Cooling issues

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cazsper

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Location
Sunnyvale, CA
My Car
1968 Coupe: 393w, TKO-600, Maier Racing springs, Global West suspension, Currie 9in with forged axles, 3.50 gears, Trutrac, Baer brakes front/rear
1973 Mach-1: 351c 4V, C-6, 3.73:1 gears and a long "To Do" list..
I have some cooling issues on my '73 Mach-1 and I'm hoping someone can help me out. First of all, my car has a 4v Cleveland. It has a rough idle flat tappet (hydraulic) cam. It has dual points, Air Gap intake, and a 650cfm carb. The trans is a c-6 with 3.50 gears. The radiator is aluminum (looks pretty clean inside) it has a custom made aluminum fan shroud and 2x electric fans (single speed) that come on as soon as the key is on.

I have replaced the thermostat already. When I removed the t-stat, I did feel that "disk" that sits right below the t-stat.

This is a lot of info- but just in case it helps.. As soon as it warms up, it seems to stay at about 180-185' for about 5-6 miles on the freeway on an 80' day. After that, it starts to climb and will hit 220-230' within another 5-6 miles. Due to the cam, it idles at about 900rpm.

I have run radiator flush twice and am using a 180' t-stat. I'm wondering if my fans/shroud aren't the issue.. Any suggestions? Thank you.

Mike

image.jpeg

 
Last edited by a moderator:
Has it always had this issue, or just recently started?

If just started, inspect and/or replace the radiator cap and see if it still does the same. Could be bleeding off pressure, and lowering the boiling point. The cap to rad neck seal or spring could be bad. Actually, anywhere that there is a pressure leak can lower the boiling point (ie. head gasket, freeze plug, etc.).

Is it losing coolant at all?

Boiling over, or just getting a high reading?

Engine pinging when hot?

Was the thermostat replaced with a CORRECT Cleveland unit? Lots of info floating around on the internets about which one and why. I believe a Robertshaw brand is preferred, but don't know the part number.

Personally, I don't think those fans are taking advantage of the whole core. Look at the design of a stock belt driven shroud and fan in comparison... draws from the whole core, not just 2 circular areas. There's no free air flow going on.

Also, I'd consider a thermostatic switch for the fans. No need to run them from the get go.

 
Last edited by a moderator:
Just checking, the fans are drawing air in and not pushing the air outward. Its easy to reverse the fan wires. Get a small piece of tissue and place it in front of the radiator, it should be drawn and stick to the front, if it doesn't the fan is running in reverse.

Has the car been running ok up to this point and just recently started to overheat? Any work done recently?

 
Has it always had this issue, or just recently started?

If just started, inspect and/or replace the radiator cap and see if it still does the same. Could be bleeding off pressure, and lowering the boiling point. The cap to rad neck seal or spring could be bad. Actually, anywhere that there is a pressure leak can lower the boiling point (ie. head gasket, freeze plug, etc.).

Is it losing coolant at all?

Boiling over, or just getting a high reading?

Engine pinging when hot?

Was the thermostat replaced with a CORRECT Cleveland unit? Lots of info floating around on the internets about which one and why. I believe a Robertshaw brand is preferred, but don't know the part number.

Personally, I don't think those fans are taking advantage of the whole core. Look at the design of a stock belt driven shroud and fan in comparison... draws from the whole core, not just 2 circular areas. There's no free air flow going on.

Also, I'd consider a thermostatic switch for the fans. No need to run them from the get go.
Click to expand...
Well, there were a number of issues that kept me from really driving the car (wiring, rebuilt the carb and trans, new power steering pump, etc..) so I haven't really driven the car, but when I did, it always seemed to run on the warm side. I just never drive it much. Just a few miles here/there. The t-stat is a Napa part but looks identical to the "factory" Cleveland part except it's a 180'. As for coolant, it's not losing any at all.

I've always been curious about those fans. They aren't running in the wrong direction but the don't seem to pull as hard as the fan on my '95 Mustang GT. Is there a magic number (depth) that the fan shroud should be from the face of the radiator?

