Continued overheating issue
 

As some of you may recall, after three years of restoration on my 1953 Chevy pickup, I encountered some major overheating issues. For a reminder to folks who followed my adventure and for the folks who are reading this for the first time, let me give you a brief background on the truck and the issue,

The Truck
It is a 1953 five-window with a 1959 261 cubic inch straight six engine. It also has a 1957 McCulloch supercharger from a 1957 Studebaker Golden Hawk and a Vertex magneto.

Due to the mounting location of the supercharger, I had to have a custom aluminum radiator constructed to move the lower outlet from the passenger side to the driver side. As a result, the lower rad hose goes from the lower drivers side, under the oil pan and up the side of the block to the water pump inlet. Also given the squeeze of the engine in the engine compartment, there is literally no room for a mechanical fan attached to the water pump. I have electric pusher fans on the front side of the radiator.

The Issue
I cannot drive the truck more than a few miles before I see the water temp gauge creeping up to 200 degree and higher. I have to pull over, open the hood and let the engine cool down for 20-30 minutes to drive home or to the destination.

My first attempt included removing the one 3,000 CFM electric fan and replacing it with three 2,000 CFM fans. I also swapped out the thermostat from 180 to 160 degrees. I replaced the lower rad hose with one with an internal steel spring to avoid it collapsing and restricting water flow. I also lowered the temp setting on when the electric fans would kick in to 150 degree. Lastly, I installed an air damn under the radiator to create a low pressure when driving to help get hot air out from the engine compartment.

I also installed a digital temp gauge to ensure I was reading the gauge on the electronic instrument panel, since it is only marked 120 - 200 - 280. I wanted a more accurate reading of the temp.

The Result
In short, no change. I can drive a few miles further than before, but once I stop at a traffic light the temp gets to over 200 degrees and will continue to climb if I didn't pull over.

Today, I ran the engine at idle in the shop and used my temp gun to calibrate the electronic gauge progress. At idle (about 1,000 RPM) the engine got to over 200 in about 10-15 minutes. At 210, I shut the engine off, let the electric fans continue to run, and put my large shop fan in front of the truck to cool things down.

On the advice of a friend, I let the engine get up to over 160 with the radiator cap off to watch to see if I could tell that the thermostat opened and water movement started. At 160 'ish I did see the movement of water, not terribly fast, but it clearly was moving. His next suggestion, was to pull the thermostat and see if removing the restriction resulted in any cooler operation. Since I'd have to remove some coolant to do that, I decided to try all of this first.


I am at a total loss on how to proceed or what to try next to resolve this major issue.

Could it be the thermostat?
It is a new water pump? The belt is not slipping and its turning properly.

Thoughts.

Re: Continued overheating issue
 

Sounds like a restriction, so removing the thermostat would be first.

Re: Continued overheating issue
 

If you have an old thermostat sitting around take the thermostat part out of it and just put the shell in. That acts as a restrictor that slows down the flow but never stops the flow.

The air dam to direct air through the engine compartment at road speed may be actually messing up with the flow of air through the radiator at road speed, All air going into the engine compartmemt should go in through the radiator, not over or arouund or under it.

I've seen guys thinking they were cutting a fat hog by taking a hole saw and putting holes in the panel that holds the hood latch for looks or thinking they were increasing air flow but they were giving the air an escape route up and over the radiator. The same with later model guys who leave panels off on the sides of the radiator.

If the engine is cooling reasonably well at road speed and the temp goes up sitting and drops back down when you get up to road speed it is an air flow issue. Been there, done that own the shirt with my 48 and the little bitty 15 inch fan that only covers about 40 % of the radiator. One of the reasons I bought the GMC aluminum radiator for my 48 is to get an extra inch of fan clearance and let me run more fan blade. I won't be able to run a larger fan but will buy a shroud for it or use one of a 1-1/2 ton truck I have to pull air though the whole radiator. I've also been looking at an auxuillary pusher fan to help the mechanical fan. Should have offered to sell my never used Aluminum Chevy radiator to Nvrdone when he needed one. That's a beast of a radiator.

I don't think that moving the outlet to the other side on the bottom is any issue, it just thinks it is a Ford radiator but cooling wise it is coolant in tht top, down through the core and out the bottom into the hose and on to the water pump.

Re: Continued overheating issue
 

At road speed, I see the temp coming down, so I don't think the air damn is creating an issue there.

Any thoughts on if the water pump is strong enough to pull 36 inches of water (length of lower rad hose) under the engine and then back up to the water pump inlet?

