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Old 08-10-2019, 01:12 AM   #1
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Default Chevy Express 3500 overheat and stall - mountain road

Last week we were driving our 2003 Chevy Express 3500 Roadtrek 190P up to Sequoia NP - a steep, curvy, long road with a lot of altitude gain. Shifter in second gear. I was keeping my eyes on the coolant temp - I swear it never got over 3/4 up the gauge. Engine started loosing power, and after about a minute or two of worsening power, the engine just stopped. Check engine light came on as the motor did the final wheeze. In the lane on a tight two-lane mountain road, with nowhere to pull over. Starter would not engage or make any sound. Opened the hood, and it was really hot under there, but not the smoky, gurgling, steaming sort of hot I'd expect of an engine overheat. Let it cool for maybe 5 minutes, and it started up, made it about a quarter of a mile, and croaked again. Waited 5 minutes, made a u-turn, and headed back downhill. Never made it to Sequoia, and didn't have any more trouble on the rest of the trip - 700 miles.

Check engine code was for a misc misfire, no limp-home or other computer codes where the computer may have recognized a problem and did something about it.

I'm having a hard time believing that this was an engine coolant overheat, it wasn't feeling like that under the hood. My only crazy thought is that the transmission got so hot that it caused heat soak and engine electricity stopped flowing. Might explain the starter not doing anything. Transmission fluid was low. I'm having the tranny serviced and adding an external transmission cooler just because.

We've put 10,000 miles on this vehicle, been to Yosemite twice, and over the Sonora pass without any trouble. I spoke to my mechanics and a transmission guru, and they are stumped.

Anybody experienced something like this? I really need to figure this out - it was a pretty scary experience.

Thanks!
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Old 08-10-2019, 01:48 AM   #2
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Originally Posted by rauscs View Post
Last week we were driving our 2003 Chevy Express 3500 Roadtrek 190P up to Sequoia NP - a steep, curvy, long road with a lot of altitude gain. Shifter in second gear. I was keeping my eyes on the coolant temp - I swear it never got over 3/4 up the gauge. Engine started loosing power, and after about a minute or two of worsening power, the engine just stopped. Check engine light came on as the motor did the final wheeze. In the lane on a tight two-lane mountain road, with nowhere to pull over. Starter would not engage or make any sound. Opened the hood, and it was really hot under there, but not the smoky, gurgling, steaming sort of hot I'd expect of an engine overheat. Let it cool for maybe 5 minutes, and it started up, made it about a quarter of a mile, and croaked again. Waited 5 minutes, made a u-turn, and headed back downhill. Never made it to Sequoia, and didn't have any more trouble on the rest of the trip - 700 miles.

Check engine code was for a misc misfire, no limp-home or other computer codes where the computer may have recognized a problem and did something about it.

I'm having a hard time believing that this was an engine coolant overheat, it wasn't feeling like that under the hood. My only crazy thought is that the transmission got so hot that it caused heat soak and engine electricity stopped flowing. Might explain the starter not doing anything. Transmission fluid was low. I'm having the tranny serviced and adding an external transmission cooler just because.

We've put 10,000 miles on this vehicle, been to Yosemite twice, and over the Sonora pass without any trouble. I spoke to my mechanics and a transmission guru, and they are stumped.

Anybody experienced something like this? I really need to figure this out - it was a pretty scary experience.

Thanks!

Your experience actually sounds somewhat familiar to what we found on our 07 Chevy Roadtrek. Ours happened in a second and third gear climb in Rocky Mountain Nat Park.


I think there is one scenario you don't know about, and neither did we at the time. All kinds of things happen at about 240* for mostly the trans, but also for the engine. Our testing would indicate it probably was the transmission that stalled you and not necessarily because it made the engine too hot. The stock programming on the transmission allows for no torque converter lockup in first gear, and second gear will not lock until something like 50 mph at full throttle, so both of those gears are useless for climbing mountains in most cases, if you need the converter to lock to reduce heat generation. Third gear will not lock until about 60 mph so also won't ever be locked when climbing. Unlocked torque converters generate huge heat and the trans cooling is in the radiator so it heats up the water besides and make the engine hot.


Now, what will stop you all of a sudden and essentially kill the engine. What the transmission computer does is look at the trans temp sensor and when it hits about 240*, it will essentially lock the torque converter to prevent further heat gain, in all gears, almost 100% of the time. If you happen to be climbing a mountain in a lower gear and the converter suddenly locks, you have just lost maybe 25+% of your climbing horsepower and you just plain stop because the engine is already at max. It is frightening, because you are suddenly done, no power, no coasting because you are going up a steep hill. It totally irritates everyone behind you.


