What's a normal temperature for H1?
 

My H1 runs around town at about 200f. When on freeway it goes up and down from 215-225f.

I have added a large fan on the radiator and hood scoops on the grill to direct airflow better and added "water wetter" additive with no help.

When I am towing my boat, temp gets to 225-245f. Is this OK? Normal?

I feel like I am looking at my temp gauge every minute with no relaxation, as twice I have over heated due to a blown heater core leaking all over my floor board and a blown heater control valve. The valve was new and literally one of the inlet tubes melted off and my coolant left! I have now installed gas line shut off valves before and after the heater control valve so I can bypass them in an emergency.

Any tips would be great! Thanks.

Is your fan shroud sealed? If the stack (radiator, oil cooler, AC) isn't properly sealed then all the air you are blowing through it isn't doing its job. The shroud needs to be solid and there is some insulation around the stack area that makes sure the air doesn't leak around and insures it gets pulled through the fan.

Are you sure you don't have any air bubbles in the engine? If the antifreeze was changed were all the stops taken out to allow all the air out?

Well, my AC is ice cold. So I assume the fan shroud is sealed.

I get hot heat too, so I assume my coolant is circulating fine...

Would like to know if my temps are normal. To go from 200f-245f seems like a large range...

My normal running temperatures for my 6.5TD are 185F - 205F. Even going 65mph on the highway in 90F summer heat, I don't see it go much above 205F. I haven't towed anything larger than my jet ski, so I cannot comment on towing temperatures, but it should be slightly elevated. I don't believe 225-245F is right though.

- Check your radiator stack. Disassembly will probably reveal much dirt / debris / leaves between the radiators blocking air flow.

- Check your thermostats. There are two. Sometimes if one fails to open you'll have elevated engine temperatures.

- Check the shroud to ensure it is sealed.

- Purge all air from the coolant system. The H1 can get air trapped easily and cause the exact symptoms you are describing.

X2 on the above post

Thanks for the feedback, I guess mine is running hot...

1. I have had both thermostats replaced already.
2. I have had radiator flushed recently.
3. I have mounted a large fan on top of my stacks and mounted hood scoops over them to direct airflow. I did this to increase AC.

It has always ran at about 200-205 around town and 220 on freeway. I just started to get concerned when it would reach 225-245 when towing my 20' boat.

I could try to bleed any air in the cooling system, any tips on how to do it myself?

Thanks.

Here's the bleed 101 guide over at The Hummer Network.
The Hummer Network :: Log in

Have you made sure that your cooling stack is clean? I have seen a lot of them with the fins packed with mud and leaves on the underside.

that was just some login to a hummer calender?!?!

If you register an account there, you can view the link. I highly suggest registering there.. they have a more active H1 community than here, and there's a lot of good how-to guides and troubleshooting guides.