Re: Continued overheating issue
 

I went thru alot of the same problems on my '49. I removed the t'stat and that improved things. The best way to check a t'stat that i've found is to put it in a pan of water on the stove (dont let your wife catch you) when it gets to about 180 you should the t'stat start to open. The other problem I had was that the water pump wasn't moving coolant even though it was new. If you have a slow coolant flow I would suspect a bad water pump.

Re: Continued overheating issue
 

Have you looked into higher volume water pumps.
Here’s one of many

https://flowkoolerwaterpumps.com/en-...mmu7o0nkSxA64j

Re: Continued overheating issue
 

Have you checked the temperatures of the inlet vs outlet hose of the rad?

It does sound like either a coolant flow issue, or an air flow issue.

Re: Continued overheating issue
 

You could also look into adding a disc to the impeller in the pump.

https://www.jalopyjournal.com/forum/...-disc.1230827/

Re: Continued overheating issue
 

Can't remember if we went over this in the last thread - stock pulley sizes?

261 has a vertical steam passage between cylinders that 235 does not, are you running 235 or 261 head? head gasket?
235 heads can evidently be drilled for the steam passage, but you need to run the 261 head gasket, not just punch the extra holes into 235 gasket. (disclaimer - this is Internet information I am parroting, in a couple weeks the 235 head comes off the 261 in my son's car to look into coolant bubbling in rad issues and we may learn more first hand)

Tuning makes a difference.
What is your timing set to, initial and with all advance?
Do you have a air/fuel ratio gauge to see how rich or lean it is?

I think the Vertex mag is only mechanical advance, no vacuum. I am no engine builder, but that seems like a compromise for general street driving. you need to add some advance once the engine starts, but not too much, then add more as RPM builds, that is why distributors have a combination of vacuum and centrifugal advance. Boats and race cars often do away with vacuum advance, they are optimized for power at certain RPM ranges, not street driving.

My 1952 with 250 6 runs much smoother and cooler since I got the mid range of the advance curve cleaned up by swapping HEI advance springs and was able to lower the power piston in carb to run leaner. (10% fuel economy gain too)

I'd want to know what your current timing was before starting, but I'd consider taking some out to see if the heating issue changes. You probably loose some throttle response and top end power doing that, but if it helps with cooling the next step is to dig into vertex advance tuning possibilities or consider swapping to a small cap HEI distributor with adjustable vacuum can and an assortment of advance springs to play with.

Re: Continued overheating issue
 

looking back at pictures of your engine, you have a lot of stuff right behind the rad. Restriction in airflow after the radiator? Do you get much wind coming out under truck or from hood louvers when fans are on?

Have you driven it without the hood on to see how it cools?

Attachment 2428962

Re: Continued overheating issue
 

kinda thinking along the same ines as leegreen. the front of the engine and the accy's may be blocking a lot of the air flow possibilities for the fan to overcome at idle. there is really only the 2 spots on the lower areas for easy flow through, the upper area needs to go up and over, then find a way out from there in order to get out the bottom or through the hood louvers. I am also curious how it does for engine temp with no hood.

Re: Continued overheating issue
 

FYI, it overheated in my shop with the hood open and a 24 inch shop blowing through the grille on high. I could feel the air flowing around the engine and up out of the open hood.

I truly suspect it’s either the thermostat being a restriction or the inability of the water pump to pull 36 inches of water from the drivers side lower return outlet, under the oil pan, and then up the passenger side of the engine block and then make a 90 degree turn through the supercharger bracket to the water pump inlet.

If I can narrow it down to the water pump, I’d consider installing an inline supplemental inline water pump.

Re: Continued overheating issue
 

At idle possibly water pump has inadequate flow. A supplemental pump or high flow replacement may help out. Higher engine rpm would cause better flow from original pump simply due to the faster pump speed. Smaller pulley on pump may also help as it would overdrive the pump.
You have nothing to lose by trying a smaller pulley or installing a larger inlet tube (lower rad hose) or a supplemental pump.

Re: Continued overheating issue
 

Any one have any experience with the supplemental pump? I see all kinds on Summit from $140 to $900. I have no plans for a $900 model, but I'm not sure what to look for in terms of additional flow capacity.

Re: Continued overheating issue
 

Does running the heater fan at full make any difference? Water there should circulate independent of thermostat and rad. Heater core should just about cool it an idle, at least on a cool day.

