running too hot!

I have a 99 with a 5.3 and the water temp is getting way to hot. I noticed it a couple days ago when it was about 78* out. I had the ac on and i drove it for about 15 min then pulled into a buddys drive way and let it sit running for about 10 min. when i got in the truck the temp was at 240*! So today i put a 160* stat in it and a bottle of water wetter in it. and its still the same.

I alos noticed that my clutch fan has been super loud. Even after the truck as cooled of some what, it is still loud.

Any help would be great. Thanks

When was the last time the front of your radiator was cleaned? Perhaps there is no air getting through the Radiator itself??? Or perhaps it's clogged somewhere in your HVAC System inside the truck. 2 things I hate fixing on trucks.
Water probs and Electrical....happy hunting let us know what you find out. Your Engine fan should be loud as it's trying to cool your super hot engine...

If i were you i would ckeck that your water pump hasnt sheared the shaft. My truck doesnt have a radiator cap so if thats what your have i am not sure how you will ckeck flow rates, and if you engine did actually reach 240 then things are only going to get worse from now on. probably cooked some vital seals and your rings and cylinders probably will need some work soon.240 spells death usually...jj

would not run any cooler thermostat than a 180 degree.

If you truck is still doing this (and I imagine it is) don't drive it unitl you get it fixed. First is the airway clear and the radiar in decent shape? No rust or crap in the radiator? If so then Lookt to your water pump and or radiator fan clutch. If the fan clutch has never been repalced it could certainly be a problem.

I looked and there is no crap blocking the radiatior. I also only gets hot if it sits. When i driving it its fine. I not sure how hot it actually got but the needle was between the 210 and 260 mark on the gauge. How do i know if the clutch on the fan is bad and how do i tell if the water pump is going?? I just dont want to change the pump and that not be the problem because im sure it not cheap.

Yea, I had an old blazer that got about that hot a time or two. Two weeks later, both of the plastic side pieces on the radiator cracked in two. I could have replaced them, but to buy them both was more than a whole new radiator. I was having problems with cooling before that and the new radiator took care of it so it was probably all stopped up. My dad's truck did the same thing, I think it was a 95.

water pumps are not that expensive. You can get a decent one at Napa or other places for between $50 and $100. They are not to hard to change yourself if you have some experience with that. Basically a waterpump usually is considered good if its not leaking at the "weep" hole, small hole on the bottom of the water pump the leaks when the bearing fails, or you notice that the flow through the radiator is not adaquate. The flow question is a judgement calll... the leak part is something you can check.

On the fan clutch (first I would only buy a GM fan clutch) you can get good deals here (rockauto.com). Rotate the fan by hand (engine off ...of course) and see if you can tell if there is any "bearing slack" or wobble to the shaft when you turn it.... 2nd crank truck up and let it get not an warm...go drive it around a while...come back and stop and turn engine off. Right then open hood and turn fan by hand....it should be hard to turn by hand with truck hot. If it free-wheels or you notice "slop" in the play when the engine is hot you should replace the fan clutch. I've never seen any aftermarket fan clutchs that I thought were worth buying...one of the few things that you really should purchase from GM.

One thing to check in general is the area between your A/C condensor and your radiator. You can't really see this without removing the top half of the radiator shroud and tilting the radiator backwards a little. Take your water hose and clean this area out good.

I would think that if you find no leaks....and you don't have any issues with the radiator or the air-way across the radiator, then most likely its the fan clutch. You can get those at rockauto too... Easy to change. remove top half of radiator shroud... remove 4 nuts that hold fan clutch to water pump and you have the fan clutch assembly off. Then take the 4 bolts off that hold the fan to the clutch. Reverse order with new fan clutch.

I just noticed you said you had a 99 truck with the 5.3.... I'm not sure but that truck may have the new style fan clutch that has the large single nut that connects it to the water pump...if so then thats going to make the swap out a little different in that you need a wrench to fit that large nut. Take a look under the hood before you get started to see what style fan clutch you have.

