll look for a good original, or go aftermarket. BTW the car still runs great at over 200K.
If you wanted, one can always get the area welded up then re-surfaced, since aluminum is easily welded. Take her to a machine shop to be sure but could be an option.
Thank you for the replies Polo91 and CornHusker. Sounds like your results have been pretty darn good with 40k miles since you fixed it, not bad. Did you have any material added to that head previously - I cannot recall? I was wondering what the feasibility would be of just adding some aluminum there, and it sounds like that would be pretty doable - great! I have the heads in the truck and am taking them by the machine shop tomorrow to see what they say. Be nice if they can shore that area up a bit, clean and check them over. It looks like these 501 SD Head gaskets by FelPro should work well for my condition - Part Details (drivparts.com), but open to any recommendations as well. The best part of having to do this job is having an excuse to pull off all of the smog and AIR components. Going to have the air tubes cut off and holes weled up as well while they are out. Will look so much cleaner and make routing the spark plug wires a bit easier. Take care. Covered up awaiting cleaning so little kids don't drop anything in there...
Dropped the heads off at the machine shop last week, guy said adding some metal to fix that will not be an issue. They'll do that, clean and test, and mill them slightly then I should be good to go. Appreciate all the thoughts and experiences shared.
11-19-2017, 06:33 AM
, that's the bottom line. I think the norm is 5 years on antifreeze coolant. you can't believe how many people never service their cooling system. they think "as long as it's green...." fairly sure it's all about the acidic level of the solution. i'm no chemist, but I guess once it drops below the pH 7 level, it starts eating away at the metal parts of your engine and cooling system. 
. three areas where I probably "over-service" my corvette is the cooling system, (automatic) transmission, and differential. brake fluid is a close second. most of the time, it's because I have nothing better to do. i'm alone, in my garage, spending quality time with baby. its therapeutic - 