Using a IR temperature gun, does the upper rad tank get to the same temp as thermostat housing once thermostat opens? It should, quite quickly if pump is moving coolant properly. If not try without a thermostat

Is lower rad hose about the same temp for it's full length? It should be. If hose is not collapsing or pinched, I'd be less worried about length than how far the pump has to lift the water. Which is stock-ish for you.

What is temp difference between upper and lower rad tank? It should show a decent difference.
From side to side across the radiator surface? In case some passages are blocked

If you run water from a hose over radiator does it still overheat?

Re: Continued overheating issue
 

Yep, tried running the heater full blast. The only difference it made was to make the passenger compartment unbearable in 95 degree weather with no AC.

Thermostat housing and top of rad are almost the same temp at peak.

I know the lower rad hose isn't collapsing as the 36 inch length of it has a steel spring integrated its entire length. Since its largely under the truck, its difficult to get a temp its entire length. The part of it I can see under the supercharger, before it make the 90 degree turn into the water pump is significantly cooler (130 degree when the thermostat is open and its at 180++) But its impossible to tell if water is flowing rapidly through it.

Re: Continued overheating issue
 

Well I went back on your threads and if you still have that mess of a cover holding your fans I am going to hurt your feelings and so be it but take that air blocking mess off and use bars to hold the fans so air will flow though the whole radiator when the truck is moving at speeds and you may need to run one big pusher with a couple of small pushers to get the most radiator coverage. That would work on the back side to pull air though the radiator but blocks too much air from the front.
With the air dam pushing air into the compartment and that mess blocking air flow you have created your own overheating setup as electric fans don't normally push or pull enough air when you get up past 50 or so and the radiator relies on natural air flow.

Re: Continued overheating issue
 

No need to hurt my feeling, I heard you and the others the first time. While I have three fans mounted in the same orientation as my mockup. I used 1 inch aluminum strap mounted on each side of the rad and mounted the fans to these two straps.

Attachment 2429029

Re: Continued overheating issue
 

OK I didn't know that you had changed it.

Engine compartmen air flow can be checked by removing the hood and seeing what happens. That would be a test of air flow or no air flow with the hood on and not for a hot rod look.

I've got 120 louvers in my hood and on a hot day you don't get any cool air through the cowl vent at road speed.

Re: Continued overheating issue
 

Guess I need to go back and read all the way through the threads as you did post that you changed it and that isn't blocking air flow to the radiator at 60 in the least.

Re: Continued overheating issue
 

While I could remove my hood, I'm not sure I see the point given that at idle (1,000 rpm) in my air conditioned shop (door open a foot or so) with a 24 inch shop fan blowing into the grille, the car overheated in less than 15 minutes.

Certainly driving around would be at more than 1,000 rpm and at the city speeds I've over heated at (30 mph) I doubt more air got into the grille than that heavy duty shop fan did.

If I wasn't traveling this week, I'd go to Summit and buy an electric supplemental water pump and see if more water flow makes a difference.

Re: Continued overheating issue
 

1000 rpm idle is a bit fast, at least for a stock 235/261. I'd be checking carb, looking for vacuum leaks and checking timing, 750 idle RPM would be my target. not being able to turn down a fast idle implies a lean condition, lean runs hot, so does timing being off

But your engine is not close to stock, maybe 1000 rpm idle is what it needs.

Does the rad show a temperature differential between tanks? and is it getting hot all the way across the fins? Have you confirmed the thermostat opens properly or take it right out? I'd check stuff like that before adding extra pump

Re: Continued overheating issue
 

I'm not sure that a supplemental pump will help. If the coolant flows thru the radiator too fast it will not cool down. I would install some kind of restrictor in place of the t'stat and then check the temps at the top and bottom hoses.

Re: Continued overheating issue
 

I am not sure if this has been mentioned and is even worth the saying but those are pusher instead of puller fans, right? I.e. the fan spinning direction is pushing air through the radiator instead of pulling it out towards the front.

Re: Continued overheating issue
 

realized my comments on vacuum advance maybe misplaced for this engine ;)

What did it have for cooling fans when you got it? Was it known to have run well for previous owners? The hood louvers had some effort put into them and may imply ongoing cooling issues

I'm still not over it being a possible tuning issue, how is fuel pressure regulated to stop it going lean as it builds boost? Do you have a A/F gauge to see how that is working out?

210 is hot for a 235/261 but not unreasonable for a newer EFI engine. I assume you are running a pressurized system and antifreeze that is not boiling at that temperature. Does the engine builder have any advice on target operating temperature?