Chevy Express 3500 overheat and stall - mountain road

[rauscs]

Hi John, Thanks for the detailed response. Kinda makes my story seem like a walk in the park. I'll check out the service bulletin. My first idea was that altitude had something to do with the problem, but didn't find anything that mentioned that.

I just installed an Ultragauge XM (nice device) and set it up to show engine and transmission temp, and installed an external transmission cooler. My plan at this point is to keep an eye on those temps and stop to cool down before things go sideways. After reading your response, I may replace the fuel pump as well.

[Bud]

Originally Posted by rauscs

Hi John, Thanks for the detailed response. Kinda makes my story seem like a walk in the park. I'll check out the service bulletin. My first idea was that altitude had something to do with the problem, but didn't find anything that mentioned that.

I just installed an Ultragauge XM (nice device) and set it up to show engine and transmission temp, and installed an external transmission cooler. My plan at this point is to keep an eye on those temps and stop to cool down before things go sideways. After reading your response, I may replace the fuel pump as well.

The problem is 'vapor lock' with the fuel. The fuel will vaporize at a lower temperature with altitude And fuel temperature - a combination.

[rtbill]

We had a very similar experience in 2002 with our '01 200, also in New Mexico. The engine progressively lost power. We limped the last few miles to Santa Fe on the shoulder, and barely coasted into the Santa Fe Chevy dealer a little before they closed for the weekend. The diagnosis was the fuel pump, which had to be ordered. That fixed the problem and we haven't had similar trouble since. The repair was covered by the warranty. We spent almost a week living in a motel and lost some of our food because the dealership would not understand the van had to remain plugged into shore power for the refrigerator.

[rauscs]

FYI Searching this forum for the service bulletin#05-06-04-046A brings up another related thread.

[rauscs]

We went to Yosemite last week and on the way up the hill the trans temp got up to 263 - and I pulled over to cool down. Engine/trans did not act up at all.

How hot is too hot for the transmission? I picked 260 to stop for no real reason other than it sounds like 240 is when the computer starts making changes due to heat.

I have not made the transmission programming changes yet because of the $$. I was hoping to keep an eye on the temp and pull over to cool - but now I'm not sure when to do that.

[booster]

Originally Posted by rauscs

We went to Yosemite last week and on the way up the hill the trans temp got up to 263 - and I pulled over to cool down. Engine/trans did not act up at all.

How hot is too hot for the transmission? I picked 260 to stop for no real reason other than it sounds like 240 is when the computer starts making changes due to heat.

I have not made the transmission programming changes yet because of the $$. I was hoping to keep an eye on the temp and pull over to cool - but now I'm not sure when to do that.

The stock program for our van shows a "hot" signal at 267* and release the hot signal at 264*, but ours seemed to trigger a bit lower than that at probably 245* or so. I didn't have the tuner then so was going be the Scangauge which was climbing very quickly at that point. It would go into full converter lockup on ours and thus loose climbing power. At 260* you are way hot IMO, and if you don't have Dexron VI in it probably cooked the trans oil so it would need to be changed. Even with Dex VI that is right at it's high limit. The factory started using Dex VI in 2007, it appears, in the vans.



The question that goes along with this is how hot was the engine coolant at that point, as the trans fluid goes through the radiator also (unless you took it out when adding the cooler). I found that once the radiator got maxed out, both temps kind of climbed together, so could easily have been near 250*+ on the water, which is also way hot.


We never ran ours with the reprogramming done and stock radiator, fan, and trans cooling in the radiator, so hard to tell where it would run that way, but with all the stuff we did we did not go over 200* on the water or trans on the same climbs we got so hot on before. Dicktill is running his reprogram on all stock stuff, so would be a better source on that.


What speed and rpm were running at as it got hot? That information may allow me to look at the program and figure out if the converter was locked or unlocked.

[SteveJ]

Originally Posted by rauscs

We went to Yosemite last week and on the way up the hill the trans temp got up to 263 - and I pulled over to cool down. Engine/trans did not act up at all.

How hot is too hot for the transmission? I picked 260 to stop for no real reason other than it sounds like 240 is when the computer starts making changes due to heat.

I have not made the transmission programming changes yet because of the $$. I was hoping to keep an eye on the temp and pull over to cool - but now I'm not sure when to do that.

I agree on the fluid change if Dexron VI is not currently installed, new transmissions are not cheap and any inferior/earlier oils will be burnt.

Something else to investigate is if your radiator fan clutch is engaging, does it start to roar when the temperature climbs? If so, at what temp?

I was seriously considering changing the torque converter lock up points but the new fan clutch helped enough to make trans heat much less of an issue.

I've changed over to Dexron VI in my 2000 Chevy. I pull over when the trans temp hits 225 which happens a lot less with a new severe duty fan clutch. I'm currently running the radiator heat exchanger and the factory trans cooler with a pusher fan in front of the trans cooler. Virtually all of my mountain grade pulling is with 2500lbs of trailer and cargo behind the van.

Also, I have a Turbo Fusion app on the phone that shows throttle position. I try to keep it at 50% throttle when climbing in lower elevations up to about 3-4,000' scaling to perhaps 60-70% when at 10,000'. The throttle position gauge is also quite helpful when trying to maintain torque converter lock up.

Turning off the A/C or at least to low fan speed also helps to avoid heat buildup.

[booster]

Originally Posted by SteveJ

I agree on the fluid change if Dexron VI is not currently installed, new transmissions are not cheap and any inferior/earlier oils will be burnt.

