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6.5 turbo diesel

J

John hanna

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I have a 2002 h1 hummer with a 6.5 turbo diesel in ti . My upper hose keeps pressure in it for days and also the reservoir keeps pressure . When am driving it doesn’t get hot but when am dueling or not moving and the truck runs for few minutes the temp goes high like 220-230 . When I drive it . Temp goes down to 185-200 . Occasionally the water get pushed out of the reservoir and the tem goes back down . Please let me know for any suggestions. Someone told me try some kind of tabs . . And also what would cause that
 
Many things could be going on here. How long have you owned this and how many miles on it? New to you and you are discovering why they sold it? 🤪

Pictures can help answer questions. First a picture of the fan clutch so we can see what kind you have. How old is the fan clutch? I ask as a "root cause" question.

Holding pressure is a good sign. I would suspect the radiator cap is having trouble. Pressure test it. I have had poor quality caps and radiators not release pressure, then blow off suddenly shock cooling the engine, and then suck the hoses flat. I have seen cracked heads tend to leak as the engine warms up and seal cold.

A failing water pump with a slipping or worn impeller or clogged radiator is a suspect.

If you can't get the air bled out of the system I would suggest you remove the fan belt(s) and the thermostat crossover. Then start the engine and look for bubbles coming out of the coolant head ports. IMO 2 - 5 min should be enough and keep in mind the difference between bubbles and boiling. Bubbles indicate combustion gas leaks from: head gasket, head cracks, cylinder cracks. Sometimes it's just one side and you can concentrate repairs on that one side.

Tabs (coolant stop leak) make a mess in the radiator and are designed as a cheap band aid to kick the problem can down the road. (Cracked heads or blown headgaskets, but, general coolant leaks are what most would try and cure.) They might get you home from a bad adventure where you 'caught one in the radiator' and emergency repairs to get home. Bad advice if you wish to fix it properly long term the first time. Worse they somewhat cover up the problem so you can't diagnose it as easy.

H1 Hummer owners can better comment on the ECT of 220-230 due to the radiatror angle making it difficult to cool. The military treats these engines as expendable thus don't care about turning rings to slag temps. From pickups and SUV's the upper limit is 210 back off - 220 pull over. Rings turn to blowby and cracks are more likely to appear at higher ECT than 210.
 
WarWagon said:
Many things could be going on here. How long have you owned this and how many miles on it? New to you and you are discovering why they sold it? 🤪

Pictures can help answer questions. First a picture of the fan clutch so we can see what kind you have. How old is the fan clutch? I ask as a "root cause" question.

Holding pressure is a good sign. I would suspect the radiator cap is having trouble. Pressure test it. I have had poor quality caps and radiators not release pressure, then blow off suddenly shock cooling the engine, and then suck the hoses flat. I have seen cracked heads tend to leak as the engine warms up and seal cold.

A failing water pump with a slipping or worn impeller or clogged radiator is a suspect.

If you can't get the air bled out of the system I would suggest you remove the fan belt(s) and the thermostat crossover. Then start the engine and look for bubbles coming out of the coolant head ports. IMO 2 - 5 min should be enough and keep in mind the difference between bubbles and boiling. Bubbles indicate combustion gas leaks from: head gasket, head cracks, cylinder cracks. Sometimes it's just one side and you can concentrate repairs on that one side.

Tabs (coolant stop leak) make a mess in the radiator and are designed as a cheap band aid to kick the problem can down the road. (Cracked heads or blown headgaskets, but, general coolant leaks are what most would try and cure.) They might get you home from a bad adventure where you 'caught one in the radiator' and emergency repairs to get home. Bad advice if you wish to fix it properly long term the first time. Worse they somewhat cover up the problem so you can't diagnose it as easy.

H1 Hummer owners can better comment on the ECT of 220-230 due to the radiatror angle making it difficult to cool. The military treats these engines as expendable thus don't care about turning rings to slag temps. From pickups and SUV's the upper limit is 210 back off - 220 pull over. Rings turn to blowby and cracks are more likely to appear at higher ECT than 210.
Click to expand...
I changed the water pump and the clutch and put new radiator and a new cap . But still have the same problem . I just bought the truck in an auction so I only had it for like a month . So I wouldn’t know the reason they sold it but o was told it was a divorce auction
 
Pull the thermostat, shove a straw in it, and put it in a pot of water with a thermometer in it. Heat it up and see if it opens around 195-200 degrees. It may be sticking or you replaced it already? I have seen em installed backwards...

And since you are there... I would pull the fan belts and tstat crossover and check for bubbles (combustion leak) while warming the engine up some. Again at idle and don't get it too hot. These engines don't generate that much heat at idle.

Auction is what it is, no other info is reliable, and no longer matters. Unless you can chat with the prior owner. Not relevant to solving the problem.

Doesn't apply so much to the parts you changed, but, keep in mind new parts don't mean good parts. My example above was of a new radiator and cap. Regardless where did you get the fan clutch, brand, etc. This is a long term question you may be able to "refund" now and get a better one. We are frugal on here and lean toward diagnosis rather than throw parts at it due in part to "no quality" defective parts out there.
 
WarWagon said:
Pull the thermostat, shove a straw in it, and put it in a pot of water with a thermometer in it. Heat it up and see if it opens around 195-200 degrees. It may be sticking or you replaced it already? I have seen em installed backwards...

And since you are there... I would pull the fan belts and tstat crossover and check for bubbles (combustion leak) while warming the engine up some. Again at idle and don't get it too hot. These engines don't generate that much heat at idle.

Auction is what it is, no other info is reliable, and no longer matters. Unless you can chat with the prior owner. Not relevant to solving the problem.

