Bremerton, WA... West of Seattle. I ordered a 4 core champion all aluminum radiator that will be here Tuesday. That oughtta cool like a big dog! Thanks for the offer though.

 

###UPDATE###
Okay, got the new Champion 4 core all aluminum radiator, which bolted up pretty nicely into it's new home. Still has issues though. I will break it all down so you can see what all I have done to troubleshoot.

First thing I did was to build a shroud. The original one does not fit so I made a temporary one out of wood and will have a custom aluminum one bent in a couple months. The shroud box sets 1.5" away from the radiator face and has a 16" Flexalite super-dooper cooling fan bolted to it. That booger moves some serious air through the entire core of the radiator... I checked it with a ribbon across the entire face to prove it was moving enough CFM.

Put in a new temp sender to replace the dead one and filled the system with clean coolant. Started the engine and was watching dash guage temp and top tank water flow. The dash gauge showed almost pegged out about the time that the therm opened and water flow was obvious across top of the core. My temp gun said 205 behind the thermostat and 173 in front of it.

That told me right away that the new thermostat was not doing it's job so I pulled it. I ran it again and the gauge still reads high. but not as bad. At an idle, Temp gun shays 195 to 205 degrees at therm housing. Top tank on radiator shows 160 to 185 degrees, bottom tank shows 100 to 140 depending on where you shoot it and the water pump inlet neck shows 190 or higher.

The wate pump inlet neck temp seems way high as it should read approx. what the radiator outlet coolant temp is. I know that the water pump pulls coolant from the intake manifold for the heater core loop which I have bypassed. That loop is wide open and I wouldn't think that it should have much of an impact on inlet temps.

I wanted to test if my engine temp issue had anything to do with the rad fan so I took it for a road test. As I drove faster, the coolant temp went higher, not lower. There is no thermostat in this thing so it should struggle to get to temp at 70 degree ambient temps. The water flow across the top of the core is so fast moving that I had to put the cap on to keep it from sloshing at me.

So, good flow across the core, no therm to slow the coolant down, what seems to be really good temp differential from top to bottom of the core, and still seems to be way warmer than it should be,
'Your thoughts?

 

A few comments... a temp spike on first start after draining the system is pretty common... just getting air/steam out of the system. T stat may be OK. Some engines (like my 400) need the T stat to fully close off the bypass for max cooling. Maybe yours will do better with t stat... I'd try again with correct stat. Also the heater bypass... suggest you block rather than bypass the heater lines if the heater is not installed. Heater bypass is also radiator bypass.

As far as the shroud, its a shame the factory version didn't fit. Factory version fit the factory fan yet was big enough to give good flow at highway speeds when the fan really isn't needed. Could your shroud be restricting air flow at speed? Suggest you repeat the highway test without shroud to find out

And a comment on temp guns... very handy but not so accurate. Much better to measure the coolant temperature directly at factory location. A $15 AP store gauge should be fine as a diagnostic.

 

I'm a little confused by your fan/ribbon/shroud description. If the fan is on the engine side (shroud side) it should be pulling air, not pushing it, so how can a ribbon wave in front of the radiator? Unless I misunderstood. I agree that I wouldn't trust the original gauge...it doesn't tell you anything. A good aftermarket temp gauge is always a good idea on an old vehicle. Don't overlook the simple/obvious...sometimes we have a way of making things more complicated than they really are.......we hope!

 

Update - I took all the advice I got on the subject and started over. I installed temp senders in the intake and in the neck after the thermostat so I could see what the temp differential was during warm up. I put the thermostat back in - a 180 degree one. I put a ball valve in the heater core circuit and reconnected all of that loop. . The water in the engine heated up pretty quick at idle... 3 minutes or so and the therm opened up around 185 at which time both senders agreed on temps. The auto fan switch is set to turn on at 165 sensing from the bottom of the radiator and it would cycle like a normal system would and the temp guage showed 200 degrees. I turned the fan on constant so that was not part of the equation. Temps continued to climb to 2o5 and that is where they stayed. Mind you, this was at idle, fan running like hell. I took it for a road test with basic throttle (didn't keep my foot in ot) and it climbed to 210 and stayed there. I was out for about 20 minutes and temp was steady but still too high. When I parked it, the temp continued to climb to 225 when I shut it off.


My next step is to buy another thermostat and test both of them individually in a pot of water with a good thermometer and see when they actually open as I believe that the one that is in there is either not fully opening or is not opening until it hits closer to 200 degrees. Having the heater loop turned off seemed to make a big difference. Turning it on and running the interior fan full blast did not change the engine temps a bit.


Sound like I am on track? The thermostat and water getting out of the engine seems to me to be where the issue lies. Half tempted to spray water into the face of the radiator while it is running to see if that pulls engine temp down - indicating that I am not getting enough cooling differential out of the radiator on it's own. I have used the temp gun on the top tank and bottom tank and it seems like there is about a 60 degree difference between the two but don't know if I can actually trust that.

 

From what you have said, it sounds like your cooling system is in fine shape and working as it should. Given that, any cooling system is designed to handle only so much heat.

