Sangster
Member
That's a very good point!
2007 GMC Yukon XL Denali 6.2 Overheating at a stand still
- Thread starter Bocaguy
- Start date
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Sangster
Member
Soooo....just in case it's helpful for anyone else.....
I flashed my Denali back to stock and checked fan trigger temps. When sitting idle with AC off, the fan kicks to HIGH when the coolant temp hits 230 and then kicks back down to LOW when the coolant temp gets down to 220. With my specific Blackbear tune, it's 225 for HIGH and 212 for LOW.
I'm going to move my Trucool 40k from in front of the AC condenser down in the lower bumper area. I'll also see if Blackbear will tweak my tune so that the fans go to HIGH at 215 and back to LOW at 205. I hate seeing that gauge go above the middle, which happens for mine at 217 degrees.
My trans temps are under control. I saw a max of 185 in stop/go traffic and coolant temps were 230. Normally, my trans temp is 145-165. I imagine I'll see a bit of increase with the Trucool down below the radiator where there's no fan pulling air through it. If it becomes a problem, I'll put a fan on it. I'll post up an update after.
I flashed my Denali back to stock and checked fan trigger temps. When sitting idle with AC off, the fan kicks to HIGH when the coolant temp hits 230 and then kicks back down to LOW when the coolant temp gets down to 220. With my specific Blackbear tune, it's 225 for HIGH and 212 for LOW.
I'm going to move my Trucool 40k from in front of the AC condenser down in the lower bumper area. I'll also see if Blackbear will tweak my tune so that the fans go to HIGH at 215 and back to LOW at 205. I hate seeing that gauge go above the middle, which happens for mine at 217 degrees.
My trans temps are under control. I saw a max of 185 in stop/go traffic and coolant temps were 230. Normally, my trans temp is 145-165. I imagine I'll see a bit of increase with the Trucool down below the radiator where there's no fan pulling air through it. If it becomes a problem, I'll put a fan on it. I'll post up an update after.
Pretty sure this is my exact problem.. I'll try to make a very long story as short as possible:
TL;DR took the comment about the side baffles
to heart.. checked my own vehicle after a LONG list of other attempts, and may have finally found my issue.
I have a 2008 2500 Yukon XL with the 6.0. I live in Arizona and was going to be towing a 29ft travel trailer all the way to Montana and back in June. I did all my normal road trip preparations (checking coolant, tires, brakes, etc) and hit the road.
According to a website my wife found, the most extreme elevation change in our trip is actually here in Az going from Phoenix to Flagstaff.. so I figure if I am going to run into cooling issues.. it would be there.
Made it to Flagstaff 0 issues. Got into Utah and forced into heavy stop/go traffic and I noticed our temps would start creeping up after 5-10 minutes of sitting.. while moving there were 0 issues.
Made it to Montana with no other issues (never had to sit in heavy stop/go traffic the rest of the way + outside temps were MUCH lower) While in Montana at my sisters house I changed out the t-stat, fan clutch, belt tensioner, and belts (I try to replace anything that is unkown to me at once whenever I do a repair.. just so I know what is new-ish and what isn't)
Truck ran great on the way home until that extreme elevation change around flagstaff again (there is a big mountain that you must pass going both directions) and I ran into extreme over heating on that climb to the point I had to pull over and wait 20 or so minutes to cool off. I finished the last 2-3 miles of that climb and just as I crested the hill I got the "engine hot" message again on the dash so I pulled into the rest stop and waited another 30 or so minutes.
I couldn't find anything blatantly wrong (coolant level was good, no leaks, fan was spinning, tstat was open and I could feel coolant in both upper/lower hose).. I got back on the road (now I was almost all downhill) and was able to baby the truck home with no further issues other than running warmer than I prefer (240 ish instead of 210)
After getting home I found a hairline crack in the plastic of my radiator.. a quick search online told me that location is prone to breaking when the system is over pressurized (usually clogged radiator).
I put in a new radiator and water pump (I always do these in pairs.. makes me feel better) and I continue to overheat at idle/stopped. When moving there is 0 issues.
