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Chevrolet Express
Platform: GMT Van

Help! Van driving me crazy

Old Aug 27, 2019 | 4:19 PM
  #11  
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Maybe the previous owner watered down the coolant and the pump was starved of lubrication.
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Old Aug 27, 2019 | 4:26 PM
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Originally Posted by ExpressvanMan2000
And yeah im not looking forward to probing around with the stethoscope due to how close the fan blade is the accessories on these vans.
The good news is that the back side of the fan doesn't "grab" like the front does. I bumped the stethoscope rod against the fan blades a couple times while probing. It'll scare the $h** out of you (especially if the stethoscope is in your ears), but if you're being cautious you should be fine. You are right though, there's some tight spaces between moving parts, so probe carefully.
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Old Aug 27, 2019 | 4:29 PM
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Originally Posted by mountainmanjoe
Maybe the previous owner watered down the coolant and the pump was starved of lubrication.
I hadn't considered that, but I didn't have any problems with coolant boiling off. So if it was watered down, it wasn't much (or the damage was done before I owned it).
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Old Aug 27, 2019 | 4:33 PM
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Antifreeze changes the freezing point of water by a lot, but it only changes the boiling point by 6 degrees or so at sea level. Since the cooling system is pressurized, water should not boil off.
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Old Aug 27, 2019 | 9:13 PM
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So i took off the serpentine belt and now i dont hear the squeal. Also tried moving the water pump pulley and the one right below it that turns all the other pulleys. No movement in either one..about to do a load test.
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Old Aug 27, 2019 | 9:52 PM
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Originally Posted by mountainmanjoe
Antifreeze changes the freezing point of water by a lot, but it only changes the boiling point by 6 degrees or so at sea level. Since the cooling system is pressurized, water should not boil off.

I had to look it up for my own edification. I knew the coolant played a significant role on the freezing side, but I didn't realize that it plays such a lesser role in the boiling point (at least for a 50/50 concentration). So, maybe they ran it lean? Who knows?

ExpressvanMan2000, I hope your load test reveals some answers.

Last edited by GatorHawk24; Aug 27, 2019 at 9:53 PM. Reason: typo
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Old Aug 27, 2019 | 10:50 PM
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Originally Posted by GatorHawk24
I had to look it up for my own edification. I knew the coolant played a significant role on the freezing side, but I didn't realize that it plays such a lesser role in the boiling point (at least for a 50/50 concentration). So, maybe they ran it lean? Who knows?

ExpressvanMan2000, I hope your load test reveals some answers.
thanks...well did the test and what not. Took the belt off and sprayed some wd40 around where the bearings would be on the water pump and cleaned some more of the soap crud off the pulleys...i only hear the noise now upon reving the engine.. wont no much more til i get the stethoscope. But my money is on the water pump bearings or left over soap crud but doubt its the soap since the noise was there before i soaped up.

Edit:i do hear a slight grinding or tapping noise upon lightly reving the engine and it sounds like its coming from the lpwer front of the engine.

Last edited by ExpressvanMan2000; Aug 27, 2019 at 11:01 PM.
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Old Aug 28, 2019 | 12:17 AM
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Originally Posted by GatorHawk24
I didn't realize that it plays such a lesser role in the boiling point
It's a very widespread misconception, but it's all in the name: antiFREEZE. Water actually has far more capacity to carry away heat than antifreeze does. That's why it's there. If you ran your engine on pure antifreeze (ethylene/propylene glycol) then it would overheat quite quickly. It's there to: prevent freezing, corrosion and to lubricate. NOT boil-over protection. The rad cap does that. Modern systems run even hotter (plastic radiators etc.), and require higher pressures so sealing is even more important.


In any case, belts squeel when they slip. If the belt is new, then one of the pulleys is seizing up, or the grooves are worn out and the belt is slipping through. Or it's misaligned.
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Old Sep 4, 2019 | 7:49 PM
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Originally Posted by GatorHawk24
ExpressvanMan2000,

Short story... Check the water pump with an automotive stethoscope and someone in the driver's seat who can responsibly adjust engine RPM at your command.

Long story... I had a similar-ish issue with my 2016. It developed a noise that I knew was belt related, but not the belt itself (it sounded more mechanical, like a bearing). I replaced the serpentine belt, the tensioner, and the idler pulley, since they were relatively inexpensive, I could replace them in my driveway in under an hour, that was the general area the noise seemed to be coming from. That didn't fix the issue. I went to a local Harbor Freight and picked up an automotive stethoscope and started probing around... word of caution, be extremely careful/cautious when probing a running engine, there's a lot of fast moving parts! I thought it might be the alternator, but when my son revved the engine, the pitch changed but not the intensity of the sound. The water pump was the very last thing I checked (of course, right?), and it was the source of my noise. Thankfully, my van was still within its power train warranty, so that was a blessing.
wasnt the water pump...van still squealing.

What do i do know. Other then take it top a shop which is my next step if know available help from here arrives..
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Old Sep 4, 2019 | 7:49 PM
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At idle I only hear it upon giving it gas
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