1990 silverado 2500 6.0l overheating problem help!

[huntyr]

So I am dumb and I mixed regular green coolant with my dexcool and didn't know gm did Dex cool, so there was a little muk from it and I did a flush and it cleaned and everything was good, few days after my truck started to over heat, I didn't let it get too hot and got a tow home, I did a new thermostate and that didn't do it my coolant is going up and down bad and then going over the reservoir cap while burbing it, and then overheats,told it was reservoir cap, so replaced that. then found water pump wasn't pumping water so replaced that, and coolant still doing the up and down and over heating, my one friend said air pocket mayeb but I keep getting cracked heads or gasket but no oil in coolant and takes a good while for it to get hot. I am very stumped and also go told maybe my radiator but not going to replace that till I know for sure. =/

[Doug_Scott]

There are many causes of engine overheating. By far the most common cause is air lock in the cooling system. An air lock is simply a pocket of air in an area of the cooling system that does not have an inlet and outlet path. Some engines have bleeder fittings to help remove the air. Unfortunately, those engines are normally in Japanese made cars.

 

Removing the air can be done by loosening heater hoses while filling the cooling system with engine not running. Generally you would disconnect the higher of the two heater hoses and then connect it back up once coolant appears at both sides(at the end of the hose, and the open side where the hose connects). You can also idle the engine with rad cap removed, and use the throttle to raise engine speed to about 3k rpm and then release it. This is sometimes referred to as "burping" the system. If there is air in the heater core, you can sometimes tell by feeling the temperature of the heater hoses. They should both be nearly the same temp if the heater is on. Also have the rad cap tested.

 

Keep in mind that with the cap off, the coolant will begin to boil at an earlier point than the temp gauge indicates. Straight water boils at 100 degrees C, adding anti-freeze to achieve a 50-50 mix raises boiling point to about 106 degrees C. This means that your engine will boil over at a very normal operating temp if the rad cap is either not tight, or defective. This also means that if the pressure in the cooling system exceeds the caps rating, the coolant that is pushed into the overflow or reservoir will be boiling violently.

 

Mixing the two different types of coolant is not supposed to be an issue. The "mud" you have in your cooling system is due to Dex-Cool all by itself. Nothing to do with mixing the two different types. You need to have a chemical cooling system flush done to remove all the "mud" from the entire cooling system. Depending on how much is in the engine, that may be the cause of your overheating.

 

In my near 40 years of mechanic experience I do not recall ever replacing a water pump due to it "not pumping". I have also never actually seen a pump that had failed to pump, or ever heard first hand from another mechanic that has seen one or replaced one due to not pumping. The only way it can stop pumping is if the impeller comes off. There is no pressure on the water pump that would cause the impeller to even slip on the shaft, unless the water pump is full of water, and the water freezes. The one time I have seen that, the pump still did not fail, but it did burn the fan belt off due to the water pump frozen solid. Once the water thawed, the pump started turning, and all the "coolant" drained out the 3 core plugs that were pushed out due to the freezing of the pretty much pure water coolant.

 

If the engine is overheating on the highway, take a good look at the inside of the radiator if you can. Look for blockage in the tubes of the radiator core. Also look at the cooling fins on the radiator. They should be not bent in such a way to block air flow through the radiator, and the fins should not be loose. If the fins are loose, it will be pretty obvious normally, and you will be able to push the fins in and out. Loose fins will require a replacement radiator. If your truck has a rad cap on the actual radiator, you will be able to see inside the radiator to check condition of the tubes.

[Jsdirt]

I saw an impeller come off my buddy's '87 Firebird V6 once - was overheating and making a noise I can only describe as ... if you take a toy that has a wheel on it, and spin it faster than it was designed to go, and it suddenly goes out of balance violently & makes that "BZZZZ" sound, which nearly brings the wheel to a stop instantly. Every time he revved it, it made that sound ... and it was coming from the general area of the water pump.

 

Took a gamble and replaced it ... and when I took the back cover off, the impeller was just floating around inside. First and last time I had ever seen that.