I found that my driver side exhaust manifold gasket was leaking right onto my coolant temp sensor, so I went to change that out.. broke an exhaust bolt, pulled the head to get the broken bolt, new head gasket, new intake gasket, and new spark plugs/wires (only driver side thus far), and a new coolant temp sensor.
Still over heating at idle/stop. Thinking my water pump was DOA or not working correctly I used my warranty to swap it out.. same issues.. put another new fan clutch (Extreme duty vs the heavy duty the first time), no change. I put a cleaning agent in (worried my block/heater core were clogged) ran it for about 15 miles, pulled everything apart and hooked a hose up to flush the whole system. (water flows freely through whole system) Same issue of over heating at idle/stop
adding in edit.. I also did a block test to verify my new head gasket (and my passenger side head) were not leaking exhaust gasses into the coolant.. found no issues there
Today I took the front bumper/grill off and found the fan was pushing hot air around by the head lights into the front bumper (IE back in front of the radiator).. I put a small fan in front oscillating (just to prevent hot air buildup in the front) and my temps stayed stable!
Tomorrow I will be building a temporary block of some kind to fill those holes and do a proper test.. but I am hopeful.
I'm surprised that they use a belt-driven fan on a 2008 2500. I would've expected them to use electric fans as they do on the 1500s for this very reason - reducing high temps at idle. That said, putting in new baffles using coroplast was one of the modifications I made to my 2012 XL Denali to keep temps down when towing (in addition to mounting a Derale fan-forced transmission cooler below the bumper and installing a thicker cold case radiator), and I no longer have any problems keeping it cool pulling our 7000 lb camper - either climbing mountains or in traffic. On piston-engined aircraft, engine baffles that seal properly are vital, which is what gave me the idea to replace my baffles on the Yukon.
TBH.. I didn't even know trucks had electric fans in them.. I figured that was a car only type thing due to space. I have 3 trucks (02 Chevy suburban 1500, 08 Yukon XL 2500, and an 04 Chevy Silverado 2500 diesel) and they are all mechanical.. We also have a 2014 Nissan rogue that is electrical fans and an 06 Prius that is electrical fans..
From what I have read in forums when others talk about switching to e-fans (ford taurus fans seem to be super popular) from a mechanical is that the mechanicals are better in low speed high stress environments (towing, extreme up-hill travel).. that being said I couldn't verify one way or the other.. I can only point to what others have said.
I have intentions of going to a bigger/thicker rad, a bigger trans cooler, and possibly an external oil cooler.. My trailer is a 29 ft toyhauler. Current loadout (full water/gear etc is ~8k lbs) and those upgrades are to ease the cooling, but I don't want to do these things now in an attempt to Band-Aid an issue.. The factory engineers spent a ton of time/energy making sure the vehicle could perform; factory spec sheet on my Yukon says I can pull something like 9,500lbs. I want to get back to that point before I start doing other stuff to make sure I am not hiding a bigger issue somewhere.
From what I have read in forums when others talk about switching to e-fans (ford taurus fans seem to be super popular) from a mechanical is that the mechanicals are better in low speed high stress environments (towing, extreme up-hill travel).. that being said I couldn't verify one way or the other.. I can only point to what others have said.
I have intentions of going to a bigger/thicker rad, a bigger trans cooler, and possibly an external oil cooler.. My trailer is a 29 ft toyhauler. Current loadout (full water/gear etc is ~8k lbs) and those upgrades are to ease the cooling, but I don't want to do these things now in an attempt to Band-Aid an issue.. The factory engineers spent a ton of time/energy making sure the vehicle could perform; factory spec sheet on my Yukon says I can pull something like 9,500lbs. I want to get back to that point before I start doing other stuff to make sure I am not hiding a bigger issue somewhere.
I didn't mean to distract from the issue by mentioning the conventional fan - I was just surprised is all. And I agree - the factory design has been engineered to do the job it was rated for, and I also agree that the baffles are a viable culprit in your case.
On the external oil cooler - does yours have cooling lines running from the engine above the oil filter to the driver's side end tank of the radiator? If so then you already have pretty good engine oil cooling and to mount an additional cooler wouldn't likely net you much benefit.
In my opinion though, getting the transmission cooler out from in front of the radiator does provide significant benefits. That single thing made the most difference in BOTH my engine coolant and transmission fluid temps when towing.
