Hi all,
I was out of town recently and had a guy who owed me some money take my truck to a tranny shop for the c6 rebuild I'd been needing. It was a perfect situation as I can't be without my truck. When I got home a day later it was ready and I went and picked it up by meeting a friend of the friend who also is a mechanic but he said he wasn't the tranny guy. I had this guy who brought me the truck do some repairs on the wifes Honda and he knows his stuff.. I found my new tranny to be running great and strong but leaked around the pan and possibly the shifter lever entry place. He casme to the house and confirmed a small crack on the block and he tightened the bolts on the pan and it barely leaks now. This whole time I still am waiting for a invoice with a warranty or something. They're 'working on it', It isn't the best practice doing business this way but I do know that the transmission is new and works good. I found that the guy who did this also installed an external transmission cooler with rubber hose to and from the transmission. He undid the lines from the new radiator and ran hoses to the external cooler they had mounted to the front of my new radiator. The fittings at the radiator were plugged. Here's my dilemna while waiting for some kind of word from the transmission mechanic I need to know if I should change the fluid after how many miles? Also, now that it's getting hotter (106 yesterday) the temp guage is showing barely on the right edge of normal. It's usually right around the M in normal. It's overheating basically. It's tied to the weather. I'm about to replace the water pump because it is making the first signs of going out. It's not weeping but it's starting to growl. The external cooler is actually blocking my radiator and this hasn't been a problem until the hot days. It is currently being driven 60 miles a day and suddenly it's getting hot when the weather gets extra hot. Should the transmission cooler lines go to the radiator then to the extrernal cooler? Why would they do this? Also, fluid is still pink but there's 2000 miles if not more on this new rebuild. It wasn't the original but a rebuild swap. I'm okay with it once I get a warranty in my hands but need to know if the radiator is being compromised by the external cooler mounted in front of it. Both radiator hoses are hot, and the coolant doesn't leak. The thermostat might be stuck open (can it?) as I don't see the guage cycling as it should when it works properly. I'm really bummed about how this is going but it is running good. I hate to mess with the thermostat and waterpump when it's not leaking but I may have to. I have all the parts and will but should I first try to run the cooler lines in series with the radiator, being a new radiator which wasnt really cheap, or used. I'm still waiting on this to resolve with the mechanic, but I need to be operational and would like some advice on the fluid change mileage and the routing for the cooler. Thanks for reading this long post. Thanks in advance for any input. BTW 1980 5.0 c6 2wd

 

I have said this 100 times, and I will keep saying it: Do not spend any money on fixing a overheating problem that you "think" you have from the factory gauge readings. If you really want to know what the temperature is, get a real gauge and mount it under the dash. One of those cheapy mechanical ones from the store will work. They usually last about 5 years but they are better than the factory gauge for diagnosing problems and actually how hot the engine is running. If the new gauge says you are overheating, then work on it.

They put the external oil cooler on it for warranty purposes. Many rebuilt transmissions are ruined by junk from the old trans that is inside the radiator cooler. Usually shops have special cans of stuff and take a lot of time to clean the cooler out, they must not have this and instead put a new external cooler on it. The fluid needs to be squeaky clean, and contaminants from the old transmission will ruin the new transmission. It should not affect your radiator cooling. I would not change the fluid, I would not touch anything to do with the trans till the warranty runs out.

 

Thanks for the common sense answer I needed to hear. I'm going to install a guage if I can find one that will fit in the spot that will allow a 'T' for my factory gauge. Or another spot on the block that will accept that long sensor on the one I have but haven't hooked up yet. Thanks for the explanation why and it makes sense now,.

 

You can't put the coolant temp sensors in the tee fitting. You can with the oil pressure sensors, but with the coolant temp sensor, the probe needs to be in the coolant as it's passing by. It can't be up the corner of a tee fitting and get a good reading.

If you have taken some emissions stuff off this engine, it probably has some sensors you are not using and you can use those thread holes for the new gauge. Usually it will be up front on the intake manifold on either side of the carb on a v8.

 

It's a 49 state truck but registered and owned in Cali so...still has to test and so I've not removed any components. I'll have another look, though. I know the thermostat housing has a spot for later models and a burp bolt. I seems like something is on the block in back on top. I'll check my manual.

 

Just checked weep hole is clean and dry but there's moisture in the pits where the distributor electrical plug runs . Back in behind the distributor adj. clamp bolt. It's not puddling but it's always kind of damp there.

 

Minor leaks will not cause it to overheat unless it gets low on coolant.

 

I'm thinking that external transmission cooler is blocking airflow. Last night, after replacing another tie rod end (moog) and test driving after dark, the truck remained cool or normal after getting gas and driving for 20 minutes. But in the heat of the day before replacing that tie rod end I just went to the store for beer. 5 minute drive and pulling into home the factory gauge is showing hot again. Basically, it's running hot when it's hot (100's) outside. When it's just warm (80-90's) it's normal. I ts like putting a hot pad in front of my radiator. It's not just blockage, but blockage with a warm metal thing. It's only running hotter, and may not be overheating since it's still on the far edge of normal. I know factory gauge, but the sensor is new and seems to reliably work in a consistent manner. I'll find out here in a few as I have to drive it uphill for 30 miles.

 

You really do not know how hot the engine is. It's normal for it to run hotter on a hot day in traffic. If it doesn't get over 230F, I would not worry too much. You also need to observe if it's getting hot going down the highway, or is it only getting hot sitting at stoplights. You can observe this better with a real gauge with numbers on it. You can look at different components depending on if it's running hot going down the road, or running hot sitting in traffic.

 

Yeah. I'll get a gauge with temperatures on it this weekend and just unplug the factory one for now.. Thank you, Franklin. I appreciate you always responding to my stuff, for years now. I have a lot of respect for you.