[Sootfoot33]

-20C in Ontario today and I really wanted to see if the 6.5 would start. Sure enough she did and it wasn’t that bad. I drive to work, not a problem. Get off work, now getting it started after work -36c with wind chill, was hard. But she fired up and I let it idle for a few mins then started the drive home. No heat from the heater, even though it was up to temp. A few mins later temp starts climbing to 100C, then past! I pulled over quick and turned the motor off. I started it back up 10-15 mins later and limped it to a gas station, waited another 20 mins then got it home without it over heating again. Expansion tank was full to the brim, I pulled the rad cap once it cooled down and it was half empty, and low coolant light was flashing on the last leg of the way home. Not sure what’s going on but I hope I didn’t crack the head. It got to at least 110c maybe 112c and I know 6.5’s don’t like anything past 100c.

 

[Tommygunner]

You should make certain to test that your cooling system is protected to -50 or below. Your radiator may have frozen or slushed up and caused the overheating issue and coolant to be forced out of the system.
Getting it up to 110c is hot, I hope no further damage was done. Take the cap off the overflow tank. Start the engine warm up to operating temp Check for bubbles in the overflow tank. If continuous bubbles then you may have a blown head gasket or crack. No bubbles you should be ok. Another check is. On a cold start with cap on coolant tank feel the top radiator hose. If it gets hard to squeeze together right after starting, then there are gasket /crack problems

 

[Sootfoot33]

You should make certain to test that your cooling system is protected to -50 or below. Your radiator may have frozen or slushed up and caused the overheating issue and coolant to be forced out of the system.
Getting it up to 110c is hot, I hope no further damage was done. Take the cap off the overflow tank. Start the engine warm up to operating temp Check for bubbles in the overflow tank. If continuous bubbles then you may have a blown head gasket or crack. No bubbles you should be ok. Another check is. On a cold start with cap on coolant tank feel the top radiator hose. If it gets hard to squeeze together right after starting, then there are gasket /crack problems

sounds good I’ll try this.Your probably right as I have mixed it 50:50 but have topped up with distilled water, I do have bubbles immediately after turning the truck off. I don’t think there is any while truck is running. I’ll test top rad hose for stiffness today & report back.

 

[Sootfoot33]

Ok I have a bit of an update. Today I started up the 6.5 only -4c out. Fired right up, a few bubbles in the coolant but the top rad hose did not get stiff even after 5 mins of idling still soft no pressure in it at all. When I squeeze & massage the rad hose I do get some burping in the expansion tank. The rad looked a little low on fluid so I topped it up. The expansion tank has a lot of fluid. When I came outside yesterday the fluid was very thick like slush so obviously I don’t have my mixture right. I’ll be getting a test kit shortly to verify what’s going on. Hopefully there’s no damage to the head or block. I know there motors are notorious for cracks etc.

long term radar shows mild days for the next little while so I don’t think it will be freezing up again anytime soon, but I’ll be sure to get the proper mix in there asap

 

[Sootfoot33]

Another update. I am getting contact bubbling in the reservoir, no top rad hose stiffness though. The truck seems to be running great, ill watch for coolant loss. So far no coolant in oil or oil in coolant, no white smoke….. im assuming the head is cracked or gasket is blown but the only symptom so far is bubbling….. maybe air is getting in some how. How else can I diagnose this? Should I just keep driving & not worry about it?

 

[OkDually]

Another update. I am getting contact bubbling in the reservoir, no top rad hose stiffness though. The truck seems to be running great, ill watch for coolant loss. So far no coolant in oil or oil in coolant, no white smoke….. im assuming the head is cracked or gasket is blown but the only symptom so far is bubbling….. maybe air is getting in some how. How else can I diagnose this? Should I just keep driving & not worry about it?

A coolant gas tester kit could tell you if in fact that the bubbles are combustion gasses.

 

[Tommygunner]

You could also do a compression test.

 

[dieselolds]

You can also remove the belt and coolant cross over and start the engine and watch for excess bubbles from each cylinder head.Both sides may show bubbles but if it’s only one side at least you can concentrate on that side a little more closely although both sides will still need to be checked and gone through.

 

[caldiesel]

I'd opt for the coolant gas test 'cause I'm lazy and already have the tester.

