Call for Cooling Experts - Seekling help!
 

Hello Cooling Experts!

I’m seeking you help with a cooling problem I’m having on my Stock 1966 427 390 HP Vette.

I installed my 20 year old, very low mi, recently boiled out & painted radiator in my Vette today.

The engine warmed up as normal, the inside gauge read 200, the radiator inlet was 195*, measured w/ a IR thermometer

I took a short 3 mi test drive at 35 – 40 mi/ hr w/o the hood @ 40 * outside temp.

The inside temp gauge reached 220* when I pulled into the garaged.
The T-Stat housing read 220*
The radiator outlet temp was an extremely cool 95*!!
I put my hand on the radiator & the bottom was only cool to warm & I did NOT have to pull my hand away.

The middle was warm - only after a few seconds I had to pull my hand away.

The cooling fins near the inlet were hot - I could Not hold my hand on the cooling fins.

The top cooling fin opposite the inlet, near the radiator cap was much cooler- I could hold my hand on the cooling fins for a few seconds.

Heck, it seem like the refurbished radiator is clogged?
The car has a new stock water pump, new 180* T Stat, bottom hose has a spring!

I also verified that I properly installed the correct head gasket for this engine.

I called the local radiator shop w/ 40 years exp. He indicated the rad maybe clogged & that he would apply the $65 I paid for the boil out towards a rod out repair.

I removed the rad this weekend & performed the following unscientific flow test.

Positioned the Rad w/ the inlet pointing up & the outlet pointing down, held my hand over the outlet & filled the rad w/ water until it came out the over flow. I removed my hand & measured the height of the water as it came out of the outlet to be 12”. My research indicated that 12” – 14” is normal for a 4 core rad.

I will know more when I have the inlet tank removed and inspect the core at the rad shop.

How can this rad cool so poorly & pass a flow test?

I’m going down fighting w/ this Harrison brass / copper but if I do not find an assignable cause for the above it will be replace it w/ a Aluminum rad.

Where am I going wrong?
Thanks in advance for helping!:cheers:
Andy

My experience with 20 year old copper/brass radiators is that it will need a core installed. Once done, the thing will cool very well.

Sure sounds like the radiator core is plugged.

Hello Mike,

I agree an assignable cause for the poor cooling would be a plugged core but how did it pass the flow test w/ a water exiting height of 12" out of the outlet?

Thanks for your reply!:iagree::cheers:
Andy

Hang in there. Before this is over someone is going to tell you the water is flowing too fast. :D

Forget the flow test. I don't understand what his test was.

What is your "guess" his problem is and then we'll discuss any difference of opinion if there is any.:thumbs:

Possible air lock??? When I do mine every two to three years, I always fill the radiator and let the engine run without the radiator cap until it reaches running tempature and the thermostat opens twice. I also pull the heat control to allow fluid to flow through the heater core. Once that is done I re-fill the radiator and install the cap. Haven't had a problem yet. My car is running the original radiator.

I removed the T-Stat & then added the coolant to the rad & watched the coolant level rise in the intake manifold. I ran the engine w/ the heater on during the initial test drive. The heater worked fine & provided plenty of heat. I thought this would eliminate the potential for an air lock.

The fact that your heater appeared to be circulating coolant further points to no flow thorugh the radiator. I think at this point, you could rule out the water pump and low coolant level.

I would remove the thermostat and do another test. The thermostat could be not opening or just partially open to restrict flow but the heater would still work.

Any chance you might have gotten a rodent nest in the radiator tank before you put it back in?

Have you tested the thermostat in hot water with a thermometer on the stove to see if it is working?. I have been the victim of two brand new thermostats that would not open right out of the box.That will drive you crazy. Always test them!

I checked the T-Stat in a pot of water on the stove to make sure it opened & closed at or near 180*. It is working fine. I also held my hand on the upper rad hose duirng warm-up & it went from cold - hot at 180*.

Mike this rad was boiled out & then installed in the car. Maybe, the boiling out procedure loosened some "gunk" inside the rad & it did not come out when flushed. I installed the rad & now it is plugged.

However, how did it pass the flow test? Water exited the rad while it was on its side, inlet up & outlet down to a measured height of 12”. Yea, it is a crude test but one would think w/ a rad plugged the exit water height would be significant less. Thus, ~ 8” would indicate a plugged rad.

I spoke w/ the rad shop today & plan to have inlet tank removed & visually inspect the core. I will keep you posted on what condition the core is in.


Thanks for helping!
Andy :cheers:

Could be what happened. Radiator shops used to "rod out" the radiator tubes, meaning they were mechanically reamed out and then boiled out/flushed to remove and leftover debris. I don't know if shops ever "rodded" cross flow radiators or not. The last time I saw that done, cross flows were not in use yet.

I would try removing the thermostat and running it one more time to see if the engine gets hot. It might save you a lot of time/effort/money.

PS. I just went back and read your first post. Part of it didn't soak in. I see the shop offered to "rod" the radiator and it looks like your radiator is out of the car now. So, go for it! Either the rod job or a new core, depending on what they find.

Unless you have factory A/C with a functional vacuum-operated water inlet valve, turning the heat on has no effect on coolant flow to the heater core at all on a midyear; without A/C, coolant flows through the heater core all the time - all the heat control does is open an air door inside the heater case. :thumbs:

John,

I should have thought about that. I recently had to replace all the seals in housing, so I should have known that it flows all the time.

Steve

John

What happens differently w/ A/C cars?...what needs to be done when changing coolant in my '66 427/390, w/ factory AC.

Factory A/C cars have a vacuum-operated coolant valve on the firewall where the 5/8" hose from the intake manifold fitting connects to the heater core inlet nipple; when the A/C is on, the valve is closed and no coolant flows through the heater core. If the A/C is off (knob pushed in), the valve is open and coolant flows through the core. :thumbs:

What does Boiled out really mean? I know what rodded out means.

I know of pulling the tanks, running rods through the tubes and putting it back together, then testing for leaks. Top or side flow doesnt matter.

Beware standard procedure is that if the tubes leak they solder them shut and retest, when it stops bubbling it gets painted and delivered.

I also like to dril a few holes in the thermostat to let the bubbles travel to the top and have a small amount of flow when closed.

"What does Boiled out really mean?"

The rad is placed in a tank of hot chemicals designed to clean the inside & outside of the rad.
After a few hours of tank time the rad “should” come out clean inside & out and hopefully w/ all the tubes in the core wide open.
The rad is then pressured washed inside & out; tested for leaks, “flow tested”, painted & returned to service.

This, hot tank cleaning did not help my rad at all.
Thus, now the request for the rod out procedure.

Heck, I want to know why my rad:
1. cooled so poorly
2. exhibited all the signs of a plugged rad
3. pass a flow test

The repair is only as good as equipment used by the rad shop & the skill level of the rad repair guy. Heck, my rad guy has been in business for 40 years but now his grandson is doing most of the work.

I will post the results of core condition when the inlet tank is removed.

Andy

So the radiator isn't hot enough that you can't touch it and the engine is. How would that tell you the the radiator isn't cooling enough? Wouldn't it be hot too?