No worries
I am learning a ton about vehicles I have owned for years in a very short period of time (I am new to this forum, and have only ever been a part of a diesel forum for my other truck because I am new to them).. its what I love about the GMC/Chevy platform.. usually very straight forward. So side conversations are fine with me I do have the oil cooler built into the rad currently. The only reason I mentioned an external is due to possibly changing out radiators in the future and I have seen a few that are 'blank'.. no oil or trans coolers built in. These are from websites that Juggies and other extreme custom builds get their stuff from and very likely wouldn't work for my application because the oil needs to stay a pretty consistent temp.. but I look at them anyway because they are shiny lol.
I also have the built in transmission cooler... I am torn on weather to bypass the rad altogether with a trans cooler or run it in line.. I found another post on this forum (stupid helpful with temps) that stated 150 is the minimum temp a trans should see during normal operation and 175 degrees provides the longest life (100k miles ish).. where once you hit 200 degrees that life is cut to ~25-40k miles).. towing my trailer I can see 200-225 depending on outside temp + elevation change.. I figure in Az I could bypass the rad altogether.. but when I go up north or out of state where temps get much cooler very quickly.. will that make me 'too cold'? I see the 40k true cool (I think is the brand/model) that is super popular.. and users have noted 30-50 degree drops in temp.. but I don't know their set up (bypass or inline)
On yours.. did you add an e-fan to the trans cooler when you relocated? did you just drop it down into the bumper itself? and did you bypass or keep inline with the rad?
the other post I saw on trans temps is here: Keeping coolant and transmission temps under control when towing in the summer heat | Page 55 | Chevy Tahoe Forum | GMC Yukon Forum | Tahoe Z71 | Cadillac Escalade - Tahoe Yukon Forum
the info from that page:
OIL TEMPERATURES MEASURED IN THE SUMP
150F -- Minimum operating temperature for continuous operation. It is possible in low ambient temperature to overcool the transmission with oil to air-type coolers; it is hard to overcool if used in conjunction with oil to water coolers installed in most standard automotive radiators.
190F-200F -- Maximum oil level checking temperature. Beyond this, readings are not reliable because of expansion.
285F -- Maximum sump/oil pan temperatures for short duration such as a long hill climb.
300F -- Metal parts inside the transmission begin to warp and distort in varying degrees, seals melt rapidly, and transmission fluid life is extremely short due to oxidation and distress.
AUTOMATIC TRANSMISSION FLUID OXIDATION
Automatic transmission fluid can provide up to 100,000 miles of service before oxidation occurs under normal operating temperatures of about 170F. Above normal operating temperatures, the oxidation rate doubles (useful life of the fluid is cut in half) with each 20 degree increase in temperature. The approximate life expectancy at various temperatures is a follows:
Degrees F Miles
175 100,000
195 50,000
212 25,000
235 12,000
255 6,000
275 3,000
295 1,500
315 750
335 325
375 80
390 40
415 Less than 30 minutes
Glad it was helpful. I started that thread while I was trying to sort all of this stuff out, and that information about temps was also a post I recently added from the GM manual. Important to note that the mileage vs temps given is for the *fluid* life, not the transmission life.No worries
I do have the oil cooler built into the rad currently. The only reason I mentioned an external is due to possibly changing out radiators in the future and I have seen a few that are 'blank'.. no oil or trans coolers built in. These are from websites that Juggies and other extreme custom builds get their stuff from and very likely wouldn't work for my application because the oil needs to stay a pretty consistent temp.. but I look at them anyway because they are shiny lol.
