Swapped 5.3L Overheating issue
Swapped 5.3L Overheating issue I swapped a 5.3L into my 81 Chevy C10 and finally (After 2 years) got it running and driving around the neighborhood.
I dont yet have a radiator fan on it but the weather here is around 40*F so it should be able to run quite a while without the fan.
The engine has a newer (~2006) Silverado water pump on it.
It has the factory rear steam vent block-offs and the front steam vents are connected and ran down behind the pump and are plumbed into the back of the pump. I had read about many people doing this with no problem so I went with it for the cleaner look. (I hope that wasnt a mistake)
So I have a brand new water pump, new thermostat, new radiator, new hoses.
I put a formed loop hose to connect the heater ports.
So anyways, when I start the truck up it will slowly heat up until it gets to 240F or so. Reading temps with HP Tuners.
When I filled it I was squeezing the hoses and trying to make sure I wasnt trapping air. I squeezed the hoses with the cap off while the engine was running.
I unscrewed the passenger side front steam vent and let steam and coolant spew out for probably 2 or 3 minutes. Idling, holding 3000rpm.
I would kill the engine then fill the upper hose with more coolant and then top off the radiator.
Still showing hot.
I put the front up on ramps to try to get the air out and it made no difference.
I tried it with the radiator cap on, off, tried opening the vent tube both with the cap on and off.
One weird thing is after I shut it off the coolant in the engine/water pump area makes all sorts of gurgling sounds for about 5 minutes and then it creates a vacuum and sucks the upper and lower hose flat.
Also after running the upper hose is hot and the lower is mostly cold. About 3 or 4 inches of hose by the thermostat is hot but the rest is cold.
With the radiator cap off when I raise the RPMs you can see coolant coming from the upper hose, it is not a ton but for sure some fluid is pushing through.
Looking at the coolant there seems to be some small black things floating around, I'm assuming its junk from inside the old junkyard block.
I know that is a lot of info but I wanted to make sure I said what I've already tried.
Anyone have any suggestions?
Think I could have got a bad new pump? Bad thermostat? Just have a huge air pocket I havent got out yet?
Any help is much appreciated.
I dont yet have a radiator fan on it but the weather here is around 40*F so it should be able to run quite a while without the fan.
The engine has a newer (~2006) Silverado water pump on it.
It has the factory rear steam vent block-offs and the front steam vents are connected and ran down behind the pump and are plumbed into the back of the pump. I had read about many people doing this with no problem so I went with it for the cleaner look. (I hope that wasnt a mistake)
So I have a brand new water pump, new thermostat, new radiator, new hoses.
I put a formed loop hose to connect the heater ports.
So anyways, when I start the truck up it will slowly heat up until it gets to 240F or so. Reading temps with HP Tuners.
When I filled it I was squeezing the hoses and trying to make sure I wasnt trapping air. I squeezed the hoses with the cap off while the engine was running.
I unscrewed the passenger side front steam vent and let steam and coolant spew out for probably 2 or 3 minutes. Idling, holding 3000rpm.
I would kill the engine then fill the upper hose with more coolant and then top off the radiator.
Still showing hot.
I put the front up on ramps to try to get the air out and it made no difference.
I tried it with the radiator cap on, off, tried opening the vent tube both with the cap on and off.
One weird thing is after I shut it off the coolant in the engine/water pump area makes all sorts of gurgling sounds for about 5 minutes and then it creates a vacuum and sucks the upper and lower hose flat.
Also after running the upper hose is hot and the lower is mostly cold. About 3 or 4 inches of hose by the thermostat is hot but the rest is cold.
With the radiator cap off when I raise the RPMs you can see coolant coming from the upper hose, it is not a ton but for sure some fluid is pushing through.
Looking at the coolant there seems to be some small black things floating around, I'm assuming its junk from inside the old junkyard block.
I know that is a lot of info but I wanted to make sure I said what I've already tried.
Anyone have any suggestions?
Think I could have got a bad new pump? Bad thermostat? Just have a huge air pocket I havent got out yet?
Any help is much appreciated.
TECH Senior Member
Joined: Apr 2002
Posts: 6,080
Likes: 17
From: So.Cal.
Disconnect the hose from the steam crossover tube and leave it off while engine warms up, let air/coolant exit from here (use a clear tube to direct it away into a bottle)... if no air/coolant comes out of the crossover tube, you have to unclog it using a length of welding wire, or replace it.
If radiator hoses collapse then the radiator cap is faulty (the vacuum valve is clogged).
If radiator hoses collapse then the radiator cap is faulty (the vacuum valve is clogged).
Disconnect the hose from the steam crossover tube and leave it off while engine warms up, let air/coolant exit from here (use a clear tube to direct it away into a bottle)... if no air/coolant comes out of the crossover tube, you have to unclog it using a length of welding wire, or replace it.
If radiator hoses collapse then the radiator cap is faulty (the vacuum valve is clogged).
If radiator hoses collapse then the radiator cap is faulty (the vacuum valve is clogged).
I think I might eliminate the steam port to water pump setup and try to run it to the port on my radiator. I will make sure the crossover tube is clear and warm it up with the steam tube open again.
Thanks for the help man!