I would be looking at something mechanical causing the engine to run way warm. Three minutes for a cold engine to come up to temp sounds way too quick.

Most electric fans are pushers or pullers. Some are reversible by design, but any DC motor can run in reverse if the power wires are crossed. This doesn't mean the work efficiently. If yours is running "reversed" make sure it is designed for it

Do you have an issue with head gaskets? Try running a compression check and see if everything is OK.

A lean carburetor can cause an engine to run hot, real hot.

Ignition timing that is off, either too advanced or retarded can cause heating issues.

You mentioned the truck had set for a number of years. Any chance a critter built a nest in the exhaust system? A plugged exhaust will make an engine run hot.

Hope some of these ideas help.
Good luck.

 

I love my 3 core champion radiator. It does get warm while at idle but I have no fan shroud. As soon as it starts moving it drops to 190. I got a 97 thunderbrird fan to do the upgrade.

 

That was my thought at first read. Way too quick.

 

I am so scratching my head now.

I have had enough people say the my homemade shroud was restricting air flow while rolling down the freeway so I removed it and installed the fan with angle iron brackets so there was no restriction at highway speed. I switched the fan on to run full time and started the truck. Watching the temps in the intake and at a sender outbound from the thermostat I could see the actual thermostat opening. Intake temp hit 185 and the other guage climbed to meet it. Within a couple more minutes it was 205. I thought... okay, so the radiator isn't cooling because the truck is not moving and the fan is not enough to cool standing still. Took it for a road test and temps did not fall at 55+ mph. HOWEVER, I went over the top of a decent hill and put it into neutral and let the engine idle while I was doing 60 mph and the temp dropped to 180 degrees. By the time I got home though, it had come back up to 210 degrees. That said to me... I need to drive the truck at idle with a 60 mph head wind to keep the temps at 180. Not good.

I thought that maybe the thermostat was reducing the flow through the engine and causing the temps to be too high going into the radiator. I pulled the thermostat and refilled the system with cool coolant and retested. Took a lot longer for the temps to come up but the truck ran at 190 degrees 30-35 mph and 185 degrees at 50 mph. Temps rose to 210 below 30. So here is where I am at - I see it like this... the engine is putting out X BTU's. Lets say as a totally random number that this is 20k BTU. The radiator is only capable at this time of removing 19k BTU. Means that there is a slow gain against the cooling system all the time. That being said, is the engine producing too much heat or is the radiator not removing the heat that the engine is normally supposed to produce?

I did put a light on my timing and readjusted it to 10 degrees. Dogs out at 8 when the throttle is opened so pushed it up a little bit. I readjusted the carb. It was at 1-1/2 turns before and changed t0 2-1/4 so it was not nearly as lean. Figured that would help heat issues if lean operation was part of it. Honestly, the truck runs smoothest with the timing at 12 degrees and the carb adjusted down to 1.5 turns. However, lots of people have said that this could easily cause engine heating issues.

What to do next? I have 4k into this truck and see no end to the bleeding. I would put an engine in it if I knew that would fix the overheat but I am not sold that would resolve it. I am a "how it works" guy and this has me in the weeds.

 

Oh, and BTW, I have had the top end of this motor apart and I put new head gaskets down, of course. With the coolant cool and the thermostat closed, I do not get compression gases pushing back into the radiator that I can tell. Don't believe it to be a head gasket issue. Can't rule out a cracked head but the truck only has 50k original miles on it. I took off the heads because I had stuck valves due to it sitting for 10 or more years.

 

I may have come up with the wild card...


I modded the A/C condenser to be a trans cooler. It is damn near the size of the radiator and I believe runs about 130 degrees when up to temp. That being the case, I have to wonder if that is causing the air going into the radiator to be way too warm. Gonna do some testing and then remove the cooler and recheck. I really hope that this is the answer. It has been a trans cooler since before I tore the engine down to do top end work. Will update again after I do my testing.

 

And you didn't think to tell us that until now?

R.

 

You said you had the top end off the engine. Was the rig overheating before you did the work?
Did you get the head gaskets on the right way?

I doubt the condenser / oil cooler is the problem. Air conditioned trucks don't overheat with the AC working.

 

Huh... well, no. Of course not 'cuz that would have made sense. Actually, I did ponder that being on the radar for a possible heat source but that was in the very beginning and I got hyper-focused on the radiator. I figure this will be a case of KISS and my overkill engineering will be my downfall. Geez I hope that is the case. I'd rather look stupid and solve the case than have it whip my butt.

 

I took the heads off because I needed to do valve work because I had really stuck valves. As far as I know I got the head gaskets on the right way. They appeared to only go on one way as they are keyed on one edge to mate with the intake gaskets and when flipped, the cylinder holes do not line up.


I have never checked what the condenser temp is on an operating truck but I do remember as a kid my dad having to turn off the a/c in his pickup when pulling or the truck would overheat. Don't believe that they put out 130-150 degree heat though. Going to check the condenser core temp while running and see just to eliminate that possibility.