Poor ventilation/truck overheating?

[Michael1]

Originally Posted by ketcat

From what I understand it is a common problem in this area and Jay at Lund Hummer is working on a larger aluminum radiator for the H3.

No need for a larger radiator. It's not overheating under load. The problem is at low speeds, when there is low air flow. Best solution would be an electric pusher fan. I've noticed the A/C isn't the greatest at low speeds on hot days, too, so an electric fan would help there, too. It is too bad GM didn't include one, because then it could be programmed to turn off with higher vehicle speeds.

A larger (deeper radiator) will reduce A/C performance, because of the additional air restriction, unless they reduce the fin count, which would negate the extra depth.

Michael

[Ipedog]

This sounds like a problem in the cooling system, not a normal condition.

The last time at Paragon we had all been spashing through mud for days and the trucks were completely coated. I know that my radiator had lots of crap in it. We were running a long crawler of a trail and it was HOT (see pic below) and the truck never got to the H. Both HIHUMMER and I were on the same trail and noticed the same conditions.

It sounds like your dealer isn't trying hard enough to figure out what the issue is.

It was a wee bit warm...

[ChevyHighPerformance]

Did the dealer independently check the engine temps (i.e., separate thermometer)? Could your engine coolant temperature sensor be bad?

[f5fstop]

As Chevy High Performance states...is it the coolant, or is it the gage, but more importantly, is it the sensor. If the gage is bad, the A/C should not shut off, but if the sensor is bad, the signal from the PCM to the BCM will trigger the BCM to shut down the A/C. In addition, the PCM, controls the coolant gage, and if the sensor is showing hot, the PCM shows hot on the gage.
They can check the coolant temp via a thermometer and verify the sensor via the Tech 2.

Has the dealer checked the fins in the radiator, checked the passages?


If this fails, request the dealer do a complete drain and then perform a vac-and-fill procedure. On some engines (especially inline), there has been problems with large air bubbles causing overheating problems, usually localized to that are of the engine. The vac-and-fill method prevents air bubbles from forming. This condition can come from the plant if during fill the storage tank was switched for the coolant/water mixture.

If this is not the problem, I would say you have a restriction. Airflow is ok through the compartment at speeds, and the mechanical fan does a good job of drawing air, and believe it or not, weighs in less than a electrical fan setup. (Weighed one versus an electrical setup for the infamous H3Lady last year ).

What you describe is not normal. Mine in up to 90 degree weather has remained just below the 1/2 mark.

[ketcat]

Originally Posted by Michael1

No need for a larger radiator. It's not overheating under load. The problem is at low speeds, when there is low air flow. Best solution would be an electric pusher fan. I've noticed the A/C isn't the greatest at low speeds on hot days, too, so an electric fan would help there, too. It is too bad GM didn't include one, because then it could be programmed to turn off with higher vehicle speeds.

A larger (deeper radiator) will reduce A/C performance, because of the additional air restriction, unless they reduce the fin count, which would negate the extra depth.

Michael

As I'm sure you know (sounds like you are mechanically inclined) if you ask three different engineers about cooling system theory you will get three different answers. Bigger radiator, offset rows, different fin designs, different coolant, coolant flow direction, fans etc..... Lot's of race teams are using the SMALLEST radiator they can run without overheating on the track.

The fact is any stock car should be able to idle in 110 (even 120) all day with the A/C on and never overheat or getting hot.

Because it appears to be a problem with most H3's in this area I thought it would be important for people to know someone is looking at one possible solution.

Personally mine has not overheated but if it did I would make the dealer fix it and if they didn't I would get GM involved.

[Michael1]

Originally Posted by ketcat

As I'm sure you know (sounds like you are mechanically inclined) if you ask three different engineers about cooling system theory you will get three different answers. Bigger radiator, offset rows, different fin designs, different coolant, coolant flow direction, fans etc..... Lot's of race teams are using the SMALLEST radiator they can run without overheating on the track.

The fact is any stock car should be able to idle in 110 (even 120) all day with the A/C on and never overheat or getting hot.

Because it appears to be a problem with most H3's in this area I thought it would be important for people to know someone is looking at one possible solution.

Personally mine has not overheated but if it did I would make the dealer fix it and if they didn't I would get GM involved.

