Coolant Pressure 6.0L Vortec

[millerladam]

I have a 2007 Yukon XL 2500 SLT with the 6.0L Vortec engine. It has approximately 86k on it. It was purchased shortly after this passed Thanksgiving when I blew my Duramax up (that's another story for another time) and was purchased specifically so I can tow my 30' toy hauler while my Duramax is being rebuilt. The maintenance records according to CarFax was spotless, meaning, the vehicle has been meticulously taken care of since purchased new and that I am the second owner. The vehicle was purchased here in AZ and was serviced at the same dealership it was purchased at until I purchased it from Lifted Trucks. I have changed the air filter once, engine oil twice, spark plugs and plug wires. Most recently, I flushed the entire cooling system and changed the thermostat when the truck start running over normal operating temperature while sitting at idle in 100+ degree weather.

Yesterday, we drove the vehicle approximately 30 miles to my in laws. I had no issues on the way to their house until I stopped at the bank to pull out some cash to help pay for dinner. While sitting at the drive up ATM for no more than 5 minutes, the truck reach approximately 225*, which is 15* over my normal operating temperature. I have read that GM deems this as being "normal" however, I refuse to accept that. I have also read that the GMC Sierra's and Chevy Silverado's 2500's with this same body style and engine have a larger radiator and an electric fan in front of the radiator as well as the mechanical fan driven by the crank. Does anyone know if this is true? If so, why the hell did GM not use the same radiator on this Yukon with the same engine? Also, the cooling system doesn't seem to hold pressure. For example, I can easily squeeze the upper radiator hose while the truck is running and at full temperature. Is this cooling system supposed to hold pressure? I changed the reservoir cap but it didn't make a difference. Does anyone have any information about putting the larger radiator into my Yukon from a Sierra/Silverado 2500 from the same year/chassis?

Thank you!

 

[millerladam]

Bump... All of the members on this forum that drive a Yukon / Tahoe that have a 6.0L and no ones knows if these systems are supposed to hold pressure?

Items Checked / Replaced

1. Flushed entire Cooling System with hose
   
2. Replaced Thermostat with AC Delco OEM
3. Replaced coolant with AC Delco DexCool
   
4. Checked Fan Clutch
5. Cleaned Radiator with Pressure Washer
6. Cleaned Fan with Pressure Washer

Any help is appreciated here. Thank you!

 

[TheAutumnWind]

All coolant systems should hold pressure.

Rent a coolant pressure tester from your local autoparts store.

 

[2007tahoe]

Didn't realize the 6.0 still had a fan clutch is 2007. My 2007 5.3 only has a electric fan. How did u check the clutch? I would just replace the fan clutch anyway. That is going to affect your temp at idle. I replaced the fan clutch on my brothers truck with an oem for the dealer a few years back and it only lasted about 3 years before it went out again. Also I would check the system for leaks like stated above.

 

[millerladam]

All coolant systems should hold pressure.

Rent a coolant pressure tester from your local autoparts store.

That being said, how much pressure should this system hold? For example, before I do the pressure test, if the truck were running and up to operating temperature and I were to squeeze the upper radiator hose, how far should I be able to pinch the sides together, if at all? I know on my Duramax it wasn't rock solid but it was definitely holding pressure. This one doesn't seem to hold much pressure if at all.

 

[millerladam]

Didn't realize the 6.0 still had a fan clutch is 2007. My 2007 5.3 only has a electric fan. How did u check the clutch? I would just replace the fan clutch anyway. That is going to affect your temp at idle. I replaced the fan clutch on my brothers truck with an oem for the dealer a few years back and it only lasted about 3 years before it went out again. Also I would check the system for leaks like stated above.

Mine is definitely a fan clutch. We basically got the truck up to operating temperature then shut it off and tested to see if the fan had any resistance which should indicate that the clutch is / was engaged. You can also hear it kick it up and power loss. I swear I had better not have blown head gaskets on this damn truck but I don't notice any coolant loss so I don't think that is the problem. I think it might be a problem with one of the radiator hoses because it doesn't seem to hold pressure. It could also be the reservoir but again, I have no coolant loss from what I can tell.

 

[millerladam]

Bump... Anymore input?

 

[TheAutumnWind]

That being said, how much pressure should this system hold? For example, before I do the pressure test, if the truck were running and up to operating temperature and I were to squeeze the upper radiator hose, how far should I be able to pinch the sides together, if at all? I know on my Duramax it wasn't rock solid but it was definitely holding pressure. This one doesn't seem to hold much pressure if at all.

All coolant systems should hold at least around 12psi. Not sure why you aren't getting many comments. Maybe because this is such a simple question easily answered with a Google search.

I recently had to replace a water pump. Didn't have noticeable coolant loss or higher temps for quite awhile but was noticing a bit of coolant under the waterpump, and could smell it occasionally.

 

[adventurenali92]

I recently also had to replace my water pump and I had the same thing. No coolant loss in the system. Nor did my truck run any higher temps than normal.

 

[millerladam]

I am resurrecting this thread to provide an update.

My problem still isn't fixed. The truck will begin to get warm (higher than normal operating temperature of 210*) while sitting at idle. What I have noticed is that this happens when the outside temperature is more than 100* and the transmission temperature is over 180*. I took the truck to a local dealership yesterday and had them flush the transmission. I am going to call them tomorrow because when their oil lube technician did the oil changed and checked the air filter, they removed the intake tube for some reason and lost one of the damn clamps. I also want to know if their "transmission flush" involves dropping the pan and changing the filter.

Since the transmission flush didn't help, I went ahead and changed the fan clutch today. Two weeks ago, I went ahead and replaced the upper and lower radiator hoses, surge tank and surge tank cap. The system NOW builds and holds pressure, it was not prior. However, it still gets over normal operating temperature when sitting at idle for more than 5 minutes.

So, here is the full list of what I have done.

1. Upper and Lower Radiator Hoses (AC Delco OEM)
   
2. Thermostat (AC Delco OEM)
3. Coolant Surge Tank (AC Delco OEM)
4. Coolant Surge Tank Cap (AC Delco OEM)
5. Fan Clutch (Murray)
6. Flushed Cooling System (twice) and used AC Delco Dexcool

I have access to an AC Delco parts distributor so I try to use OEM parts when I can. The only reason the fan clutch is a Murray is because my distributor isn't open on Sunday's and I wanted to do it today.

I am at a complete loss! I towed my brothers little trailer (single axles, enclosed, less than 2000lb) about 30 miles to my sisters house today and the engine got to around 225* and the transmission got to about 205*, with that little trailer and the outside temperature around 105*. I am planning on attempting to pull my 8000lb toy hauler up north this coming weekend but I am afraid the truck is going to actually overheat and leave my family and I stranded. If anyone has ANY suggestions, I am all ears. I am sick of throwing money at it but don't have the $130/hr for the dealer to diagnose the issue. I am very mechanically inclined (rebuilding my Duramax LLY right now) and I have always worked on my own vehicles.

The only items I have yet to replace in the cooling system are the water pump and the radiator. The truck has less than 90k miles on it! Please, any suggestions are appreciated!

Thank you!