I have been struggling with a cooling issue for aver a year now and cannot figure this out. I have a 1998 ram 1500 5.2 4x4 5spd. It runs at about 180 and can idle with the AC on in the summer without getting above 210 all day. When ever I go up a long steep grade the temperature gauge climbs quickly and pegs, warning lights come. The coolant level never goes down and it doesn’t boil over or steam. It quickly cools down as soon as I begin heading downhill or flat road. I have a 180 degree thermostat in but I began having this problem when I replaced it last year.

Things that I have replaced to try to solve this:
Coolant sending unit
Fan clutch
Thermostat
Bled air from system by parking on an incline with rad cap off.

Is it possible that the water pump is not performing well enough to move water through the systems when the vehicle is on a steep grade with the nose up?
I know that the Cat converter is bad from the rattling sound it makes, Can backpressure cause and overheat like this if the engine is under load? It does not pull hills with much power but my last truck was a Cummins 5.9 so I would expect much less performance here.

 

I would say it's the Cat. Under load that puppy will cause your back cylinders to heat up quick. I'd hollow it out and see if it helps.

 

Thanks. I will give that a try. Is there a way to do it without cutting the cat open. can I break it up from the back and suck out the honeycomb with a shopvac?

 

i would just guess its not the cat. as a test, you can temporarily remove the front O2 to allow a pressure release. ignore the cel. if you get an improvement in temp, then its the cat. if you don't, i'd look elsewhere.

i'd guess its a radiator flow problem. to verify that, check the temp of the radiator return hose. it should be fairly cool, possibly cool enough to hold with your hand.

another possibility is that you're getting a lot of transmission heat into the radiator, contributing to poor engine cooling.

regarding cat. yes, you can cut the pipe behind it and bash it out with a long rod and hammer. don't get it stuck. remove O2 sensors before bashing. cover muffler with duct tape and move it aside, and let engine exhaust blow out the cat.

 

Back pressure from a clogged cat can cause overheating, especially of the rearmost cylinders, and especially when the engine is loaded and flowing a lot of exhaust. If you're driving around with a known bad cat, you're putting your heads at risk of cracking -- fix that and hope they're not already cracked. Also check out the plenum gasket and PCV valve in case they're the cause of the cat failure.

After that, take it out and do what you've done before to make it overheat. If it still overheats, flush the heck out of the cooling system.

 

I'm going to cut out the cat tonight for safe measure until I can replace with a high flow cat. I did feel the radiator when I got home last night and there was a noticeable cold spot on the drivers side lower corner that took up about 25% of the surface area. I flushed the radiator last year when this problem first started but it appears that I may just need a new one. Any tips on what NOT to buy. Seems like there are a lot of options out there ranging in price from 75$ to $250?

 

Don't buy cheesy Chinesey. The low-buck radiators are all cheesy Chinesey.

 

the cheap radiators more than likely come from mexico, as do most all auto parts. i love cheap radiators. because they cost a ****load less....

i think the cheap ebay radiator and the more expensive one from napa are likely the same damn parts. one is just a lot more expensive than the other.

 

1800radiator supplies most of the parts stores around me.

 

I gutted the cat and welded up the hole I cut in the side as best I could. It is really loud now. Anyone have any tips to bring the volume back down after gutting the cats. i was thinking of wrapping it in some exhaust fabric then putting the heat shield back on?