I am having trouble with overheating and boiling at idle on my stock 72 W30. It runs cool at speed, just having issues in park. When I bought the car it had a direct drive setup with no fan clutch so it was on all the time. It cooled okay but I wanted to change it back to a factory correct system.

I bought the KJ, KN and KG pulleys from Fusick along with a Hayden 2747 clutch and a 7 blade fan. As I said, it cools fine at speed but will boil over when stopped in park. Questions:

1. My mechanic says there is a small "wobble" in the I think the carnkshaft or water pump pulley but he didn't think it was a big issue - is it?
2. How far back should the fan be in the shroud? Is it adjustable?
3. This is the radiator in the car, less than a year old -
https://usradiator.com/product/oldsm...4-row-radiator
4. Could the water pump be bad (hence the wobble)? Could it be the wrong depth?

I am looking for any and all help, I really don't want to have to look at aluminum radiators, electric fans, etc. it cooled fine when new! Thanks.

 

The fan should be 1/2 in and 1/2 out of the shroud.

 

By no means an exhaustive list of possible thoughts but some, pending others who may weigh in further

Are your hoses and T-stat known good condition - bottom hose have coil in it?

What kind of water pump are you running and how old?

Is the pulley combo you're running known correct for your motor?

When last changing your rad cap and what pressure is it?

Aluminum rad is a great upgrade and there are reasonable cost options if you don't want to go all in for something like Cold Case or Be Cool brands.

https://www.autocityclassic.com/chev...tor-sl-282-at/

Is your coolant running clean?

I run a Be Cool rad with a 7-blade GM fan ('76 corvette) and 160 T-stat, Milodon water pump, Carquest 215046 fan clutch and stock shroud. My engine temps almost never exceed 180 unless at extended idle on a hot day, when it may creep up to 190-200 at most.

I have a factory a/c car (now Vintage Air), so that's with a condenser installed and I also run a trans cooler for my TH350. Maybe your rad has a flow problem?

 

Adding to the list of items to check:
Check the radiator preferably with an IR thermometer for cold spots indicating a blockage,
Check the freeze protection to confirm no more than 50% coolant.
Is the cooling system clean? If not CRC ThermoCure is excellent.

Are the flaps around the exterior of the radiator all intact? They prevent air being pulled around the radiator and draw it through the radiator. Cool running at speed indicates a good radiator and points toward insufficient airflow through the radiator at idle.

What is the temperature difference between the upper and lower hoses?

 

Why did you change the pulleys you had?

Please clarify what you changed, and ONLY what you changed, to make it boil over. Was the radiator changed earlier?

When you bought the car, it cooled ok, so all that was there then was fine. Did your mechanic forget the shim on the clutch? That may be the wobble. I did that last year.

The only thing you changed was fan and clutch. Did you put the fan on the right direction? Does the clutch work? The way to confirm the clutch works is 2 tests, and 4 results. If it spins freely at any time, by which I mean several revolutions, it is shot. Spin it by hand with engine off and cold. It should spin half a turn or so. Spin it by hand with engine off and hot. It should move about a blade width only. It it ever free spins, or completely locked up, it is shot.

 

^^x2^^

Sometimes it's the simplest of things. The spring weak, seal(s) deteriorated, vacuum valve stuck? $10 for a new 16psi cap.

 

If it does not overheat at speed but does at idle you either have an airflow problem or a bad radiator. At least that is the most likely.

 

Thanks everyone, I'm passing all this information on to my mechanic. I know for sure that the fan is not where it should be. I'll keep you all posted.