Hi All!

I've used the search in the forums and have not found a good answer or similar question to my problem, so here it goes. I went to my truck the other day and found that it had spewed coolant out the radiator with the fan throwing it all over the place. Fortunately, I caught it early and did not have any damage to the engine itself; no overheating.

My truck is a '74 F250 Camper Special and has a 390 with the 4" (or so) thick radiator. I think they called that the Desert Cooling package of something like that. I pulled the coolant from the system, then disconnected the transmission cooler lines. I was expecting a small, but still substantial amount of transmission fluid to drain from both the radiator as well as the cooler lines, but there was no more than a thimble full of fluid spilled in total.

I'm concerned that there was no circulating fluid between the transmission and the radiator. Is this normal or not? If not, do I pull the lines from the transmission, clean them out then install them again? Is there a procedure for bleeding this system? Could there be an obstruction or problem at the transmission that I can check or clean?

I know these trucks pretty well, but the transmission cooling system is one of those areas I've never touched on before. I have a few days before the radiator is back, so I've got time to check other things out while I wait. Given the expense of re-coring the radiator ($600 with the original industrial style core!), I want to be sure that it's all working right when I put it back in. I will probably drain and refill the transmission fluid; change the filter, etc.

What else do I look for while I'm in there? Thanks!
-Mike

 

In general, the transmission pumps hot fluid to the cooler when running. No bleeding required but good idea to check and top up the transmission fluid after changing the radiator and running the truck. The radiator may sit high enough that the trans fluid drains back to the transmission when it is shut off. When I service mine, I get a little oil (a tablespoon or 2?) but not too much.

If the cooler was not working, your transmission would be toast pretty quick.

The radiator shop should check and clean the trans cooler circuit with the re-core... good idea to double check with them.

Good idea to clean and check the trans cooler lines also.

If you are towing or otherwise working the truck hard, an additional transmission cooler is recommended in front of the radiator. Oil should flow from transmission to radiator cooler to auxiliary cooler and back to the transmission for best cooling. I run the biggest of 3 that NAPA sells for Dents.

 

I would guess that 90% of the time the truck is not hauling anything, but may look into adding an additional cooler this summer. From some videos on how radiators are made, I was surprised at how little actual cooler there is for the transmission. I thought it would be much more significant, but looks like it's not a whole lot more than nothing to me; just a tube running through the bottom of the radiator. I would think that the supply and return lines may do just as much cooling as the radiator does in that case.

Glad to hear that you also only get a small amount of fluid coming out of the lines when you have disconnected them. That was my main concern and it sounds like it must be normal.

 

Even though I'm not primarily working on my tranny or radiator, I have tranny cooler line questiones and might sort of hijack this thread - hope it doesn't go to far offtopic ;-)
The heads are at the machine shop at the moment because some valves didn't seal properly anymore and I decided to swap the camshaft to Edelbrock in the meantime what means I' have to take the radiator out.

The first line screwed off easily and I noticed that just 2-3 teaspoons of oil drained from the radiator - seems to be normal.
The second one is making some trouble because the coupling nut is rusted to the line what causes the line to twist and damage when fully threading the nut out. This means I'll have to replace it afterwards.
Please stop laughing now ;-) this might be easy for you, but I'm a Newbee on this and not familiar at all with imperial screw sizes since they are so rare here in Germany...
Can anybody tell me what type / size these coupling nuts are? I have the flare tool but not sure what size of nuts I need to reconnect the line when reinstalling everything.

Thanks
Julian

 

I think they are 1/8" npt. But I am not positive. Might try here:
Transmission Parts | Tools | Fitzall | TeckPak

 

As said, stock is 1/8" pipe thread into the radiator. 5/16" flare on the other end. A well stocked hardware store will have the fittings you need (ACE in my area). The AP store may have them as well. Just take your old and match it up.

Also, at least in my area, NAPA stocks the best selection of steel hard line and related fittings.

 

Thanks al lot!!!

They should fit, I guess: Parker 5 16" Tube OD 1 8"NPT Compression Male Connectors 68C 5 2 New Lot of 8 | eBay

Nobody will sell them here in Germany, so I'll have to order them online from the States...

 

Germany makes it harder! If you have to get her going while you wait, you can probably find 1/8" pipe thread locally. 1/8" PT and an 8 mm barb fitting with a short length of 8 mm rubber hose should work.