Doesn't apply so much to the parts you changed, but, keep in mind new parts don't mean good parts. My example above was of a new radiator and cap. Regardless where did you get the fan clutch, brand, etc. This is a long term question you may be able to "refund" now and get a better one. We are frugal on here and lean toward diagnosis rather than throw parts at it due in part to "no quality" defective parts out there.
Click to expand...
New thermostats
 
The air is most likely combustion gas and thus the "quick and dirty" suggestion to watch the head coolant ports for bubbles with the crossover off. No bubbles mean you have a diffrent problem with coolant flow to chase. Bubbles can turn into pulling a or both heads or engine replacement depending on where the failure is.

@Will L. may have some other H1 specific ideas like a air purge procedure that doesn't apply to pickups.
 
WarWagon said:
Many things could be going on here. How long have you owned this and how many miles on it? New to you and you are discovering why they sold it? 🤪

Pictures can help answer questions. First a picture of the fan clutch so we can see what kind you have. How old is the fan clutch? I ask as a "root cause" question.

Holding pressure is a good sign. I would suspect the radiator cap is having trouble. Pressure test it. I have had poor quality caps and radiators not release pressure, then blow off suddenly shock cooling the engine, and then suck the hoses flat. I have seen cracked heads tend to leak as the engine warms up and seal cold.

A failing water pump with a slipping or worn impeller or clogged radiator is a suspect.

If you can't get the air bled out of the system I would suggest you remove the fan belt(s) and the thermostat crossover. Then start the engine and look for bubbles coming out of the coolant head ports. IMO 2 - 5 min should be enough and keep in mind the difference between bubbles and boiling. Bubbles indicate combustion gas leaks from: head gasket, head cracks, cylinder cracks. Sometimes it's just one side and you can concentrate repairs on that one side.

Tabs (coolant stop leak) make a mess in the radiator and are designed as a cheap band aid to kick the problem can down the road. (Cracked heads or blown headgaskets, but, general coolant leaks are what most would try and cure.) They might get you home from a bad adventure where you 'caught one in the radiator' and emergency repairs to get home. Bad advice if you wish to fix it properly long term the first time. Worse they somewhat cover up the problem so you can't diagnose it as easy.

H1 Hummer owners can better comment on the ECT of 220-230 due to the radiatror angle making it difficult to cool. The military treats these engines as expendable thus don't care about turning rings to slag temps. From pickups and SUV's the upper limit is 210 back off - 220 pull over. Rings turn to blowby and cracks are more likely to appear at higher ECT than 210.
Click to expand...
Someone told me to take the thermostats out because I live in Florida and it’s always hot
 
John hanna said:
Someone told me to take the thermostats out because I live in Florida and it’s always hot
Click to expand...

The thermostats are not the problem here. (Unless defective and not sure the duals can be installed backwards.)

I live in extreme heat Phoenix AZ that can make Florida look like a winter day. I did run a "summer" lower ~185 degree T Stat. Colder places at altitude in the winter I would run a OEM 195 degree. Some say better MPG with the OEM stats. Diesel engine efficiency is all about being in the proper temperature range.

That said: HAHA! Snort! this old wives tale of remove em is still going around...

If removing them masks the symptoms it may buy you time. Odds not that great for the entire engine, however, correcting the problem early if it's a cracked head or blown heads gasket can allow the longblock (bottom end) to last longer. You may have an improved Navistar cast or Optimizer engine in there if it was ever replaced in the past or what was being produced or in stock when your H1 was rolling down the assembly line. (I am lazy and didn't look up specifics for your year.) By odds I mean these disposable and expendable engines like to crack the #8 cylinder. That doesn't mean it isn't a simple cracked head or head gasket. Just saying the odds of tearing into the engine for head gaskets is more likely to have you remove and replace the entire engine. So expect the worst and hope for the best.

Regardless so far the best advice now is troubleshooting looking for a combustion leak so you can decide what is needed to: fix it, quietly dump it back on the market, or run it till it blows and then drop another engine in it.
 
Welcome.

Gonna pm you my phone number but today is wife’s bday, so try me tomorrow 8 pm your time.
So, there is a ton of misinformation out there about hummers and the 6.5. 95% of the 6.5 info on this forum is gold. The hummer forums are good for body, suspension, interior, etc but junk on engine/transmission.

You will not get the hummer where it is a rig that doesn’t get worked on. They are engineered to have frequent maintenance. If you can afford better tools to make jobs easier it becomes a game changer. Expect $1200 in speciality tools for it if you diy. Ifyou pay a mechanic not equipped specific for hummers, you can save half that.

Bleeding air out of our cooling system is a pain. Mightyvac mv4525 is $200ish on Amazon.

Before ordering it though, follow WarWagon’s comment. Remove fan belt. Remove the thermostat crossover from the engine and DO NOT drain the coolant before doing it, just let it spill (5 gallon catch bucket for mess good idea). Then start the engine and Watch the 2 coolant ports where the crossover attached to the heads. If it starts bubbling air out, a head is coming off and high possibility the block is cracked. Put a thermometer in the passenger side head where the water is and when it gets 205f and still no bubbles- shut it off and dance a happy dance. Bubbles = engine coming out.

At that point of no bubbles, then order the tool to save years of headaches imo.

Big fat lies are told that temps of 225 and above are ok- if you EVER hit 220 pull over and at 225 shut it off and wait 1/2 hour- period. If it is so important you keep driving, just know you are spending $5,000-$10,000 to do it.

Tabs are option but do the diagnostics first. They are a bandaid.
 
As far as removing "T" stats, I only ever did it on a 69 Mustang, it over heated 10 times worse than the stuck "T" stat did. I don't think the coolant has time to cool. IDK, just my experience.
 
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