Please help!!

[bill1013]

My 1999 Tahoe water temp was always 210 degrees...at least that was what the gauge read. Isn't 230 a little high for the engine to run at that temp? It sounds like your circulating steam, not coolant. And are you using Dexcon, orange, coolant. Just water isn't good for the engine cooling system and leads to overheating. It's okay in a pinch, but as soon as you are able you should flush it and replace it with the proper coolant. And I know this sounds really stupid to bring up, but sometimes we tend to overlook the simplest things that often lead to disaster. Just a thought...

 

[Doubeleive]

My 1999 Tahoe water temp was always 210 degrees...at least that was what the gauge read. Isn't 230 a little high for the engine to run at that temp? It sounds like your circulating steam, not coolant. And are you using Dexcon, orange, coolant. Just water isn't good for the engine cooling system and leads to overheating. It's okay in a pinch, but as soon as you are able you should flush it and replace it with the proper coolant. And I know this sounds really stupid to bring up, but sometimes we tend to overlook the simplest things that often lead to disaster. Just a thought...

it seems like he just has a clogged radiator, it could have been the issue all along

 

[mike_whip]

My 1999 Tahoe water temp was always 210 degrees...at least that was what the gauge read. Isn't 230 a little high for the engine to run at that temp? It sounds like your circulating steam, not coolant. And are you using Dexcon, orange, coolant. Just water isn't good for the engine cooling system and leads to overheating. It's okay in a pinch, but as soon as you are able you should flush it and replace it with the proper coolant. And I know this sounds really stupid to bring up, but sometimes we tend to overlook the simplest things that often lead to disaster. Just a thought...

It always has been running at 210 up until recently. Even after doing the head gaskets it was running at 210 for a little while until it started acting up again.

Ya, I am using the Dexcon orange coolant for GM. I get the 50/50 blend so it is ready to pour right away.

 

[mike_whip]

it seems like he just has a clogged radiator, it could have been the issue all along

Sure could be! I am going to be looking into that too. If it was you, would you replace the stock radiator with that many miles on it or would you just flush it?

 

[Doubeleive]

Sure could be! I am going to be looking into that too. If it was you, would you replace the stock radiator with that many miles on it or would you just flush it?

well 1st thing I would do is pull both hoses off the radiator and stick a hose in the upper hole and put a water hose in it and see how the flow out is, just to confirm if it is clogged or not it should have pretty good flow, all that aside my rule of thumb is 5 years on a radiator unless it has been flushed annually and is in real good shape.
living in CA where it gets hot my experience has been after a radiator is a few years old they will not cool as well and something as simple as sitting at a red light in the summer will make the temp go up some and then return to normal while moving that is a sign it needs to be replaced OR the fan clutch (if equipped) may not be working properly, electric fans usually work pretty well for many years, if they are making noises at startup or when running at low speed that is a indication of motor wear but usually heating issue's like I described is the radiator is no longer efficient as it was when new.

 

[mike_whip]

well 1st thing I would do is pull both hoses off the radiator and stick a hose in the upper hole and put a water hose in it and see how the flow out is, just confirm if it is clogged or not it should have pretty good flow, all that aside my rule of thumb is 5 years on a radiator unless it has been flushed annually and is in real good shape.

Thank you for the advice. Going forward, I will use that.

 

[bill1013]

One way to check to see if the water pump is functioning is to take the cap off and start it up. You should see the coolant moving inside or even the coolant coming out from the core. Another way is to squeeze the hose to see if they are firm. I believe the lower one should be pretty hard to squeeze if the pump is functioning as the top, the one that feeds the cores should be relatively soft or flexible. Also there's a reservoir on the passenger side firewall that is supposed to be where you service or add coolant. It sucks, or empties when it gets hot and the coolant return as the engine cools. I had the hose and cap come off once and it created problems. It sucked air instead of coolant and when it cooled it spewed coolant on that side of the engine compartment. So you might want to check that hose, at both ends, and the cap. Hope that helps.

