Disaster - Overheating

[JimInRadfordVA]

Was leaving my son’s wedding rehearsal. No warning, no nothing, temperature gauge pegs high. By the time I got it off the road, the pointer swung back the other way to zero. Popped the hood, stream everywhere. A cursory inspection (I cursed while looking at the engine) didn’t show a thrown belt or blown hose.

I’ll have to go back in the morning to look more closely. I’m praying it’s not a head gasket.

 

[Mooseman]

Could be as simple as a stuck closed thermostat.

 

[JimInRadfordVA]

What’s the best way to diagnose that? Refill with dexcool and see what happens?

 

[Mounce]

Take a flash light and find the leak. Check radiator and hoses, water pump, heater hoses.

If everything is soaked and you can't tell where it's originating from then I'd consider filling and watching to see if I could find the leak.

From your description it sounds like a major failure of a hose, have been there multiple times in a different vehicle.

 

[Locksmith]

If you wait till engine is cold, fill radiator with water, start the engine with radiator cap off, the when engine warms up, rev it, and if you see a geyser, your thermostat is stuck closed. Old timey advice! Keep us updated!

 

[JimInRadfordVA]

My son is getting married today, so it’ll have to wait a day, unless I can work on it between the ceremony and the reception. Think my wife will mind?

I’ll take a few gallons of water and see what’s what. Right now I’m thinking a little more clearly. When I wás getting off the road and watching the gauges I saw that the voltage gauge was down to around 10 volts. Either the serpentine belt was slipping or the water pump locked up.

Worst case scenario: It’s a blown head gasket and I get to shop for another Trailblazer.

 

[JimInRadfordVA]

Finally managed to get back to the TB yesterday afternoon. Poured 2 gallons of water into the radiator. I immediately observed a massive leak at the water pump. Engine starts and runs OK. No coolant in the oil. I'm arranging to have it towed and repaired today.

One question on the fan--should it be fully engaged and "roaring" at start-up? With a cold, non-running engine the fan will turn, but with a good amount of resistance. Should it freewheel?

 

[Locksmith]

I highly recommend changing the fan clutch with an original AC Delco unit with the new pump. I bought a new fan clutch and it was an after market and didn't work right. I sent it back and got a thermal clutch (mechanical) rather than the electro-viscous clutch (computerized) and had PCM of NC reprogram my PCM so it would not show a code.

 

[JimInRadfordVA]

Does anyone have the part # for the correct thermal clutch?

 

[Locksmith]

I believe after 2008 GM went back to the thermal clutch, but search GMTNation for the answer.

 

[Sparky]

Sometimes having a full lock on roar at cold start is normal due if the clutch comes to rest at a position that the stuff inside pools in the full on. But it should return to normal fan speed fairly quickly. But, if you're taking it all apart to do the water pump, it might be worth upgrading to the thermal only one while you're in there, if budget allows. As noted, you'd have to get a PCM tune to ditch the fan code. Another tuning option is @limequat http://www.lime-swap.com/ as he's cheaper and can do the same kind of thing. Get a few tune goodies while you're at it.

I believe AC Delco 1540144 is the thermal clutch. Alternatively, the Hayden 2851 is good too I believe.

 

[JimInRadfordVA]

Thanks, Sparky. I looked up the thermal clutch for a 2008 on Rock Auto and came up with ACDELCO 1540144 as well. Since I'm having my local shop do the work, I'll tell them to use that part.

Alternately, how much of a pain-in-the-ass is replacing it myself? I'd rather get the truck back ASAP and do the clutch later.

 

[Sparky]

Water pumps aren't that bad a job. The hardest part is just getting the fan/clutch out of the way. I think the water pump can be done without fully removing the fan and shroud, though space is limited. The shroud is annoying to remove though. And threading the clutch back on is fun because it is a fine thread, and lining it all up can take a few tries (well at least it did for me).

 

[JimInRadfordVA]

The vehicle is stuck on a back road parking lot, and I'm not in a position to do the water pump there. Once it's towed and the water pump is fixed, I can replace the fan clutch at my house, on my time.