 

[Sootfoot33]

Hey guys I have an update. The truck seemed to be working better but still having bubbles in coolant. I worked the truck hard the other day, had to pull 4000 kg’s of weight approx 100 miles. The 6.5 worked fantastic on the HW, wasn’t overheating, wasn’t loosing much speed up long hills. Had to make a stop in town before heading home. Turned the truck off, few mins started up and headed home and temps started to rise, 100 Celsius , I pulled over turned the truck off. Coolant gushing out from expansion tank. I waited for some time, took the rad cap off and topped up the rad and continued home. I watched the temps climb then t stat opened and thought I was good. Then 5 mins later temp climbed again to 100 Celsius, I pulled over and by the time I pulled over t stat opened again and temps dropped. Made it home the last 15 mins with no issues.

it seems like either the rad fan isn’t doing it’s job good enough or the t stat is taking too long to open, causing temps to climb or both

 

[Twisted Steel Performance]

Most likely both....

 

[KenAsh]

I would definitely r&R the T-State. If your temps are rising at low speeds, then, I'd suspect the fan, as it's the low speeds that it comes into play. Maybe, while at it, use an IR gun to test RAD temps at top and bottom just for reference.

 

[Sootfoot33]

Update! I replaced the thermostat with a genuine gm ac delco 190 degree unit but now the truck is not getting up to temp. It will not warm up past 140f for some reason. I went for 50 mile round trip half was hw doing 60 mph other half was hilly back roads and it will not get up to temp. Faulty thermostat? Faulty temp sensor? Heat is not blowing as hot either so I think the gauge is reading somewhat accurately.

 

[OkDually]

Update! I replaced the thermostat with a genuine gm ac delco 190 degree unit but now the truck is not getting up to temp. It will not warm up past 140f for some reason. I went for 50 mile round trip half was hw doing 60 mph other half was hilly back roads and it will not get up to temp. Faulty thermostat? Faulty temp sensor? Heat is not blowing as hot either so I think the gauge is reading somewhat accurately.

I would test the thermostat

 

[Sootfoot33]

I would test the thermostat

Just tested the stat, started opening at 190 ish like it should

 

[OkDually]

Just tested the stat, started opening at 190 ish like it should

Check and verify the temps with a scanner that can read live data, also use an Infrared temp gun and take readings on the upper and lower rad,
Upper rad hose, and the thermostat housing to see if they are close to what the scanner reads

 

[Sootfoot33]

Check and verify the temps with a scanner that can read live data, also use an Infrared temp gun and take readings on the upper and lower rad,
Upper rad hose, and the thermostat housing to see if they are close to what the scanner reads

l

10/4 I’ll report back. Does anyone have the part number for the temp sensor for the gauge? Best I can tell it’s the 213-77 or 25037332. But I can’t tell if that’s the sensor on the head or the sensor on the rad. Thanks

 

[OkDually]

l

10/4 I’ll report back. Does anyone have the part number for the temp sensor for the gauge? Best I can tell it’s the 213-77 or 25037332. But I can’t tell if that’s the sensor on the head or the sensor on the rad. Thanks

the 7332, 213-77 numbers is for the sensor to the gauge.
The PCM sensor is:

• GM (sensor for PCM): 15326386
• AC Delco (sensor for PCM): 213-928

found in the 6.5L FAQ ( parts list section)

 

[skylark]

You mentioned that your heat didn't feel warm. If you had good heat right before this happened and you've tested the thermostat then the only answer is an air bubble.

Either jack the front end up or park on a hill and loosen the thermostat housing and remove the coolant temperature sensor. Slowly fill with coolant until it starts coming out of the housing and tighten it up. Continue filling until coolant reaches the CTS and reinstall it.

If that doesn't work, the only other option for air removal would be to flush the heater core by removing both hoses at the engine and flushing/filling the heater core and hooking the lines back up. This usually isn't necessary.

 

[Sootfoot33]

You mentioned that your heat didn't feel warm. If you had good heat right before this happened and you've tested the thermostat then the only answer is an air bubble.

Either jack the front end up or park on a hill and loosen the thermostat housing and remove the coolant temperature sensor. Slowly fill with coolant until it starts coming out of the housing and tighten it up. Continue filling until coolant reaches the CTS and reinstall it.

If that doesn't work, the only other option for air removal would be to flush the heater core by removing both hoses at the engine and flushing/filling the heater core and hooking the lines back up. This usually isn't necessary.

ok I’ll try this. I was not able to salvage the new stat gasket I just put on so ill need to pick up another tomorrow. & heat coming out was warm but not hot like usual