# 8 engine problem

H1 (Hummer) & HMMWV Specific Information

# 8 engine problem

Postby redwood » Sun Jul 18, 2010 5:15 pm

What are the signs of the # 8 problem when it happens. I have a 98 H1. Do all 6.5 turbos have this problem or has someone made it to 100,000 w/o problem. Can you prevent the problem.
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Re: # 8 engine problem

Postby mhr900ss » Sun Jul 18, 2010 6:38 pm

Hi Redwood:

There are lots of warning signs and if yours is an original motor then you are prone to the problem. There is a lot of info on the following sites to read about this issue:
http://flashoffroad.com/
http://www.humvee.net/

The main thing to do is maintain the truck as best you can so that the coolant and oil systems are in great condition. Watch the temperature guage carefully so you become very familiar with what "normal" behaviour is. Typical indicators of a cracked block are white smoke in the exhaust (this can be just a little at start-up or lots), fast pressure build-up in the coolant reservoir, odd temperature fluctuations. It can happen with relatively low miles or lots. There is a basic engine design flaw and that's that.

One test for a mild crack is to wait until the truck is cold then lift the hood and release the coolant tank pressure then reseat the cap. Start the motor and run for about a minute then shut down and reopen the cap. There should not be any pressure in such a short time. If there is, it is likely that exhaust gases are escaping into the coolant system via a crack.

Despite all of this my motor just decided to blow one day. I had no white smoke, no pressure build-up, just one small temp swing one day - went up to 240 for a few seconds and bounced back down to 210ish. Next day my motor suddenly gushed a huge cloud of white smoke. I was sure it was a blown head gasket due to the sudden nature of the event but no, #8.

I bought my 98 4 years ago after lots of reading so I have no one to blame but myself. Frankly, I would never recommend buying a 97-99 H without a new motor already installed. I babied my truck and can confidently state that my engine failure was not due to lack of care and attention. It is apparent from the number of Hummers of this age that suffer #8 that it is almost inevitable that this will happen.

If the truck is relatively new to you and you have not done much yet and there does not appear to be anything wrong here's where I would start:
- Get the coolant system flushed and filled with a good diesel motor specific coolant.
- Change the thermostats (there are 2)
- Do the pressure check described above
- You may want to consider getting a new coolant tank pressure cap
- Change out all the flexible coolant hoses - if original - they are getting old and can fail.
- Put $200 bucks away every month into a new motor savings account.

Did you get Breggin's maintenance CD yet?
Rick 98 HMCS TD
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Re: # 8 engine problem

Postby JustinOK » Sun Jul 18, 2010 7:25 pm

Hate hearing stories of those with the #8 problem. I have known a #8 to manifest it self as late as 120,000 - 129,000 miles, this was on a 97.5 year truck. Mine never became a full fledged #8, but around 67K I inspected my engine during a headgasket failure and found it was ready for a #8 when some discoloration in the #8 cylinder wall was discovered. Got a new engine now, yay. :/
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Re: # 8 engine problem

Postby mhr900ss » Sun Jul 18, 2010 11:47 pm

I hear you Justin! I've had fingers crossed for years. Everytime one us lost a motor I hoped it wouldn't be me next.
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Re: # 8 engine problem

Postby redwood » Wed Jul 21, 2010 9:35 pm

Thanks for the input guys. Has anyone had luck with this bypass system thats sold. It basically has three hoses and bypasses coolant from two water jacket plugs to the heater lines.
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Re: # 8 engine problem

Postby dailydriver » Wed Jul 21, 2010 10:23 pm

redwood wrote:Thanks for the input guys. Has anyone had luck with this bypass system thats sold. It basically has three hoses and bypasses coolant from two water jacket plugs to the heater lines.


It makes the problem worse and won't fix anything.
Sure the engines have a flaw. I wouldn't pass up a 97.5 or 98 with the original motor if it's your dream truck.
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Re: # 8 engine problem

Postby JustinOK » Thu Jul 22, 2010 1:47 am

dailydriver wrote:
redwood wrote:Thanks for the input guys. Has anyone had luck with this bypass system thats sold. It basically has three hoses and bypasses coolant from two water jacket plugs to the heater lines.


It makes the problem worse and won't fix anything.
Sure the engines have a flaw. I wouldn't pass up a 97.5 or 98 with the original motor if it's your dream truck.


I had my cooling kit installed for over a year and a half and about 8-9K miles, then I had my headgasket failure and noticed the #8 looked ready to go. Not sure if the cooling kit helped the life of the engine or if it decreased it.

