Good afternoon all,

I’ve been doing a restoration on my 1976 F250 supercab trailer special. It’s a 2wd sporting a 460 with a C6. I’ve owned the truck for 45 years. About 10 years ago I had to lay it up because it giving free showers during the rain. I did a re-cab with full paint and restoration on the interior. Despite only having 67k on the truck I was forced to pull the heads so remove broken exhaust suds.

Now to the issue, the truck is boiling over after 15 to 20 mins of driving. The coolant is reaching 230 degrees. The lower hose is not collapsing although it will without the spring installed..

Radiator is 4 row super cooling that was re-cored once. Took it to the shop and they flow check it and said it was good at 85%.

All hoses have been replaced. Bottom hose has the spring installed

New Gates water pump.

New Motor Craft 195 thermostat installed. Also, I tried a new 160 and 185. Pot checked all 3 thermostats all of them tested as good.

New 13lbs radiator cap. Fan shroud is original and intact.

No water/coolant in the oil and no oil in the coolant. I did one of those combustion gas checks it was negative.

Checked the fan clutch, have resistance when it’s cold and slightly more when it’s hot.

So here is my thoughts, I, have a blockage somewhere in the block. When I pulled the heads there was a blockage in the timing case cover. It looked like green rock salt. I installed a new cover and all new gaskets.

I have verified that I installed the head gaskets correctly; both square corners are up front.

Finally I’ve flushed the system several times, each time when pulling the lower hose to drain the topped off coolant I only recover 10 quarts of coolant.

Appreciated any suggestions for identifying/clearing a blockage, thanks

 

Good Afternoon all,

Yesterday a friend stopped by with his thermal camera. He is a plumper and uses this tool to detect radiant floor heating issues. He looked at both sides of the engine. Flow and temps were consistent. Then he looked at the top and bottom of the radiator, not consistent. Move onto the core and found major flow and temp differences. The image was showing that 70% of the tubes had no flow with a reading of 90 degrees. The other 30% of the tubes had flow and a reading of 190 degrees. The pattern was random and was only the front row..

I've been struggling with this issue for nearly a year.. Last May I had the radiator flow tested and was told that it wasn't my cause of my running very hot. It tested at 85% flow rate.

My truck has super cooling, its a four row 24" H by 26" W core. Therefore i need the Champion MC480. There are none of these available and they are not on backorder due to tariff concerns. Champion suggest that I go with CC480 which is a three row and looks like it will blot right in. This option 1 and cost is less than $400 Option 2 have my radiator re-cored cost is $1,000. Thoughts please..

 

When you said "85% flow" I was like that is not good and your buddy found that to be true.

Question, is this radiator copper or Alum.? What is the new one?
Your buddy may be able to get a HD flush that may eat the blockage. Pull the radiator and set it up so you can flow the flush thru only the radiator.
Years ago I used something to clean a steam to water hot water heater as the water side had scale and this stuff did a nice job of cleaning it.
They were not blocked just would not transfer heat to the water like when it was new.

Now I have used white Vinegar, get it at food stores, on a copper radiator. Put the cap on and lay it flat some place safe not to get stepped on.
Fill it thru 1 of the hose fittings till you see it in both hose fittings and let it sit for a few days to do it's thing.
I did not set up a pump but you could if you want. It did get the white crud off the tubes and then some.
I flushed with water before installing and after in I seen pin holes in the core, the "then some".

I ended up getting a new radiator think from Rock Auto and it is an Alum. with plastic tanks. Been going on 5+ years now without any problems.
Gives you some options
Dave ----

 

Do you have the backing plate behind the water pump?

 

You might consider finding a better radiator shop and having them do what's known as rodding out the radiator. (assuming this is an original copper/brass rad) That's where they take the tanks off and run rods and tiny brushes through the tubes in the core to remove scale and buildup, etc. My thinking is that same green gunk you found in the timing cover is also inside the radiator, clogging up the works. That sounds like someone may have put some leak stop sealer in the system and, as usual, created more problems than they fixed. If boiling and rodding the rad will work, that could save you a lot.

 

Happen to have any pictures to verify head gaskets were not installed backwards? It is mostly the same, but couple ports on lower rear of block could be plugged.

 

X2 on head gaskets being backwards. Look for the little tab on the gasket that should be at the front. It is sometimes also market "top"

 

Seems like after thermal imaging the entire system... Head gaskets do not seem to be the culprit, however I did not interpret the thermal readings so just speculating. My initial recommendation from the available information is take a pitcher of cold water or even a garden hose and with engine idling and heating up use cold water the spray the radiator and see if the temp comes down or goes unchanged. The results from this water test might be helpful in determining if you have an engine heating problem or a radiator failing to cool problem if that makes sense. US RADIATOR does list a large 4 row for these year of trucks still, in the copper. Good luck.

 

The 385 series has a steel backing plate behind the impeller that often does not come with a new pump. if it's missing you will absolutely overheat.

 

Good evening all,
Sorry I was pulled away form my project. Just got back to working on it. I installed the new three section radiator and low and behold it was the problem. Took it out for two 20+ mile runs and the pin never came off of cold. I didn't have the thermostat installed. It took three flushes' to get clean water.

Today I installed 192 thermostat and new 50/50 coolant, looking positive the pin is between T and E in Temp.

Also discovered that my super cooling rad only has three sections. I had it re cored 25 years ago, I was sure that it was a four section.

Again thank you for all of the suggestions and guidance