Getting hot at idle - what next?

[dyeager535]

When you went from V-belt to serpentine, you swapped to the reverse-rotation water pump, right? I don't know why, but sometimes water pumps are just bad these days. Also possible to get one mislabeled or in the wrong box, too.

How much is the fan turning at idle? Right after you shut it off hot, how hard is the fan to spin?

I assumed the OP is talking about the "semi-serpentine" (my trademark lol) setup that really isn't serpentine at all. Just a serpentine style belt (flat, ribbed) that doesn't use idlers or tensioners. Maybe GM did use a combination true serpentine/v-belt setup but I'm unaware of one.

If I remember others experiences correctly, using the wrong rotation water pump often the vehicle idles at the proper temp, but any throttle and the temp climbs rapidly.

I don't see this as a coolant flow issue or the problem would be worse under load (cruise, higher RPMs) and less at idle/no load, which it's not.

Upper and lower hoses are soft with the engine off, solid with the engine running?

 

[AZ79K5Project]

forgot to ask, it get hot with and w/o the a/c on ?

Got some time today to do some checks.

There was no difference between AC and no AC. I’ve bumped up the fan from the stock 19.5 to a 20” fan. The shroud is tight. It helped a little. The temp gain slowed with that.

looks like a nice cooler do have a trans temp gauge ?

I have a trans temp from the side of the transmission. I think it’s the high pressure port or something like it. Drivers side of the 700R4.

The trans temp is low unless I’m pushing it. Normal driving in the heat - it hits around 160. It’s about 4-6” in front of the condenser (in front of the center support).

The 17” radiator has me thinking too.

The semi serpentine is a standard rotation. V-belt on the AC and PS. 5 rib to the Alt.

I don’t want to just throw parts at it. I was looking at this radiator:

Radiator 1985 Chevrolet C20 Suburban - 5.7 Liter V8 350Cid Radiator Aluminum 3 Row, 28 X 19 Core For 2 3/8 Headers | Radiator Express

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[AZ79K5Project]

I assumed the OP is talking about the "semi-serpentine" (my trademark lol) setup that really isn't serpentine at all. Just a serpentine style belt (flat, ribbed) that doesn't use idlers or tensioners. Maybe GM did use a combination true serpentine/v-belt setup but I'm unaware of one.

If I remember others experiences correctly, using the wrong rotation water pump often the vehicle idles at the proper temp, but any throttle and the temp climbs rapidly.

I don't see this as a coolant flow issue or the problem would be worse under load (cruise, higher RPMs) and less at idle/no load, which it's not.

Upper and lower hoses are soft with the engine off, solid with the engine running?

Yes - everything looks good and the system holds pressure.

 

[Wes Harden]

I would check for exhaust gases in radiator. You seem to have covered every thing else. might be a small crack leaking compression into cooling slowly.

 

[AZ79K5Project]

I spoke with the techs at Radiator Express. I was really impressed with them. They said the Cold Case radiator is sufficient they pushed me away from the one I was looking at. I’d highly recommend them for any future purchase.

I called Cold Case as well. Equally good information. Great tech too. Both companies were great to work with.

So, I discovered something by complete accident today. Everything I read, (once I found a random link) says that at least 1/3 to 1/2 of the fan blade should be outside of the shroud because of air turbulence. Checked a couple of stock vehicles and they were following that guideline.

Time to adjust the shroud.

 

[76zimmer]

Yes, blades should be 1/2 in/out of the edge of shroud. Its amazing how effective the shroud can be when all the edges are sealed up to only allow flow through the radiators.