You are absolutely right about this. Cooling system design is a bit of balancing act, and black art. You want a big, deep radiator with a lot of fins, plenty of tubes, but not too deep and not too many fins and tubes such that it restricts air flow. You can change the pitch and number of fan blades. You can change the clutch cut-in temperature, and fan rpm. GM runs a lot of tests on cooling systems to try to strike the best balance, including cooling system performance, A/C performance, fan noise, and fan load. I am a little surprised the cooling system seems a bit marginal at low speeds and high temperatures on a vehicle designed for rock crawling, but I wasn't there when they came up with the compromises stated above. I wouldn't mind hearing what people's trailer towing experiences have been in hot weather. That is one of the most difficult tests to pass.

I was only suggesting the pusher fan, because it would probably be less expensive than a custom radiator, and so far the problems have been reported at low engine and vehicle speeds. I also thought the A/C performance was marginal at low engine and vehicle speeds, and an electric fan would help that condition, too. My experience is the H3 cools down quickly as soon as engine speeds are brought up.

Michael

[deserth3]

One item I haven't seen mentioned here is the lower radiator hose. It should have a spring in it to keep it from colapsing. Easily checked by squeasing the hose.

[ketcat]

Michael

We are on the same page, especially about the fan and the a/c performance. Wasn't R12 a wonderful thing? Ice cold A/C no matter what.

PS: It's 109 outside, my H3 has been idling on asphalt int he sun for about 45 minutes with the a/c on and the gauge is at 3/4. The day that mine got hot I think it was 114. I have a Tech II in the shop but don't have a candi module so I can't track temps. If I can use a friends candi module I will track the temps and see what happens. If I really get ambitious I will hook up the data logger.........we'll see.

Excellent cooling system chat by the way, thanks.

Ken

[Michael1]

Originally Posted by ketcat

Michael

We are on the same page, especially about the fan and the a/c performance. Wasn't R12 a wonderful thing? Ice cold A/C no matter what.

PS: It's 109 outside, my H3 has been idling on asphalt int he sun for about 45 minutes with the a/c on and the gauge is at 3/4. The day that mine got hot I think it was 114. I have a Tech II in the shop but don't have a candi module so I can't track temps. If I can use a friends candi module I will track the temps and see what happens. If I really get ambitious I will hook up the data logger.........we'll see.

Excellent cooling system chat by the way, thanks.

Ken

Ken,

How about R12, and a GM swash plate 6 cylinder non-cycling compressor? Comfy!

109F, idling, and gauge at 3/4 doesn't sound too bad. Which direction was the nose pointed relative to the wind? It would be interesting to pin down the conditions where these things are getting hot. I was at the Hummer Happening near Los Angeles in the Santa Monica Mountains, and temps were low 90's. I was watching the guage closely, because of the overheating reports. One minute the guage was just below the red zone, and the next it was mid-point, even when just idling with the air on. Seems like something isn't quite right.

Michael

[ketcat]

Originally Posted by Michael1

Ken,

How about R12, and a GM swash plate 6 cylinder non-cycling compressor? Comfy!

109F, idling, and gauge at 3/4 doesn't sound too bad. Which direction was the nose pointed relative to the wind? It would be interesting to pin down the conditions where these things are getting hot. I was at the Hummer Happening near Los Angeles in the Santa Monica Mountains, and temps were low 90's. I was watching the guage closely, because of the overheating reports. One minute the guage was just below the red zone, and the next it was mid-point, even when just idling with the air on. Seems like something isn't quite right.

Michael

The "good old days" when you could hang a side of beef in your car.... Oh well I guess DuPont made out on the R12 to 134 switch.... Just joking I know why the EPA made us switch and A/C in newer cars actually works pretty well, in fact one of the things I like about the H3 is how well the A/C works. I'm sure the relatively low heat load due to the small glass area helps.
Interesting question about the wind direction.
The other day when it was 109 and the gauge stopped at about 3/4 (I agree 3/4 on the gauge is not a concern) the wind was blowing about 5 to 10 mph and was hitting the vehicle on the drivers front (i.e. if the H3 was facing north the wind was coming from the north west). Today the temp was about 107 and there was no wind. After idling for about 10 min the gauge was past 3/4 which was surprising until I read your e mail. Just for fun I'm going to have the guys in the shop throw a 14" Spal fan on it and see what happens.