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Anyone else have any ideas? At a loss here. Driving down the freeway in 4th gear it sits at about 195-200, shift to 5th and it increases to about 215 and will mostly hold there. Bad thing it is only 60 outside and I don't think it will hold there when it is 100.
Well, this doesn't really fit what is happening to you, but have you checked for a plugged radiator? When a radiator is plugged, it will get hot driving down the road, but come to a stop, and the temp drops.
Do you have the 2 heater hose connections on the water pump hooked up to a constant flow heater core. To work properly the LSX water pump heater ports need to have full time flow circuit. The heater ports help cycle the thermostat on the water pump inlet to lower radiator hose.
Couple more things. Are you sure the radiator is actually big enough for that engine? If you have the 480hp version, it is probably pumping out some heat.
Also, I know many of those old trucks came with inline 6 poppers. originally. The radiator support usually had a small hole because the radiator was small. You are not blocking 30-50% of the cooling area on the radiator are you by any chance?
Just a few more thoughts. I have seen these situations many times when I worked in a radiator shop many years ago.
If you idle the truck with the radiator cap off does the water start to flow good when the t-stat opens?
Does your steam ports from the engine go to the radiator?
What is the Y setup on the overflow tank?
When ever i fill my engine with anti freeze now i fill through the upper radiator hose and i never have a problem with air. Yours will be easy to do that way.
It could just be the picture but it looks like your engine is level or tilts a little towards the front on the truck. Don't think that is a problem but they are made to tilt back.
Do you have heater hoses hooked up to the water pump? Looks like it in the pic but hard to see.
If you idle the truck with the radiator cap off does the water start to flow good when the t-stat opens?
Been a few months since I checked and I will check again but it did.
Does your steam ports from the engine go to the radiator?
Steam ports go to the overflow tank
What is the Y setup on the overflow tank?
The Y is for the heater. This was suggested as the best way to plumb it all in since that isn't really an overflow tank but a surge tank I think they are called.
When ever i fill my engine with anti freeze now i fill through the upper radiator hose and i never have a problem with air. Yours will be easy to do that way.
It could just be the picture but it looks like your engine is level or tilts a little towards the front on the truck. Don't think that is a problem but they are made to tilt back.
It does tilt back slightly. I tried for 3 degrees.
Do you have heater hoses hooked up to the water pump? Looks like it in the pic but hard to see.
I do.
In response to Joyridin', The radiator should be plenty big. It is a 4 core for a 500+hp system and I am getting quite a lot of airflow, including that top section showing since the hood on these has a gap of about an inch when closed. The only area of the radiator that doesn't get air flow is that section you can see in the photo so maybe 10-15%.
I finally learned something useful today. I re-routed my steam tubes away from my surge tank and into an adapter in the top radiator hose. I then routed my radiator release hose to my surge tank. This is exactly how my 07 Silverado with a 6.0 is.
Completely cold, I turned it on and pulled off my radiator cap and coolant just pumped out. Seems I have blockage somewhere but I need help on where.
Based on this picture, it would seem my thermostat isn't allowing anything past which I assume is normal when cold and closed but isn't there a bypass? Maybe I am wrong. I have always been able to open my radiator cap to verify flow without an issue. But I have never done it in an LS. Do I have to wait for the thermostat to open before I can verify flow?
Answered my own question. I took my thermostat out to test and can see the thermostat has to be open to see flow. Water pump is definitely working and my thermostat is working properly, opens at 86C or 186F.
That should take care of the problem. You weren't pressurizing the system when the vent lines were going to the overflow and raising the rpm would sweep away the steam voids and temporarily cool down the system. Make sure to get the air out of the system and give it another go.
Frustrating update. Ran the car in the driveway for a while to try and diagnose different temps. When temp on gauge was at 200, temp at top of radiator was 195 and at bottom near hose was at 90. Is this possible? Temp at sensor for gauge was at 188 and at sensor to pcm was 195.
I allowed it to build heat up to 215 and all temps except lower radiator increased proportionally. Then steam started pouring out of the middle of my radiator. No hissing or anything but coolant smelling steam front and back. Guessing I blew a leak somewhere.
It sure seems to me that I am not getting the flow either through the radiator or through the thermostat. Revving the motor cools it down and increases pressure due to faster running pump. Is the logical conclusion that my radiator is not flowing properly?
This is the radiator I was using. Only 3 core but rated to 650hp supposedly.
Do you have the 2 heater hose connections on the water pump hooked up to a constant flow heater core. To work properly the LSX water pump heater ports need to have full time flow circuit. The heater ports help cycle the thermostat on the water pump inlet to lower radiator hose.
You might be on to something with this one. Mine is an older style that does not flow with the heater temp set to cold. Unfortunately it will kill me inside the cabin to have the hot water flowing constantly through the core and I'm sure my a/c won't work well. I may have to figure out how to loop my system during the summer months.
The temp reads on my thermostat housing were very low but I assumed it was just because it was thicker aluminum. I also noticed the 3/4 heater in line was reading about 150 when everything else was 195. All of that might mean my thermostat is not opening.
Wish I had figured this out before blowing my radiator. Now I am dead in the water until I figure out a new radiator. Hesitant to go with another Champion.
Problem solved. I turned my heat to hot and now it will idle and run at 195. Still have to replace my radiator but at least I know what the issue was. Hopefully this thread will help someone else.
Many thanks to all that gave me ideas and especially to 427 zeo6.
Problem solved. I turned my heat to hot and now it will idle and run at 195. Still have to replace my radiator but at least I know what the issue was. Hopefully this thread will help someone else.
Many thanks to all that gave me ideas and especially to 427 zeo6.
Glad you got it figured out. I got a universal aluminum radiator from Speedway and it's been good. They come in various sizes and are cheap...
If you want OEM, I have also had good luck with C4 Corvette radiators. They are super light and the inlet and outlet are size perfectly for the LS engine. If the size works for you, I'd go with that. Also cheap.
12-31-2015, 01:41 PM
