****edit to add truck info (that might be helpful)*****

Any help would be appreciated... I've got to hit the road in 4 hours and I'm stuck. I've got an '03 ram 1500 quad 5.7 4x4

I rolled into town two days ago just after a check engine light came on and the 'check gauges' light came on, which was in reaction to the temp gauge pegging hot. I had an oil change to do anyway so I just finished up with that, and put a new thermostat in as well. This didn't effect the things at all. I am getting fluctuating temps but all are on the hot side.

I drove the truck to see if it might cool down on the highway and it was actually worse at highway speeds than in town, though both driving types show a high temp. I'm not completely convinced that I am actually overheating. The gauge will peg on hot and performance seems unaffected ,there isn't a hot smell, the engine compartment seems fairly normal. (though I am driving it very little in those temps to keep from doing any damage). Also, there is some gurgling noises in the coolant system when I stop, and I did notice a very small amount of fluid that had escaped the cap, no fluid comes out the overflow line.

I'm assuming I either have air in the system, or my sender unit is out. However, I have no idea where either one of these items are located. Can anyone give me an opinion as to what the problem might be, and if it might be as I suspect, let me know where the bleed valve is located (and the best way to bleed the system) and where the temp sending unit is.

Thanks in advance,

J

 

4.7 or 5.7? 4.7 is bad about air pockets in the cooling sys due to the thermostat location, drill a small hole in the top of the stat to allow air to bleed if there isnt one from the factory. Make sure the bleed is at the top if there is one already there. same for the stat in the 5.7, mine came with a bleed hole in it

 

I'm thinking either water pump or you're loosing system pressure which would lower the coolant boiling point drastically...if there's no visible leak i'd replace the cap. If it's still running hot i'd rent a pressure tester and check for loss of pressure and leaks. If it's stillll running hot you could have a prob with the pump and i'd replace that....and bleed the hell out of it.

 

Thanks, going to go get a cap as I did have a small amount of liquid at the neck of the overflow. The water pump is less than 10,000 miles old.

How do you go about bleeding the system? I didn't see any valve at the thermostat housing. Do you just leave the cap off for a bit while it's running to let the air out?

J

 

Yea there's no valve so you have to do it the old school way. Just put the truck at a slight upward incline (optional but recommended), take the cap off, put the heater on high and warm her up until the T-stat opens. It'll burp and the coolant will drop...keep her topped off. Some systems are stubborn and you'll have to repeat a few times.

When you get the new cap make sure you get a good one...the radiator cap is an underrated and very important part of the cooling system.

 

no dice on the new cap and bleeding. At rest the truck sits about 3/4 hot, and goes up from there while driving, it pegs at highway speeds. This is opposite of what I would normally expect. I'm a bit lost on this one and it looks like I'm stuck for the evening here because of it. (was supposed to be on the road).

Anyone think it could be the temp sending unit? If so, where is that lil bugger?

J

 

Usually the coolant temp sensor is in the driverside head. It is an 03...have you ever flushed the system or replaced the upper/lower hoses? You could have a clogged radiator or collapsed hose. Troubleshooting without seeing the vehicle makes it alot harder...so i'm just throwing ideas out for you to work with.

 

Sounds like the radiator is clogged. This would explain the higher temps on the highway.
Had this problem with a friends 97 Ram. Cooked his 5.2L, so I had to swap in the 5.9L
Still got hot. Replaced the radiator and it never went over 1/2 on the gauge again.

 

Thought I would check in with a follow up to explain what the problem might be in case someone else ends up with a similar problem and finds this post...

It ended up being both the radiator and the water pump. The radiator showed dramatically different on the top and bottom of the radiator. I tried flushing it to no avail, so it got replaced. I also noticed a hairline crack in the neck of the overflow tank so I replaced that as well. I was still getting an elevated temp after this as well (not as high, but still higher than it should be).... so the water pump came next, even though it was only a 4 month old pump. After that was swapped out the problem was resolved.

This was a real pain to track down. I'm assuming I got some sort of solidification of the coolant which clogged the radiator which then spread to the new water pump and bound it up. Just speculation of course, but thats about I could come up with.... regardless, it's sorted now. Thanks for the help.

J

 

Cool..glad ya found the prob.