I haven't yet but looking for a response from Blackstone. If coolant is in the water then they both come off whether or not these old eyes can see anything or not. I am realtively certain it is all coming off shortly. LOL. Question for you. Do the 799 heads require premium gas or can I continue to use 87 Octane?
2003 Tahoe coolant system leak or head gasket leak?
- Thread starter tomloans
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Woe the first time I looked I only saw the covers, but I just saw the top of the cylinder head. I am not worthy! I am not worthy!
Had a similar mystery leak, found the info about the Castech heads problem, confirmed the cracks in the head under the rockers, got a package of ACDelco stop-leak tablets mentioned in the related service bulletin and it stopped the problem. I've since put a couple years and some very hard towing miles, high revs high heat, on that motor with no recurrence of the issue.
iamdub
Full Access Member
799 (same as 243) would actually lower the compression a hair, so you'd definitely be safe with 87 octane. The heads do flow better than the 706s, but that only helps top-end power. You may or may not notice any loss from the reduced compression. If you had the heads milled, you'd maintain your stock compression (or improve it a tiny smidge) AND benefit from the higher flow, so it'd be a win-win. But, not really much of a loss if you didn't. For the minimal cost, my preference is to have them professionally cleaned and milled.
iamdub
Full Access Member
lol
I don't know what oil the original owner used, but they definitely had it changed regularly. I bought the Tahoe at 146K and ran either Mobil1 or Pennzoil Platinum, changed every 5K. The teardown in my build thread shows the results of quality synthetic oil changed regularly.
That dirty cover is one I bought to get the updated design. I pulled mine off (the clean one) and saw that I already had the updated one.
Good thing you cleared that up, since I was having trouble seeing any difference, except for clean vs. dirty.
iamdub
Full Access Member
Good to know. Waiting on Blackstone at thr moment to confirm coolant in oil. With a job this big, I want to be absolutely sure. I likely will need your help again. Be in touch soon.
The tablets are definitely tempting for sure. I just can't believe they would stop a crack in the cylinder head. Just to be sure, are you certain you had that crack? Did you stop losing radiator fluid or is it just a slower loss?
iamdub
Full Access Member
That's what we're here for! I'm a bit of a documenter with text and words, so I might have helpful pics and info in my build thread. Reinstallation of heads starts on page 69: https://www.tahoeyukonforum.com/threads/growing-up-doesnt-have-to-suck.93510/page-69
This is great!
iamdub
Full Access Member
Thank you! I hope you find it useful.
Found it I think. What is odd is that there is very little gunk built up on this side. Check out these pics...
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ivin74
05 NBS Nali
Clean the area with carb cleaner to see it the crack shows up.
afpj
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Did you ever put the uv dye in the coolant?
I will.
iamdub
Full Access Member
Sorry, work had me hemmed up the past few days.
That is 100% a clean spot from coolant. Being around the head bolt is the typical Castech failure. There's very little gunk because the leak is very small and only happens when it's up to operating temp and you caught it early. Compared to how bad my brother's was and it's running like a champ, I'd say yours would be just fine with new heads. I keep meaning to dig up the pics of what I found in his engine, but I see a lot of squirrels.
