Full Rebuild 08 3.7L H3 Adventure Package

[H3Harley]

Hey fellow H3 lovers! Currently working on a total rebuild of our 08 3.7L Hummer H3. Reaching out to all those left fighting to keep the H3 around for the long haul! Here’s a bit of our journey, I appreciate anyone willing to read and send specific experienced suggestions.


I’ve had a 08 H3 with Adventure package since July 2014. I got transferred for work to Colorado in 2017 and our original 3.7L engine blew 3 months later. The best explanation we got from the GM dealership there was “ a bolt wiggled lose and caused unrepairable damage to cylinder one”. We were stuck and not wanting to give up on our Hummer so we did a lot of research and found a company called Thunderbolt out of Houston TX who sold us a fully remanufactured 3.7L 5 cylinder engine for the 08 H3. We had the dealership in Colorado install it and then we moved back to Texas. 2,000 miles later the transmission blew. We decided to go with a full transmission rebuild in early 2019. Come August we notice signs of fluids mixing in the reservoir (4K miles since new engine 1,200 miles since new transmission). My Husband is a mechanic and is conveniently working at a Chevrolet dealership. He was able to start digging around and found that the head gasket had damage but there was no signs of overheating. We sent the engine back and they discovered it was due to manufacture defect.


We have since received a new engine from Thunderbolt. My husband will be doing all the work and rebuild this time around because we want to make sure she is finally handled right so we can keep her around for the long haul!


We have cleaned up all parts, lines, reservoir, replaced air filters, spark plugs etc. However we are going to be getting some new parts and we are looking for specific part/brand suggestions or modifications made from OEM. Specifically on the radiator, condenser, water pump (felt gasket replacement 2x both times cause small leaks)


This is where I would love H3 specific suggestions on upgrades worth making! Thank y’all!

 

[3Hummers]

I never had to replace the radiator but I know many have upgraded the radiator with great results. I am sure some of those will chime in shortly with what/where they bought. Great to hear that you are restoring your H3.

 

[H3Harley]

Appreciate the support!

 

[JPaul]

Oem parts where you can, aftermarket is rarely as good. Yes it's more expensive but they last longer.

Upgraded aluminum radiators seem to be hit or miss, some have great results, others end up with perpetual pinholes in them.

As for the gasket failing repeatedly, where you using Felpro or something else? Never seen a gasket fail that repeatedly without either it being garbage parts or some other damage on the sealing surfaces that isn't getting addressed. Doesn't take much to get a groove, sratch, or enough buildup to keep a felt/paper gasket from sealing correctly. May also want to use some paper gasket sealant (NOT RTV) next time as well. Permatex makes a bottle of it most auto parts stores carry. It brushes on and is pretty tacky and seals very nicely.

Sent from my SM-N975U using Tapatalk

 

[08H3]

Stick with the GM radiator in my opinion. My first one went around 175K, so I'm not complaining.

 

[Jeepwalker]

While the engine is out, would be a good time to replace the steering intermediate shaft and possibly other steering parts -- make a big difference in how 'tight' it drives. As for the engine, IDK that I'd ever buy a rebuilt engine from a rebuilder that wasn't GM/Ford/Mopar. Ya just hear too many bad stories. Rather either rebuild or buy a used one and rebuild, just like your husband is doing now.

I'm with the other guys, stick with GM whenever possible. I didn't get the number of miles on your vehicle: if it's possible I'd suggest he stick a camera scope down into the header and try to get a 'visual' on the condition of the catylitic converter's condition. Like if it appears to be plugging up or not. They're not cheap, but if ya knew it was becoming a problem, the time to replace is when the engine is out. Also check the intake manifold for carbon build-up and that kind of thing. The sunroof gaskets leak on these rigs by now ..I'd replace with a new one while they're still available, if yours has one. Save yerself from going through all the wet carpet problems every third-poster on this forum goes through (be sure to clean the front drains out at the firewall if he hasn't lately). If it leaks and the carpets get soaked, the foam under the carpet is like a 'super-absorber' and ya got to remove a lot of the interior plastic, seats, console, etc to get it out ..and then it can take a week in the sun for it to dry out. So being proactive on the sunroof waterproofing is a good idea.

Check the driveshaft bushing play at the rear of the transfer case if yours has a lot of miles. And also the back/fourth wear. GM has a kent/moore tool to easily replace that bushing and I'm sure his dealership has it. When left too long vibrations feed back into the xfer case and just cause problems with the bearings. Just keep all the fluids replaced and hopefully with a refreshed engine she'll be good for many more miles.

Put it up on the hoist, remove all of the suspension links and rotate the joint studs 'completely' while pressing on the boots to work some grease around. It's easy to do and will really extend the life of all the ball joints and steering joints. Easier and cheaper than replacing them. They used polished stud ends in nylon-bushed cups ..so the grease doesn't get worked around as much. So, proactively working grease back in there will extend the life of what you have. This is just for people who are in it for the "long haul".

I personally don't advocate lubing up door bushings. I'm not exactly sure what GM uses, but many mfgrs have switched over to a bushing that has a compressed graphite and brass-impregnated bushing. I've found that oiling them actually shortens the life, not extends them. But there are a lot of pro-active things a person can do to extend the life of a vehicle.

Good luck !

 

[Jeepwalker]

Oh, another thing too. If you're in it for the 'long haul', you might have your hubby put it up on the hoist and check the inside front CVs for up/down excess play (at the front diff). Especially on the DR side. (not uncommon). Usually new bearings and maybe a CV does the trick. Oh and of course the bushings on the front diff and steering rack. Even if they've been replaced before. They're not long-lived.