 

[Matt]

You can do the water pump and fan clutch in 60 minutes or less...if it takes any longer you shouldn't be doing it.

Here's my How to...https://gmtnation.com/forums/threads/how-to-replace-the-water-pump.15639/

 

[JimInRadfordVA]

You can do the water pump and fan clutch in 60 minutes or less...if it takes any longer you shouldn't be doing it.

Here's my How to...https://gmtnation.com/forums/threads/how-to-replace-the-water-pump.15639/

I'm in a wheelchair and need the stuff I have at home in order to get to the engine compartment. I do appreciate the link, though.

 

[Matt]

I didn't realise Jim...if the shop tries to take more time than that...show THEM the how to so they can see how easy it is.

 

[JimInRadfordVA]

I've used these guys for years and they always treat me right.

 

[Locksmith]

Water pumps aren't that bad a job. The hardest part is just getting the fan/clutch out of the way. I think the water pump can be done without fully removing the fan and shroud, though space is limited. The shroud is annoying to remove though. And threading the clutch back on is fun because it is a fine thread, and lining it all up can take a few tries (well at least it did for me).

I made a small square cut near the upper radiator neck so the shroud would be able to clear and lift, courtesy of a guy on YouTube! I used a short chain link bolted to one of the four water pump bolts and the other end of the chain had a long screwdriver stuck through it to a metal bracket top right side (alternator?) to keep the fan nut from spinning It loosened it. Don't forget to pry the trans cooler lines from the shroud clip.

 

[Mooseman]

Your '08 already has the thermal clutch, which is way more reliable than the previous electro-viscous clutch. It is normal for it to roar a bit sometimes on startup and quiet down after a little while. Unless it's a very high mileage unit, I'd try leaving it.

If you do wind up replacing it, go with a Hayden. It's our go-to for these and usually way cheaper than ACDelco.

 

[JimInRadfordVA]

Your '08 already has the thermal clutch, which is way more reliable than the previous electro-viscous clutch. It is normal for it to roar a bit sometimes on startup and quiet down after a little while. Unless it's a very high mileage unit, I'd try leaving it.

If you do wind up replacing it, go with a Hayden. It's our go-to for these and usually way cheaper than ACDelco.

I have an '05. I looked up the '08 part to find the thermal clutch part number. Thanks for the Hayden tip.

 

[Mooseman]

Your profile says 2008 which is what I went with. In that case, if you want to switch to the less trouble prone thermal clutch from '08, then you would need to get your PCM tuned to kill the codes for it and keep your CEL off. You can test the E-V clutch as per this
How to test the electro-viscous fan clutch

 

[JimInRadfordVA]

Your profile says 2008 which is what I went with. In that case, if you want to switch to the less trouble prone thermal clutch from '08, then you would need to get your PCM tuned to kill the codes for it and keep your CEL off. You can test the E-V clutch as per this
How to test the electro-viscous fan clutch

Thanks for the heads-up and the link. I've corrected my profile.

 

[JimInRadfordVA]

Picked up the TB this afternoon. Spoke to the mechanic. After he did the water pump, he pressure tested the system. No leaks evident both internal and external. I had just scored an overstock Goodyear serpentine belt from Rock Auto for cheap, so he used that on reassembly. Purrs like a kitten and holds a steady temp while idling with the a/c on.

Next up: check the fan clutch, and hit up Limeswap for a tune.

Life is good.

 

[Blackstar]

Fan clutch might be ok. Mine was acting up a couple months ago. 4 or 5 codes set, reduced engine power, fan locking up. Checked everything I could, then found she was low about 1/2 gallon of coolant. Topped up and ran up to temp and let all the air out of system and everything went back to normal... even the fan clutch.
What I'm saying is it might have been where you over heated and was obviously low on coolant.

Good luck.

 

[JimInRadfordVA]

I believe that this is exactly what I was experiencing. Fan clutch seems to be working as designed. I’m not going to mess with it. On to scheduling a PCM tune!