Like dailydriver said, if everything else about the truck is good, then talk the seller down some based on the engine, and use that extra money and start saving up for a new engine. Duramax swaps are expensive but a good swap will make a solid truck, Cummins swaps aren't as expensive and will also give you a very reliable and strong struck, and even a new 6.5 from GEP would work out as well. There are options to getting rid of that boat anchor.
1998 TD 4 Door Hard Top (HMC4) w/ 91K miles
Updated block and loaded with parts from Hummer Parts Guy and Blue Hummer

HummerDan's Hardcore Skid Guards, Fender Guards, & Locking Fuel Doors; Ham (VHF/UHF) & CB radios; Predator RapTorq4 PCM; mechanical wastegate; Cepek Adjustable Shocks; D-Tech PMD.
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Re: # 8 engine problem

Postby ronb » Thu Jul 22, 2010 11:42 am

my engine was blown when I bought my truck 6 years ago. I went with a gep 6.5td block to stay stock...if I had to do it again I'd go na mechanical or cummins. The block and labor was about $12k. I still walk funny after that screwing fro 1000 Oaks hummer. It was a good deal until that happened!

I always wondered how much those cooling kits did...but how could they hurt things? I never took auto shop so be gentle on me!

rb
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Re: # 8 engine problem

Postby hummech » Thu Jul 22, 2010 12:12 pm

i don't recommend the cooling kits myself. i was going to install one on the race truck so i called the factory about them. they told me that the kits do more damage because when they dyno'ed the engine with and with out the kit there was a 10 degree difference between the two BUT, the reason the cooling kit ran cooler is because the way the engine is designed, it has block off plates at the back of the head to force the coolant back to the front of the engine over the top section of the engine. it ran cooler because it was not picking up the heat from the top half of the engines and that is why i do so many head gaskets on engine with the cooling loops.
just my .02 worth,
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Re: # 8 engine problem

Postby ronb » Thu Jul 22, 2010 12:33 pm

hummech wrote:i don't recommend the cooling kits myself. i was going to install one on the race truck so i called the factory about them. they told me that the kits do more damage because when they dyno'ed the engine with and with out the kit there was a 10 degree difference between the two BUT, the reason the cooling kit ran cooler is because the way the engine is designed, it has block off plates at the back of the head to force the coolant back to the front of the engine over the top section of the engine. it ran cooler because it was not picking up the heat from the top half of the engines and that is why i do so many head gaskets on engine with the cooling loops.
just my .02 worth,
hummech


hmmmm. next time I'm there maybe we can remove mine!!
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Re: # 8 engine problem

Postby hummech » Thu Jul 22, 2010 12:39 pm

ron your hummer is safe.... you have to be in town to be able to drive your hummer in order for the bypass to do any damage..LOL. no worries, call me when you get some time.

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Re: # 8 engine problem

Postby ronb » Thu Jul 22, 2010 12:56 pm

hummech wrote:ron your hummer is safe.... you have to be in town to be able to drive your hummer in order for the bypass to do any damage..LOL. no worries, call me when you get some time.

hummech


ouch...you kick me while I'm down! Just for that I'm gonna tell everyone you did that 8.1 conversion!!

I seem to be home just long enough to just scratch the surface of my truck's to-do-list then I leave again. I am headed to Dallas in two days to sweat my balls off! Maybe I will see ya in Dec...or if I'm lucky they'll fire me so I can be home by Halloween. Not too happy about all the travel I've had to do the past 2 years but in this day and age any work is good :cry:
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Re: # 8 engine problem

Postby hummech » Thu Jul 22, 2010 2:12 pm

don't sweat your balls off in Dallas, i like busting your balls about how often you are gone. it is great that you are in demand with the kind of work that you do. keep busy and i will see you when you get back.
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Re: # 8 engine problem

Postby JustinOK » Fri Jul 23, 2010 7:18 am

hummech wrote:i don't recommend the cooling kits myself. i was going to install one on the race truck so i called the factory about them. they told me that the kits do more damage because when they dyno'ed the engine with and with out the kit there was a 10 degree difference between the two BUT, the reason the cooling kit ran cooler is because the way the engine is designed, it has block off plates at the back of the head to force the coolant back to the front of the engine over the top section of the engine. it ran cooler because it was not picking up the heat from the top half of the engines and that is why i do so many head gaskets on engine with the cooling loops.
just my .02 worth,
hummech


Damn... kinda wish I knew this before installing my cooling kit. Oh well! It's not on my "new" engine!
1998 TD 4 Door Hard Top (HMC4) w/ 91K miles
Updated block and loaded with parts from Hummer Parts Guy and Blue Hummer

HummerDan's Hardcore Skid Guards, Fender Guards, & Locking Fuel Doors; Ham (VHF/UHF) & CB radios; Predator RapTorq4 PCM; mechanical wastegate; Cepek Adjustable Shocks; D-Tech PMD.
Stanadyne Performance Formula every fill-up and ScanGauge II full time.
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Re: # 8 engine problem

Postby ronb » Fri Jul 23, 2010 12:02 pm

JustinOK wrote:
Damn... kinda wish I knew this before installing my cooling kit. Oh well! It's not on my "new" engine!


it's on mine! And I will try to hold onto my balls so Mike can keep busting them!
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