Hi Guys,
On my 2003 Dodge Ram 5.7 Hemi there seems to be an interior heating issue. On first cold start the defrost or interior warm starts to come through the vents once the truck starts to warm up temperature wise then goes cold. If I fall the gas pedal and bring up the revs heat starts coming through the vents, sometimes it stays nice and warm like it should, Other times it will go cold while driving. Give it another good rev and some luke warm air will come through then go cold again
Been like this when I first brought the truck. I have since fitted and new thermostat and housing and still having the same problem, I can't seem to bleed her up as there is no bleed screw on the thermostat housing or the water pump housing. I still feel that it needs bleeding as when I leave the truck idling it will throw up a quantity of a coolant out of the radiator.. This suggests to me that air is in the system.
My question is, how do you bleed the system on this 5.7 Hemi.
It does not overheat and I can leave it running for 45 minutes with the radiator cap on and in traffic, the gauge stays pretty much at the halfway mark.
My question is, how do you bleed the system on this 5.7 Hemi.
Many thanks
Peter

 

Sounds like low on coolant.....

 

Thank you, I filled it to the level on the header tank, once the thermostat opened the water level dropped and I filled it until the level was correct.
If the coolant is low, how do I fill it differently to get the correct amount in the system?

 

I elevated the front end. Ran with rad cap off. Let it sit overnight, repeat.

 

getting the front right elevated the highest always makes it the easiest, but they are not a hard system to purge, I've had mine open several times, I just fill it and drive, never experienced air issues like you describe, I would wonder if there's other issues, head gasket, or partially blocked core or radiator, or an external leak failure

You have to understand that the radiator will not always be full when its cold, as the truck heats up it will expand and push into the overflow and as it cools pull some back in, if the radiator cap is leaking and this vacuum seal is broken it will just pull air in, but as it heats it will still expand back out to fill the void with coolant. keep the tank in range and see if it depletes over time

 

Many thanks, great that sounds like a plan for me to try next.
I will let you know the out come next week.

 

You can get a pressure tester from most auto parts stores "loan a tool." Test your rad cap.

 

Thank you, cap is brand new.

 

Hi Guys, here is an up date on this issue. Today on a 11 mile journey I noticed the temperature gauge slowly registering near the 3/4 mark. I stopped and there was coolant under pressure escaping through the over flow pipe. I letter it cool down and filled 8 litres of water and carried on for another 3 miles. She blew out a lot more coolant. The gauge was reading just over the halfway mark.
I then filled nearly 15 litres of water into the system. It was starting to blow it out of the overflow under a lot of pressure, the gauge was reading under 1/2.
The local garage put the truck up on the ramp so we could see where else the water was coming from. Heating inside the truck was working nicely as were all the pipes and radiator hoses. The radiator was hot at the top and bottom plus both sides, the centre part of the radiator was stone cold. I will remove the radiator and have this flushed as I believe it is blocked.
The thermostat was renewed with a hotter one, I think it is 93 degree, the old one was 88. Not sure if this would contribute to thus issue.
When I start the truck, I can hear coolant running through the heater matrix so that suggests to me the system is pumping water through the system?

 

If you can hear it, that also means there is air in the system. How does your oil look? Have you had the coolant tested for combustion gases?