Something else to investigate is if your radiator fan clutch is engaging, does it start to roar when the temperature climbs? If so, at what temp?

I was seriously considering changing the torque converter lock up points but the new fan clutch helped enough to make trans heat much less of an issue.

I've changed over to Dexron VI in my 2000 Chevy. I pull over when the trans temp hits 225 which happens a lot less with a new severe duty fan clutch. I'm currently running the radiator heat exchanger and the factory trans cooler with a pusher fan in front of the trans cooler. Virtually all of my mountain grade pulling is with 2500lbs of trailer and cargo behind the van.

Also, I have a Turbo Fusion app on the phone that shows throttle position. I try to keep it at 50% throttle when climbing in lower elevations up to about 3-4,000' scaling to perhaps 60-70% when at 10,000'. The throttle position gauge is also quite helpful when trying to maintain torque converter lock up.

Turning off the A/C or at least to low fan speed also helps to avoid heat buildup.

The clutch fans come in several different styles that lock up and different temps so an HD one that locks lower, faster could certainly help. A fixed blade fan would likely do even better at the slower speeds of steep climbs. It takes a lot of heat to get most lockup fans to engage, probably 220-230* water temp on most of them, I think.



The lower throttle angles may or may not keep the converter from locking, but speed (really rpm but it programs as speed on the tuner) is needed for it to lock up even at lower throttle positions. If the low throttle position is costing you rpm capability, it might actually hurt temp rise.

Turning off the A/C or at least to low fan speed also helps to avoid heat buildup.

Even better shut off the AC, open the windows and turn on the heat full blast. It is surprising how much it can help.


Your year Chevy should be able to be a drop in the for 454/8.1 double core radiator, so that may also help.

[SteveJ]

Originally Posted by booster

The clutch fans come in several different styles that lock up and different temps so an HD one that locks lower, faster could certainly help. A fixed blade fan would likely do even better at the slower speeds of steep climbs. It takes a lot of heat to get most lockup fans to engage, probably 220-230* water temp on most of them, I think.



The lower throttle angles may or may not keep the converter from locking, but speed (really rpm but it programs as speed on the tuner) is needed for it to lock up even at lower throttle positions. If the low throttle position is costing you rpm capability, it might actually hurt temp rise.





Even better shut off the AC, open the windows and turn on the heat full blast. It is surprising how much it can help.


Your year Chevy should be able to be a drop in the for 454/8.1 double core radiator, so that may also help.

There is a difference between heavy duty and severe duty for fan clutches. I installed a Hayden SD clutch a couple of years ago that was pretty consistent at engaging at 208* coolant temp. It failed just out of warranty, it would not release. I replaced it with a "guaranteed for life" O'Reilly's brand a year ago. It kicks in at about 210-215 coolant temp, lower if in city traffic. A fan with an electric clutch would be preferable but this works "OK".

Those throttle positions come into play after losing torque converter lock up. As the engine is not an aviation or marine engine I'm a bit leery of putting more power to it except in short bursts like passing (and racing )

Agree on the heater at full blast. But if it's hot enough to need A/C I would rather pull over for a few minutes and cool things down than blast the heat, personal preference. I'm not generally in a hurry or drive too fast with the RT. Motorcycle is a whole other ball game as far as "too fast".

I'm sure the dual core rad would help quite a bit. If the current almost twenty year old rad goes bad it will get replaced by a dual core.

[rauscs]

Thanks to all for their input. I'll try to answer all of the questions...

I already have the larger radiator installed. The new trans cooler I put in bypasses the radiator trans cooler and stands alone. If I remember correctly, the water coolant temp was under 220 when the trans was at 263.

I'll ask my transmission guy what coolant he put in.

The first time the temp went up to 263 was in a twisty two lane road in the boondocks. I had tow/haul on, and had the shifter in second gear - speed roughly between 20 and 35.

I don't remember hearing the fan kick in, but I wasn't listening for it, and the water coolant was not too hot.

Sounds like I've got a new SD/HD fan in my future. Besides that and re-programming the shift table, any other suggestions?

[booster]

Originally Posted by rauscs

Thanks to all for their input. I'll try to answer all of the questions...

I already have the larger radiator installed. The new trans cooler I put in bypasses the radiator trans cooler and stands alone. If I remember correctly, the water coolant temp was under 220 when the trans was at 263.

I'll ask my transmission guy what coolant he put in.

The first time the temp went up to 263 was in a twisty two lane road in the boondocks. I had tow/haul on, and had the shifter in second gear - speed roughly between 20 and 35.

I don't remember hearing the fan kick in, but I wasn't listening for it, and the water coolant was not too hot.

Sounds like I've got a new SD/HD fan in my future. Besides that and re-programming the shift table, any other suggestions?

Thanks for the update, it certainly helps understand things.



The trans cooler as a standalone is likely not going to be able to cool the transmission adequately if it isn't locked up more. We went through the same thing and we had nearly 60K btu/hr worth of cooler on it. We did not get as hot as you did though, as we also have two big Spal pusher fans that catch the coolers and radiator. As reference, the two coolers we have cover probably over 1/3 of the radiator area, so you likely have nowhere near that much in yours.


The tow/haul is probably another part of the problem as it raises the lockup even higher than the too high settings in normal mode. I think even in normal mode you need to be nearly 50mph in second gear to get the converter to lock.


You may also want to take a look at sealing up some of the air bypasses around the radiator as a lot of air is wasted that comes through the grille and doesn't go through the radiator.