[huntyr]

Ok thanks guys gonna take a look at the radiator and do your air trick

[02suburbanZ71]

I saw an impeller come off my buddy's '87 Firebird V6 once - was overheating and making a noise I can only describe as ... if you take a toy that has a wheel on it, and spin it faster than it was designed to go, and it suddenly goes out of balance violently & makes that "BZZZZ" sound, which nearly brings the wheel to a stop instantly. Every time he revved it, it made that sound ... and it was coming from the general area of the water pump.

 

Took a gamble and replaced it ... and when I took the back cover off, the impeller was just floating around inside. First and last time I had ever seen that.

This made me LOL

[Jsdirt]

Me too when I heard that sound. I think I made some wise-ass reference about a matchbox car to my buddy ...

[gmtech4]

Ok thanks guys gonna take a look at the radiator and do your air trick

There is no trick in service information that says to do that , ( sorry Doug), it is just not done , you have to read up on how to bleed YOUR engine from a service information site , this is just not even near rocket science and I can't believe your having this many problems and throwing parts at it IS NOT COOL, !!!

 

Start again by taking it To a real garage

 

Serously .... Dude !!! Lol

[gonzoid]

how come no one asked if he did the transplant,you own a 1990 truck with a 6.0,a lot of opinions what the issue is and its not clear what he is working on.

[02suburbanZ71]

how come no one asked if he did the transplant,you own a 1990 truck with a 6.0,a lot of opinions what the issue is and its not clear what he is working on.

I just figured he did the swap lol

[Doug_Scott]

how come no one asked if he did the transplant,you own a 1990 truck with a 6.0,a lot of opinions what the issue is and its not clear what he is working on.

 

Generally it does not matter when looking at why an engine is overheating. It is a very simple system, that has some pretty common causes to look at first. I stand by the general way to avoid air locks in cooling systems. Mechanics that work in non dealer garages do not have access to brand specific service manuals, so they learn ways that work for them. Concepts are the same regardless of brand. Air locks are a pain the ass to get around. The big trick is that air trapped above the opening has to be helped out. If the cooling systems were actual direct paths, with positive displacement pumps, it would be a lot easier to bleed air out of them.

[gonzoid]

Generally is the key word here.These trucks dont have air lock problems like some cars do.bleeding air out of these is simple

 

I asked if it was a transplant ,which we still dont know.

 

what if its is a transplant and it has cooling fans that are wired wrong and spinning the wrong direction?

 

the more info the better...like if its a swap

[Jsdirt]

I don't remember a 366 in anything back then, so I'd have to say YES to the swap ....

 

I've also never had an issue getting air out of these engines. Usually just squeezing the hoses, and a heat cycle, gets it all out of there.

[Doug_Scott]

Generally is the key word here.These trucks dont have air lock problems like some cars do.bleeding air out of these is simple

 

I asked if it was a transplant ,which we still dont know.

 

what if its is a transplant and it has cooling fans that are wired wrong and spinning the wrong direction?

 

the more info the better...like if its a swap

 

If the fans are wired wrong and spinning in wrong direction, it would only be an issue at the exact mph speed that matches the fans speed. Just like the 5th generation Honda VFR800 fans did. The fan on that bike spun in a direction that pulled air into engine area across the radiator mounted on the side of the fairing. At 10 to 15 mph the air flow coming in the front of the fairing was at approx. same speed as the air being pulled in from the side of the fairing, thus actually stalling airflow across the radiator. Pain in the ass in heavy traffic.

 

More info is always better, but, no need to not post suggestions that most likely will address his issue while waiting for an answer. I would think that if this has been overheating ever since he swapped the engine, that would have been stated in the original question. Air lock issues are more common than not. They generally work themselves out during the first full cycle of engine temp though.

[gonzoid]

OP has listed on his profile 99 2500

 

with that i would say he may have gave false/mistake info,likely not an engine swap.just a 99 3/4 ton 6.0 overheating.More info like how many miles and what may have been done to it most recently would be helpful