I have no connection to Rockauto... I've just found that their web site has an easy to use tool to locate parts, they offer good prices, and they process your oder in a timely fashion. I've grown tired of getting reamed at the local GM shop for parts.

Ok well i just put the new clutch for the fan on. The temp seems to be ok but i havnt drove it alot yet. But the fan i super loud all the time. Is that right?? I have only owned this truck since october and i hava never heard the fan sound like this nor has it ever had any cooling problems untill this past week.

no the fan should not be loud all the time. On a truck / car , rear wheel drive with a clutch fan.... the fan only engages when the vehicle get to a "Certain" temperature...thats when you hear the load roaring noise because the fan clutch is engaged and its pulling air through your radiator at a larger volume.

You don't have a piece of cardboard or something blocking the radiator? The fan clutch should not stay engaged all the time.

So you put new fan clutch on and loud noise still the same? Soemthing is not right! YOu need to carry it to a shop and let them check it out. I can't see the truck from "here", but I can tell you that this does not sound right.
I would not drive it until you get it checked. They way you describe it...it sure sounds as if the radiator is either partially blocked or something is wrong with the radiator internally. Play it safe get it checked.

If you can borrow a scan tool you can tell exactly how hot its getting. I know on the OEM guages its a little bit if guessing.

Bottom line the fan clutch should not be engagind all the time.

Now when its really hot you will hear the fan clutch engage, especially in stop and go traffic, slow speeds, and right off when you start after ideling for a while... 90degrees or so outside, it will do this. THe fan clutch engages on the highway sometimes...like climbing a long grade normally. Most times on the road you don't notice it. Will also do this if you are towing something heavy.

You checked the inside of the radiator for sludge and or good flow once the thermostat comes on? Don't open the radiator cap when the truck is hot!...but you can open it cold and then let truck run for a while to see what the coolant is doing in the radiator. Truck never had problem until now?

A lot of this stuff requires some experience to know what is right and whats not... I would drop it off at your local shop and tell them what its been doing.
Let us know what "they" say...

Ya i never had a problem untill now but like i said i only go the truck in october so it was never that hot out. The radiatior has no cap on it, i have to fill it from the over low tank so i cant check the flow. Also i had the shroud off and i looked at the radiatior and there was nothing blocking it and in between the radiatior and the condesor was nothing.

and yes the fan is ingauged all the time. It doesnt run hot but it is extremely anoying because its very loud.

It kinda weird

are you saying the radiator has no cap as part of the radiator??? in other words the radiator in your truck has no place for a radiator cap?

IF that true...someone has swapped in some odd-ball radiator in your truck?
You need to find out what kind of setup someone has done on your truck. Find a friend or someone who has a similar truck and compare yours to theirs.... I would contact the former owner to see what is going on.

Like I said...you need to carry it to a shop that works on this stuff to see what the problem is.

The fan clutch should not stay engaged all the time, and every pickup I've ever seen has a radiator cap.... you might have some big air pockets in your cooling system. Do yourself a favor and let someone look at the truck who knows what they are doing, so they can give you some advice.

It is a stock radiatior. Its a new style silverado. You fill the coolant through the overflow. None of the newer ones have a radiatior cap they all fill through the overflow.

The cap on the overflow tank is still pressure activated. It just sits in a non standard location....... Also by putting the overflow tank higher it keeps air out of the radiator and just in the overflow tank if everything isd running properly.

Sulblime have you checked the fluid level when the truck is running? Don't rely on the stains on the plastic either. Be careful and open the cap when running to see if the fluid level is up to the middle of the tank.

My fan is staying on more than normal, but my temp does not waver from the normal temp it has always run at. It's definitely not on all the time, though. I did the test from the post above, and after running, it's just as easy to move as when cold. Not really free-wheeling, it doesn't continue to spin after I remove my hand (hot or cold), but it is not at all harder to move when hot.