We have experimented with all the various available "fixes" for the cooling including add on fans, add on trans coolers, radiator airflow baffling, different grille to let in more air, separating trans and water cooling, bigger radiator. They all helped, some more than others, but what finally made it all much better was getting a programmer/tuner for the van that allowed me to reprogram the shift points and torque converter lockup speeds. By optimizing them for climbing situations in the tow/haul mode, the heating issue pretty much went away completely, but we had most of the other changes already in place also.



I can say that with all of the stuff done, we rarely if ever see a trans or water temp over 200* under nearly all conditions. And that is without the extra cooling fans on so have them in reserve.


Almost all of this is documented on this forum, along with what others have done, so certainly worth a read, I think.


IMO, there is no reason for any vehicle that is loaded within spec to run hot, but sometimes the cure is tough to find.


Good luck with your van and getting it cool, as it is nice once done.
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Old 08-10-2019, 02:55 AM   #3
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Booster, you ARE the man. I remember seeing something like this trans re-program, but glossed it over because it did not pertain to me at the time. I'll dig around and learn.

Thanks!
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Old 08-10-2019, 01:59 PM   #4
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Rauscs, Booster,
This is very timely for me as I am contemplating a trip to Rocky Mountain NP and Seqouia in about 5 weeks in my 2006 RT 210.

My 210 was supposed to have the auxiliary transmission cooler according to the GM build sheet but it did not. I added a cooler with a fan and on-off switch. It is located after the radiator cooler. In our out-west trip 2 years ago it did fine with tran temps (from a Scangage) typically 160-170 and then 200-215 on a long steep climb at Great Basin NP and a few others. I think RMNP or the Sequoia climb will stress the cooling system even harder. Rauscs: do have the auxiliary cooler?

Read through booster's post on the tuner. That sounds like the best upgrade to handle tough climbs. Looks like it is pretty involved to make the adjustment settings but maybe I am thinking it is more complicated than it is.

http://www.classbforum.com/forums/f8...icks-7158.html

Started poking around on the internet and came upon this post. A few had installed a manual torque converter lockup switch to use when climbing. I am not sure how that is setup but it sounds like a possible “poor man’s” way to get lockup when you need it. Seems like a big risk would be forgetting to unlock the TC when you shifted gears.

https://www.dieseltruckresource.com/...towing-318701/
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Old 08-10-2019, 02:37 PM   #5
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Rauscs, Booster,
This is very timely for me as I am contemplating a trip to Rocky Mountain NP and Seqouia in about 5 weeks in my 2006 RT 210.

My 210 was supposed to have the auxiliary transmission cooler according to the GM build sheet but it did not. I added a cooler with a fan and on-off switch. It is located after the radiator cooler. In our out-west trip 2 years ago it did fine with tran temps (from a Scangage) typically 160-170 and then 200-215 on a long steep climb at Great Basin NP and a few others. I think RMNP or the Sequoia climb will stress the cooling system even harder. Rauscs: do have the auxiliary cooler?


Read through booster's post on the tuner. That sounds like the best upgrade to handle tough climbs. Looks like it is pretty involved to make the adjustment settings but maybe I am thinking it is more complicated than it is.

http://www.classbforum.com/forums/f8...icks-7158.html

Started poking around on the internet and came upon this post. A few had installed a manual torque converter lockup switch to use when climbing. I am not sure how that is setup but it sounds like a possible “poor man’s” way to get lockup when you need it. Seems like a big risk would be forgetting to unlock the TC when you shifted gears.

https://www.dieseltruckresource.com/...towing-318701/

Peteco is exactly right on the tuner as it is not for the feint of heart and does really need be done by someone with some background in how the the transmission actually work and why they are programmed as they are.

That said, with the information in the programming thread, it is pretty likely you would be able to find a high performance shop that could do the reprogram the trans for you. I did talk to a couple of shops that could do it, before I bought the tuner, but they did not have any experience in programming for reducing heat issues. If they were shown the printouts of what has worked for us, I think they would see what the goals were readily.