I also have the built in transmission cooler... I am torn on weather to bypass the rad altogether with a trans cooler or run it in line.. I found another post on this forum (stupid helpful with temps) that stated 150 is the minimum temp a trans should see during normal operation and 175 degrees provides the longest life (100k miles ish).. where once you hit 200 degrees that life is cut to ~25-40k miles).. towing my trailer I can see 200-225 depending on outside temp + elevation change.. I figure in Az I could bypass the rad altogether.. but when I go up north or out of state where temps get much cooler very quickly.. will that make me 'too cold'? I see the 40k true cool (I think is the brand/model) that is super popular.. and users have noted 30-50 degree drops in temp.. but I don't know their set up (bypass or inline)
On yours.. did you add an e-fan to the trans cooler when you relocated? did you just drop it down into the bumper itself? and did you bypass or keep inline with the rad?
the other post I saw on trans temps is here: Keeping coolant and transmission temps under control when towing in the summer heat | Page 55 | Chevy Tahoe Forum | GMC Yukon Forum | Tahoe Z71 | Cadillac Escalade - Tahoe Yukon Forum
the info from that page:
OIL TEMPERATURES MEASURED IN THE SUMP
150F -- Minimum operating temperature for continuous operation. It is possible in low ambient temperature to overcool the transmission with oil to air-type coolers; it is hard to overcool if used in conjunction with oil to water coolers installed in most standard automotive radiators.
190F-200F -- Maximum oil level checking temperature. Beyond this, readings are not reliable because of expansion.
285F -- Maximum sump/oil pan temperatures for short duration such as a long hill climb.
300F -- Metal parts inside the transmission begin to warp and distort in varying degrees, seals melt rapidly, and transmission fluid life is extremely short due to oxidation and distress.
AUTOMATIC TRANSMISSION FLUID OXIDATION
Automatic transmission fluid can provide up to 100,000 miles of service before oxidation occurs under normal operating temperatures of about 170F. Above normal operating temperatures, the oxidation rate doubles (useful life of the fluid is cut in half) with each 20 degree increase in temperature. The approximate life expectancy at various temperatures is a follows:
Degrees F Miles
175 100,000
195 50,000
212 25,000
235 12,000
255 6,000
275 3,000
295 1,500
315 750
335 325
375 80
390 40
415 Less than 30 minutes
The details of my trans cooler are in that thread as well. It's a Derale 13960 and it has a fan. I also initially set it up bypassing the radiator but that was a mistake. I saw MUCH hotter peak temps when towing than with the radiator plumbed in series before the external cooler. The GM up fitters manual confirms that any external transmission coolers should be plumbed in series with the coolers in the radiator.
donjetman
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Our Denali has the standard duty (KNP) factory external trans cooler that's plumbed in series with the radiator. The one on the viewers left is the trans cooler. I don't tow or sit in stop n go traffic so no overheating problems. If I did tow, I'd add a big cooler with thermostat and fan at the lower grill. A couple of yrs ago I installed a 180* thermostat – Motorad# 523-180. I haven't noticed any difference on the gauge, it has always read 210*.
sorry for such a delayed follow-up to this thread.. I have been incredibly busy.
I pulled the front bumper/grill off. Found the opening(s) where the hot air was circulating back into the bumper/in front of the radiator behind the headlights (also by the front battery tray and intake box).. I put a piece of cardboard that I had wrapped in duct tape in each opening.. put my bumper back on and gosh darn it.. if that wasn't the whole issue.. it was a very large portion. My temps at idle are much more stable (they will still climb some.. but MUUCH slower and it's not consistent, some times they don't climb at all)
With all of that said.. is there a part number for the rubber material to get a factory part/fit again? I don't even know what to call the things.. baffles, air dams? I can't find a part because I don't know what they are called.
The next step(s) is to replace the passenger side exhaust manifold gasket and get a new trans cooler and remote mount it down some out of the way of the rad. After replacing my cardboard cutouts with a more permanent fix
I pulled the front bumper/grill off. Found the opening(s) where the hot air was circulating back into the bumper/in front of the radiator behind the headlights (also by the front battery tray and intake box).. I put a piece of cardboard that I had wrapped in duct tape in each opening.. put my bumper back on and gosh darn it.. if that wasn't the whole issue.. it was a very large portion. My temps at idle are much more stable (they will still climb some.. but MUUCH slower and it's not consistent, some times they don't climb at all)
With all of that said.. is there a part number for the rubber material to get a factory part/fit again? I don't even know what to call the things.. baffles, air dams? I can't find a part because I don't know what they are called.
The next step(s) is to replace the passenger side exhaust manifold gasket and get a new trans cooler and remote mount it down some out of the way of the rad. After replacing my cardboard cutouts with a more permanent fix
