# 8 engine problem

H1 (Hummer) & HMMWV Specific Information

Re: # 8 engine problem

Postby Greenmeanie » Fri Jul 23, 2010 7:11 pm

So far i have been lucky i guess. My 97 HMC4 still has original motor H296 and i am at 111.000 miles. I have had a few white smoke scares when it starts getting cold but thats it. I also kick the snot out of the truck as well and i have never seen the temps go above 220F. The hottest it will get is on the highway doing 80mph and it cycles to 215 and backs down to 200 or so as the fan clutch opens and closes. The rest of the time it stays at 200F +- 10%. If I blow the motor i will probably go with the optimizer replacement. I am not thrilled by the duramaxes low end and its a lot of money.
1997 HMC4 G10 green, 110k no cracks yet, original H296 engine UPDATED MILEAGE 120,168
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Re: # 8 engine problem

Postby redwood » Sat Jul 24, 2010 9:47 pm

Is the odds off the problem lessoned by being in the north where its not so hot all year or does this have to due with just engine temp.
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Re: # 8 engine problem

Postby mhr900ss » Sun Jul 25, 2010 12:45 am

redwood:
The #8 problem is due to a casting design problem - it's a ticking time bomb. My truck was babied and carefully maintained and driven. All you can do is to keep your coolant system in top condition and hope your block does not fail.
Rick 98 HMCS TD
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Re: # 8 engine problem

Postby JustinOK » Sun Jul 25, 2010 2:41 am

The coolant temperature gauge is kind of a bad way to "gauge" how cool the engine is. The sensor is nowhere near the area of the block that is prone to cracking. So while the sensor is showing maybe one thing, the area nearest the #8 could be something else. Just keep that in mind.

I babied my truck as well, never saw temps above 205 F while driving around. I always drove 55 mph and that would almost always give me 191 F exactly, per my ScanGauge II.
1998 TD 4 Door Hard Top (HMC4) w/ 91K miles
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Re: # 8 engine problem

Postby rijowysock » Sat Jan 19, 2013 1:47 am

i notice the one reply said 97-99 is affected years, did they correct the casting issue for 00 vehicles?

hard to find exact info on this.
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Re: # 8 engine problem

Postby JustinOK » Sat Jan 19, 2013 9:50 pm

rijowysock wrote:i notice the one reply said 97-99 is affected years, did they correct the casting issue for 00 vehicles?

hard to find exact info on this.


Some 2000's had the updated block from the factory, some did not. A visual inspection really is the best solution to determine if you have an updated block or not. It could be possible the engine has been swapped out since that truck would be 13 years old this year. The VIN is not the end-all be-all. Unless of course it has an F as the 4th character, but that only applies to the 2001 and newer trucks.

http://www.lynchhummer.com/Changes/h1.c ... 00/00.html

Enhanced engine block- Turbo Diesel Engines with block castings before May 1999 are susceptible to #8 cylinder cracks. Most frequently the first symptom of a cylinder crack is coolant being forced out of the cooling system causing the "check coolant" light to illuminate. Many engines have been replaced with blocks of the same design. Even though the enhanced blocks were first produced in May 1999 it took some time before they made their way through the system and into Hummers as either original equipment or for replacement. Even Hummers produced in 2000 are likely to have the pre-May 1999 block casting. There is a casting number on the right rear of the block under the cylinder head which should be E_99 (May 1999) or later. Unfortunately the codes changed through the years so identifying the enhanced blocks is even more difficult. Later blocks also use metric bolts to attach the bell housing but it is unclear whether this clearly identifies an enhanced block. Although enhanced blocks were installed in Hummers produced before the engine manufacturer change to General Engine Products (GEP), the easiest way to make sure a Hummer left the factory with an enhanced block is to check the 4th digit of the VIN on 2001 and later 6.5L turbo diesels. If the 4th digit is an "F" the engine was produced by GEP and is sure to have the enhanced block from the factory.
1998 TD 4 Door Hard Top (HMC4) w/ 91K miles
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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 telazra » Sat Jun 27, 2015 3:46 pm

Hi, I am look at purchasing a 1998 H1 with the original engine and concerned about the #8cylinder issue.

Does anyone know if replacing the engine was originally a recall by AMG/GM or if it was replaced only if the engine cracked? Also, am wondering if AMG/GM will replace the engine now after 17 years.

TIA
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Re: # 8 engine problem

Postby JustinOK » Wed Jul 01, 2015 11:35 am

telazra wrote:Hi, I am look at purchasing a 1998 H1 with the original engine and concerned about the #8cylinder issue.

Does anyone know if replacing the engine was originally a recall by AMG/GM or if it was replaced only if the engine cracked? Also, am wondering if AMG/GM will replace the engine now after 17 years.

TIA


There was no recall for engine replacements; if the failure happened under original warranty then it would have been covered. Your engine will not be replaced by AM General or GM at this point. The only way it could be *possibly* replaced for a low cost, would be to purchase an after-market third-party warranty, but you'll have to do that research.
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 telazra » Sun Jul 19, 2015 3:36 pm

Hi, thanks for the reply. Anyone in Austin/San Antinio that can refer a good shop for H1 service and maintenance?
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Re: # 8 engine problem

Postby Ian Ward » Thu Dec 03, 2015 8:53 am

I service all the hummers /hmmwv in the aistin area that i know of. I can be of assistance. I have been working on hummers for years. I have been working for myself now for about 3-4 months. I have been so busy working on hummers i have not had the time to look for other customers. I have have a customer truck with a cracked block right now. Its probably the worst smoking and loudest rod knocking i have herd in a while. I have a heavy equipment and truck background. I list my contact info below. Yall can call or email me- thats why i use my real name and put my real phone number. I dont do the Forum thing very often so for a fast response call or email.
Iandanielward@yahoo.com
Thanx,
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Re: # 8 engine problem

Postby Ian Ward » Thu Dec 03, 2015 8:59 am

I thought my contact info was in my signature.

Ian Ward
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Re: # 8 engine problem

Postby bobby1983 » Thu Apr 07, 2016 7:07 pm

are signs of a #8 cylinder issue similar to a blown head gasket?
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Re: # 8 engine problem

Postby JustinOK » Sat Jul 23, 2016 10:33 pm

bobby1983 wrote:are signs of a #8 cylinder issue similar to a blown head gasket?


Yes. Low compression is a given, sometimes you might get oil in coolant or coolant in oil, coolant (white vapor) out the tail pipe, and loss of coolant are some of the signs.m One easy check you can do is to look pressurization in the coolant reservoir after one minute of run time (indicates possible problem). Just make sure the vehicle is "cold" first, and you open the cap before starting to make sure there is no previous pressure built up.
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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