For those of us with the older units, not sure where the cutoff is, there is also a programming "oddity" that comes into play on really, really steep climbs. These would be the ones that require low gear, so there is no chance to have it ever be locked converter as it is not allowed, probably for torque reasons. With ours, we would put the selector in "1" position and move out in low gear up such climbs, which are usually quite short. You need low gear to get up it, and the higher the rpm (speed) in low gear the better for coolant flow and converter efficiency. All would be good until something like a curve where I would have to let off the throttle. As soon as I did and them opened the throttle again, the van would not reaccellerate, slowing down with trans temp shooting up. What I found with the scanner part of the tuner is that even in "1" the trans would follow the same shift pattern as it would in drive for first and second gear, so it was shifting into second when I let off, and would not go back in to low until nearly stopped. We got stalled on those type climbs several times before I got the tuner and found it. Originally, I couldn't do much except change the shiftpoint out of the way, but the interfered with other types of driving. By then others (autocrossers) had also found the glitch and were able to pressure the tuner maker to do an update to add the ability to eliminate the shift out to second. Works great now.


Manual lockup converters are a really bad idea unless you have a full manual valve body in the trans so it never shifts on it's own. If it shifts with the converter locked, it will likely work for a while, but it is very, very, hard on parts especially if it shifts at full torque load.


The best manual locking setting converter setups I have seen used a floor mounted shifter that had ever gear interlocked so a button had to be pushed to move the stick. That button also interrupted the lockup clutch circuit to unlock it while shifting.

Funny think is that the tuner will allow you to shut off lockup cutout at shifts if you want, but they tell you not to do it. Apparently some racing types will accept the carnage to get faster, tighter, shifting.

There is now also a replacement piece for the torque converter lockup section clutch (IIRC) that will increase trans oil flow to the cooler. I will try to find it again. I don't know if it would help the problem unless you had huge add on coolers to handle the extra heat coming out with the improved flow, as currently it is the cooler that get overloaded either the radiator or addon. It would also require trans removal to put in, I think.
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Old 08-10-2019, 03:15 PM   #6
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Here is a link to the cooler flow improver product. This company seems to know their stuff, and it is worth a read of some of their tech pages, also. I don't know anyone who has used any of their stuff though.


https://www.sonnax.com/parts/1989-lu...egulator-valve
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Old 08-10-2019, 04:21 PM   #7
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Booster: any thoughts on a manually controlled TC lockup switch?
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Old 08-10-2019, 04:28 PM   #8
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Booster: any thoughts on a manually controlled TC lockup switch?
Hi Pete,

I'm not Booster : ) , but I looked into this for my 09/10 RT 190P, and the necessary connections at the OBDII port weren't there (or anywhere else I could find). YMMV on your older chassis.

Good luck, Dick
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Old 08-10-2019, 06:07 PM   #9
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Great feedback, all - thanks!

Booster - are the tuner tables shown in your 12/2017 posting in the "Teach your old Chevy new tricks?" thread the most recent, or have you made more changes since then? I'm thinking I'd just change my Tow/Performance settings to match yours.

peteco - I don't have an external cooler yet, but will on Monday!

I have been using an "Ultragauge", which is a lot like the Scangauge that Booster mentions. I had to order a new one, because the Chevy transmission temp is not one of the gauges available in the standard Ultragauge. I ordered the "XM" version, which allows you to program in brand specific codes.

I've already upgraded the radiator to the version that Booster suggested.
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Old 08-10-2019, 06:17 PM   #10
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Originally Posted by rauscs View Post
Great feedback, all - thanks!

Booster - are the tuner tables shown in your 12/2017 posting in the "Teach your old Chevy new tricks?" thread the most recent, or have you made more changes since then? I'm thinking I'd just change my Tow/Performance settings to match yours.

peteco - I don't have an external cooler yet, but will on Monday!

I have been using an "Ultragauge", which is a lot like the Scangauge that Booster mentions. I had to order a new one, because the Chevy transmission temp is not one of the gauges available in the standard Ultragauge. I ordered the "XM" version, which allows you to program in brand specific codes.

I've already upgraded the radiator to the version that Booster suggested.

It sounds like you are well on your way to getting this straightened out. I think you will find the radiator to be a big plus especially when combined with a big add on trans cooler.



I think there have probably been some tweaks since then, but I will have to look. One would probably be the low gear lock issue I mentioned earlier. If you do decide to do the changes, you are very wise to use the tow haul only as you just shut it off and be back to factory normal drive. It is what I did with all the early testing. Surprisingly, I think, is that for climbing big hills, the tow haul is actually programmed worse from the factory than the normal program as it raises the speed for lockup an shifts even higher than normal. If you decide to do the changes I will offload our existing setup and should be able to send it to you as a file. The program itself has always been free from HPTuners, so you would be able to read the file without issue or spending any money if that is still the case. You only would then have to pay someone to do it for you or buy the tuner and license.


Good luck with your quest, we will be waiting for information on how it all worked out for you.
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