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The Hummer Knowledge Base

High Mileage - Some tips for the 100,000+ mile HUMMERs:

A few things for your high milege HUMMERs.

The CDR valve. If you have not done so I'd say replace it. You can try and clean it out, but it would be better to replace it. Mine was full of grease [Shocked] . Also make sure the hose connecting to it is free of obstructions, mine had that greasy crap in the hose too. Due to the shape of the hose its a PIA to clean out, but do able.

The carrier bearing. Just replace it. Mine was getting worn out feeling so I decided to swap it. Even though it didn't feel too bad once apart it was clear the bearing was toast. While your at it put new U-joints in, they are cheap and easy to replace so while the drive shaft is out get them done too.

While the drive shaft is out (and it needs to be for this repair)replace the oil filter housing o rings. There are a total of three. One large ring around the filter housing itself, and two smaller ones located on the shaft of the bolt. If your oil filter is covered in oil its probably due to these o rings. Once I got the housing out and got a look at the o rings they were clearly past due for replacement. They were very hard, not plyable, and the shapes had distorted.

Check around for leaks. I had a couple of oil leaks that I felt needed to be addressed. I also had some small fuel leaks.

Replace the injector return lines, four of mine were leaking. This has been an on going problem for me though. I reccomend only using the lines that covered with a braided wrap, if you can find it.

Now is also a good time to check all the hoses over. I blew out the upper radiator hose last year and it was quite rotted.

Now is also a good time to check your motor mounts, they could be getting worn out by now.

Also check the harmonic balancer along with the fan clutch.


Check your hoses and belts not only due to mileage, but also age. I bought my 93 Hummer in 2002, it had only 34K on it at the time but the belts and hoses were all dry rotted. I had a heater hose burst and after inspecting the other hoses many of them were showing signs of cracking, so I replaced all of them.


The front crank pulley and Harmonic balancer are wear items, 100K is the time to replace IMHO, possibly earlier. For the Turbo diesels, you might also want to replace the vacuum solenoid for boost control.


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