For months now I've heard complaints from my brother during the summer that the truck overheats when its over 100* or when he tries to tow anything. trucks a 99 5.3l and has been babied.

Replaced water pump, thermostat.
Flushed radiator.

I haven't convinced him to thump the cats yet, but he opened one and took a small chunk out and said it was clear, what else can cause high temps?

I insist the sensor need replaced, not like they work properly forever.

 

IMO, radiator flushes are not very effective if a radiator has got clogged enough to cause overheating.

Replacing the radiator or having a radiator shop rod it out have worked for me when a flush made no difference.

 

well at least I have one more radiator vote. I initially questioned it but he wrote it off when he said not long ago it was flushed.

Right now he's on the long shot of the cats are plugged (another persons idea) and is causing heat to build. I see the idea, just not quite seeing it this time.

 

From personal experience, 9/10 a plugged cat will glow in the dark from heat buildup. Easiest way to diagnose that IMO. One silly thing a lot of people tend to overlook is the cap. If it's venting,even just a little, it could cuase a lack of cooling efficiency. Especially under heavy use, like you mentioned.

 

Hey! that has definitely been over looked, I will question him about this one.

 

I was thinking the same thing about the cap or maybe even a small crack in the upper portion of the radiator. Good Luck.

 

dexcool is the devil, Im voting radiator.

In the event he is overheating, use the heater core as an additional heat exchanger, max heat on the floor. It sucks in the summer being hot as ***** in the cab, but it beats walking or blowing an engine

 

Do those trucks have clutch fans or electric fans? If its a clutch fan, maybe thats bad.

 

99% sure its a clutch. I think Chevy is just now jumping on the efan wagon

 

Ive had those fans go bad before, they spin ok at idle but they do not pull enough air at speed to cool it adequately.

 

chevy has done Efans since 2007 in their fullsizes. Ford has them starting on the 2010s

 

When it's warmed up real good see if you can feel a temprature difference between the top and bottom of the radiator. If the bottom is cooler even just a little that would indicate that it is starting to plug b/c that is where all the junk settles. If you have an infrared thermometer that is even better.

But you gotta remember, it is a chebby!

 

I vote for the infrared thermometer. Can tell you a ton about what's going on. For as cheap as you can buy them today, I wouldn't be without one. If Chevy already used E-fans by then, and they're both running (I think they used dual fans) and the coolant is not dropping temp. enough by the time it goes back into the block, you know either clogged or worn out, assuming the cap has already been pressure checked by now. (yes, radiators DO wear out, if the fins get loose on the tubes or internal erosion thins the tubes too much, which cause it to not exchange the heat well enough) Ford always used better radiators than Chebby. Less trouble with aluminum than the old copper though. A lot of other things that can cause overheating on a 100+ degree day though. 1st thing is that big "bow tie" in the front, get rid of that and put a "blue oval" in it's place and your overheating problems will go away!

Also, get rid of that 5.3 and put a 5.4 in it's place will probably also solve the problem.

 

I thought he replaced the mech fan clutch. Will have to send a txt and see what he has done. I think radiator as well, since he "flushed" with a garden hose is what I was told by my mom. I need to grab some prestone radiator flush and hand it to him.

Im not sure what to do with this truck since he just went to pick up a new GMC diesel (2008?)

I've tried getting him to use a temp gun, he has one, but I've never heard he used it like I told him to.



it gets better, his wifes 2008 overheated pulling a 23ft toy hauler.

 

Trade it in for an F150!