 

[bill1013]

Also, if your radiator is plastic the top it may have a crack in it. The radiator leaks from the crack, which is on the top of the radiator, only when the engine is running. So you won't see it statically. Mine had that and that's when I saw that the core is aluminum, but the sides are plastic...and they tend to crack over time. And when I priced an all aluminum of metal radiator it was $850. To put in the same one as I was replacing $135. I would have gone with the metal one but it would have taken two weeks to ship it out here, so I went with the $135 model as my Tahoe was my work everyday truck. Wouldn't leave home without it. Now I'm loving my Yukon as much as the Tahoe.

 

[mike_whip]

One way to check to see if the water pump is functioning is to take the cap off and start it up. You should see the coolant moving inside or even the coolant coming out from the core. Another way is to squeeze the hose to see if they are firm. I believe the lower one should be pretty hard to squeeze if the pump is functioning as the top, the one that feeds the cores should be relatively soft or flexible. Also there's a reservoir on the passenger side firewall that is supposed to be where you service or add coolant. It sucks, or empties when it gets hot and the coolant return as the engine cools. I had the hose and cap come off once and it created problems. It sucked air instead of coolant and when it cooled it spewed coolant on that side of the engine compartment. So you might want to check that hose, at both ends, and the cap. Hope that helps.

Yep, we have done that and that is how I also filled up the coolant. I had the cap off, the funnel on, the Tahoe running and emptying in the coolant into it. It would burp out the air while going into the vehicle so I know it has to be circulating somewhere. I am going to flush the radiator and the heater core first and then move on to replacement of the radiator.

 

[SnowDrifter]

ya I meant temperature sensor, seems like someone reported a overheat issue before because of the restrictor not being in place I was under the assumption that it could go either way depending on how much return was flowing back in, or maybe the hoses were on wrong or something.

The whole reason why they'll run cool without that restrictor, is that these engines run a 'reverse' thermostat. Instead of the tstat being on the output side of the water pump, it's on the inlet. Which means that the radiator is pressurized by the water pump the second the engine is turned on.

There's a bleed-tube on the top-pass side of the radiator that returns to the overflow tank. The end result being, there's always a little bit of coolant going through the radiator. Usually this is a net benefit - the system self bleeds, and does so very quickly. However if that restrictor is not in place, there will be more than a little coolant going through the radiator, wicking away more heat than was intended in the design. So no restrictor = too much flow through the self-bleed = too much flow through the radiator = cold

Now with that said... These systems are flippin' weird in that it uses the heater core lines to control the thermostat. So if your heater cores are clogged, or if you did a lazy bypass and just capped hoses - there won't be enough coolant going over the t-stat to appropriately regulate temperatures, and you'll get an overheat / hot condition even if everything else in the system works perfectly. This also goes for a partial clog. So if, for whatever reason, you wanted to bypass your heater core - you would loop a piece of hose around and just connect the waterpump to itself, NOT cap it off.

Thank you @SnowDrifter, I appreciate the tips. I did not fil it from the upper radiator hose but I can definitely try that.

I replaced the fan relays just in case the fans were not kicking on at the right time. They were $11 and a cheap fix if that could have been the issue. The fans do not come on until 230-235 degrees but seem to make no difference as the temp keeps on climbing.

I did not take the hose off of the water pump and spin it, I will get on that over the weekend or in the evenings if I have time this week.

Interior heat blows cold even at operating temp until I give it gas in idle or take it for a spin, and then it gets hot. However, if I don't step on the gas, the heat stops and the cool air comes back in.

Couple bits come to mind, in no particular order

1. If you get heat when revved, the water pump is spinning. It's not air locked.

2. Double check coolant level in your reservoir. Low coolant is the first thing I'd be looking at here. Especially if you get any gurgling / waterfall type sounds from under the dash.

3. Verify your belt isn't slipping. From a cold start - let it run for a minute or two. Turn the engine off. Then go ***** the pulleys. Are any of them warm/hot?

4. How's that water pump looking anyway? I've seen some realllll bad aftermarkets. Some have a raw pump with no vane guide. Those are lame. My favorite was one that didn't even have an impeller on it... oops....

5. You can try back flushing your heater core. Disconnect the hoses and put a garden hose on it. The port on the rear of the engine is the outlet to the heater, front is the inlet to the pump