 
Just checking, the fans are drawing air in and not pushing the air outward. Its easy to reverse the fan wires. Get a small piece of tissue and place it in front of the radiator, it should be drawn and stick to the front, if it doesn't the fan is running in reverse.

Has the car been running ok up to this point and just recently started to overheat? Any work done recently?
Click to expand...
As I explained to MotoArts-

No recent engine work. I've always wondered about that fan setup and shroud. My '95 GT had a supercharged 393w making over 550rwhp and I just used the factory fan/shroud and a Fluidyne radiator. It only went over 195' if I was in the boost for a bit but would quickly return to 180-185'.

 
Your fan set up is not utilizing about 25% of the surface area of the radiator, so its possible that is contributing. It might also be a malfunctioning temperature sending unit. When it hits 230 degrees are you seeing any other signs of overheating? Kind of a long shot, but if everything else checks out it might be that.

Scott

 
Your fan set up is not utilizing about 25% of the surface area of the radiator, so its possible that is contributing. It might also be a malfunctioning temperature sending unit. When it hits 230 degrees are you seeing any other signs of overheating? Kind of a long shot, but if everything else checks out it might be that.

Scott
Click to expand...
Thanks.. I'll check out the sending unit/gauge and the radiator cap. Then I'll look at a better fan setup. I've always used oil coolers but right now I think it might just be a bandaid.

 
Your fan set up is not utilizing about 25% of the surface area of the radiator, so its possible that is contributing. It might also be a malfunctioning temperature sending unit. When it hits 230 degrees are you seeing any other signs of overheating? Kind of a long shot, but if everything else checks out it might be that.

Scott
Click to expand...
Thanks.. I'll check out the sending unit/gauge and the radiator cap. Then I'll look at a better fan setup. I've always used oil coolers but right now I think it might just be a bandaid.
Click to expand...
https://www.amazon.com/gp/product/B003PB9S8G/ref=oh_aui_detailpage_o06_s00?ie=UTF8&psc=1

https://www.amazon.com/Painless-30140-Dual-Fan-Controller/dp/B003XLE2LQ/ref=sr_1_1?s=automotive&ie=UTF8&qid=1473049679&sr=1-1&keywords=f5+dual+fan+controller

Install correctly and you'll be amazed.

 
Lincoln Mark VIII fans pull more air than just about everything else, but they are popular and hard to find. Ford Taurus are also supposed to be nearly as good, as well as Contour fans.

 
Lincoln Mark VIII fans pull more air than just about everything else, but they are popular and hard to find. Ford Taurus are also supposed to be nearly as good, as well as Contour fans.
Click to expand...
Cool.. Thanks. Is that more than the '94+ fans? I have been reading they are pretty good..

 
Lincoln Mark VIII fans pull more air than just about everything else, but they are popular and hard to find. Ford Taurus are also supposed to be nearly as good, as well as Contour fans.
Click to expand...
Cool.. Thanks. Is that more than the '94+ fans? I have been reading they are pretty good..
Click to expand...
Any specific year I should look at?

 
I've always wondered about that fan setup and shroud. My '95 GT had a supercharged 393w making over 550rwhp and I just used the factory fan/shroud and a Fluidyne radiator. It only went over 195' if I was in the boost for a bit but would quickly return to 180-185'.
Click to expand...
I'm thinkin' you answered your own question there.

That's what I was getting to.

Borrow a cap, any cap that fits the neck... see if it does the same. If so, chuck those fans or build shroud sorta mimicking a stocker (venturi shaped) for them. Personally, I prefer a simple clutch fan with a stock shroud like the 5.0's have.

Not knowing what CFM those fans are is another thing to consider. They still may be inadequate, even with a better shroud.

Just my opinion, your mileage may vary.

 
From the hail Mary department: Have you checked to see if there is a small squared edge (part of the head gasket) sticking out from between the block and the heads at the front of the engine? Most have this feature so correct installation of the head gasket can be checked without removing the heads.

As I said, a hail Mary guess. Chuck

 
I'll check those items and will get back.. Thanks everyone..

Mike

 

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