Coolant airlock?

[Omegadog]

Hey guys. 1st time poster. Great squarebody source you have here.
I have a '84 Silverado with a 305 /auto and 700R tranny. GM intake(with riser plate) and 4bbl Edelbrock. 180 degree t-stat(tests fine), all new hoses and water pump. New heater core. Top heater hose to intake and lower to radiator. Freshly shaved heads and valve job. I flushed and flushed the system and after a lot of reading on how to properly fill with coolant I can't keep it from over heating after 10 mins or so. The lower radiator hose stays cool even after the t-stat opens. I did get it to prime properly and stay at normal temp with straight water and no t-stat just before I drained, installed the t-stat and filled with coolant/water. Getting pretty frustrated at this point.

After I write this I'm going out there and try jacking up the front end to try to hopefully burp the block after drilling a 3/32" hole in the t-stat rim to help air to escape. It does have a fan clutch but because the lower radiator hose is cool I don't think there's an issue there but I'm going to place a powerful shop fan in front of the radiator.

I've had several squarebodies over the years and never had this much trouble with overheating. Any other suggestions or links that may help? Thanks for any input guys and I'll update and share pics of my truck and the progress of my mild resto.

[Omegadog]

Forgot to mention that I also have a new 12# radiator cap on it as well as a universal overflow tank. After jacking the front end up, drilling a 3/32" hole in the rim of the t-stat and running it it still wants to overheat(220 degrees) after a much longer period of time but it's not pegging up to 260 degrees now . The coolant went from a nice green to a light brown now(again) .  The t-stat is opening and both top and bottom radiator hoses are now warm to the touch. I kept squeezing them to prime them. Running the shop fan in front of the radiator didn't affect or improve the temp.
 I think I'm going to try buying a proper flush kit tomorrow and yes, more antifreeze(again). I'm on a very limited budget for this project buggy and it's really nickel and diming me to death.
Any input, suggestions etc. would be again appreciated.

[FlatBlack77]

is it possible you got a reverse flow water pump by accident?

both upper and lower radiator hoses should be hot to the touch not warm. you shouldnt be able to wrap your hands around them if the engine is over 200 degrees the hoses should be aswell.

are you using the stock tempature gauge? maybe it is bad. buy a digital thermometer or barrow one from a freind(or buy one use it and return it). use it to get an accurate tempature reading on the engine and the hoses.

[Jspeed1987]

I have a suggestion.  with water only in the system and the truck up to temp turn the heater on. Check for heat should be blowing nice and hot. 1st. If it is not hot I would look at the water pump could be reverse flow. I've even seen a serpentine belt be installed wrong turning the pump backwards. 2nd if the heat is blowing nice and hot. Pull the upper and lower radiator hoses. Put a water hose in the top. you will be checking the radiators for blockage make sure your getting good flow from top to bottom.

[Irish_Alley]

why did you replace all that stuff?

[1967KaiserM715]

Run your hand across radiator top to bottom, should get warmer towards bottom, but still very warm. Any cold spots are clogged areas, and this means coolant may not be circulating.  One trick I do is use a clear hose from water pump heater hose connection, and run it to top of radiator, it should not  spill over, if there's no flow, that's another issue. If it does spill over, the radiator is too clogged to function properly.


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[Omegadog]

Thanks for the replies fellas.
Irish_Alley- I replaced all those parts because I'm doing a mild restoration anyways and started with a bad heater core and I wanted to replace the water pump so that I would know that it wasn't part of the problem. The 305 came from another unknown vehical and I don't know the history but it was overheating when I got it. The lower radiator hose was collapsed and the rad cap spring tension was bad etc. I shaved the heads and had the valves done because I wanted them crack checked. The aluminum intake manifold was cracked and needed replaced and while I was in there I wanted a good place to start eliminating possible future issues with the top end.

FlatBlack77- I got the water pump from oreillys and I took the model # back to them and they could not tell me the flow direction. This is a non-serpentine application. The hoses are warm but not too hot to the touch. The heater is blowing 133 degrees at temp with a digital infrared thermometer. The head surface temps are around 170 degrees on both sides and the intake is around 150 degrees at temp. I may very well have a bad gauge or temp sensor. I might as well replace the sensor to see if it's that. The water temp on the top of the radiator without the cap on is only 130 or so degrees which I thought was odd.

1967KaiserM715- Thanks for the suggestion. I will give that a try today.

I'll update if I get anywhere with this or have more info to add. Thanks again guys!

[VileZambonie]

I would suggest you perform a combustion leak test or cooling system pressure test to start.

[Jspeed1987]

 Something else to on my 79 Chevy that I have the coolant temp sensor is near the exhaust manifold on the head . It had a single wire going to sensor every time It got warm it would short out on the valve cover. Had me scratching my head for a while

[Omegadog]

Just an update. I replaced the radiator which was definitely clogged I found out when I took it to a radiator shop. They said it was opened up in the past and they recommended to not mess with it. I also replaced the fan clutch and the the gauge still goes up to 260 degrees after running it for 15/20 minutes. The heads only show 160 degrees and 145 on the intake manifold with my infrared thermometer which makes me wonder if it's the water temp sensor or the temp gauge. I'm going to replace the sensor 1st and if this still pegs out I may have to buy an under dash temp gauge. I did notice that the fan is 6 inches from the radiator and I may need a extension bushing. Anyone else went through all this crap?

[Irish_Alley]

I would suggest you perform a combustion leak test or cooling system pressure test to start.

[Timberwolf]

I'd go with the system pressure test first, then consider that some 305 head castings were prone to cracking.

[Irish_Alley]

I'd go with the system pressure test first, then consider that some 305 head castings were prone to cracking.

[Omegadog]

When I pick up a new temp sensor I may rent a compression test kit and I'll report my findings later. The heads were magnetically crack tested(at least I paid for this) before they were shaved and the valves were done. I suppose I could rent the coolant pressure test kit too.
The top and bottom hoses are both hot to the touch now and the top hose is hard keep your bare hand on. Looks like I'm getting a good flow cold and hot. Again, I'm only reading 160 degrees on the heads and 145 degrees on the intake manifold when hot and the gauge says 260+ degrees. Exhaust headers do read 450+ degrees. I'm no mechanic and I don't know what the norms are for these temps. I'm using a Fluke infrared thermometer. When the gauge is pegged after I shut it down I took a wet rag and popped the radiator cap and it only puked a little water and was able to easily take it all the way off. When I took the temp at the top of the radiator it was only 130 degrees! The front of the radiator is cool to the touch where I could touch it.
I don't want to sound paranoid but even though I don't think that I am really overheating now, I don't want to take the risk of overheating again. What do you guys think?. AKA...HELP!!!!

[Irish_Alley]

could be a good possibility that the sensor or gauge is not working right. but i wouldnt start tossing parts without testing them