Overheating Issues, Wierd, Ideas Needed

[myakka]

My 2004 Yukon SLT (5.3) started to overheat slightly last week. Checked the coolant and sure enough it was low. A few days later, the same thing, low coolant. The gauge never got above 3/4.

 

I checked it out closer to find the leak and sure enough it was coming from the water pump. No problem, replaced the water pump and thermostat (took about 2 hours). When I removed the old pump i removed the water pump to block gaskets, and cleaned the surfaces. The thermostat is in correctly.

 

I followed the GM instructions on burping the system, several times. I even replaced the thermostat again to make sure it was not the culprit. I also tried disconnecting the upper radiator hose and pouring coolant in that way to rule out an air lock. Yes the pump is spinning, so is the fan.

 

Here are the current symptoms.

 

1.) Truck starts, and after 2 minutes or more the temp gets up to 190-200F. Once this point is reached the temp ratchets up a little every 10-15 seconds.

 

2.) At this time only a little heat can be felt if the heater is turned on. Previous to the water pump change the heater worked fine.

 

3.) Even when the temp is at 200 the lower radiator hose feels "warm", not hot.

 

So the only things I can think of are (please correct and feel free to lend advice):

 

1.) The water pump to block gaskets moved somehow and are restricting coolant flow

2.) The heater core lines are backwards (I am guessing at this one)

3.) Monster air lock

 

Any and all help is greatly appreciated

 

 

 

 

 

 

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[Zembonez]

If the gasket on the water pump had shifted, you'd have an obvious leak.

 

Heater core hoses are not going to cause an overheating issue.

 

Sounds like it might be air in the system. I know when my 01 had air in it, you could hear it gurgle in the heater core when I accelerated.

[myakka]

Thank you for the reply. If it is air in the system, why is it being so stubborn?

 

I have parked it uphill, downhill, even drove it in circles for a minute. After this it did take another 1/2 gallon of coolant but no noticeable improvement. Is there a trick with the 5.3 to make it burp and get all the air out after a water pump change? I miss the days of having a radiator cap

[Zembonez]

I actually refilled mine through a heater hose with the reservoir cap off until it was full. Maybe somebody will chime in here that has more experience with this.

[myakka]

Thanks again, I am wondering if flushing it will help get the air out. Hopefully someone has experienced something similar i and knows more tricks.

[txab]

As for heater hose configuration, the passenger side heater core hose (hose has a wye that goes to the plastic reservoir) goes to the front connection on the water pump. I've filled through the upper rad. hose with no problems as well as doing it Jim's way. I never had a problem getting all the air out

 

 

Here's a method of purging that is located in tech wiki.

 

http://www.gm-trucks.com/forums/index.php?...icle&id=394

[myakka]

As for heater hose configuration, the passenger side heater core hose (hose has a wye that goes to the plastic reservoir) goes to the front connection on the water pump.

 

Thanks! From memory since I am at my desk: On the yukon both heater hoses terminate at the water pump. The hose that goes to the plastic reservoiris twice as thick and looks to Y with the upper radiator hose?

 

Edit: Are there bleeder screws on this motor? I can't find a service manual.

[txab]

Both heater core hoses do connect to the water pump. Passenger side HC hose goes to the front fitting. The drivers side connects to the rear fitting. The passenger side HC hoses is joined with the reservoir tank hose (Y). The upper radiator is only connected to the top of the water pump and radiator.

I would flush the heater core while having this opportunity.

 

Have all your hoses been replaced before now? If not, now would be a good time. A 6 or 7 year old hose might give you trouble someday and since your putting a fresh load of Dex coolant in it, why waste it by having to drain it again when you have a hose go bad in the near future possibly.

[myakka]

Thanks again. So I should probably just use one of those inline coolant flush kits? yes all hoses are in good shape or have been replaced.

 

I keep seeing posts about people drilling holes in thermostats. This doesn't seem needed since they come with little holes already?

 

Both heater core hoses do connect to the water pump. Passenger side HC hose goes to the front fitting. The drivers side connects to the rear fitting. The passenger side HC hoses is joined with the reservoir tank hose (Y). The upper radiator is only connected to the top of the water pump and radiator. There are no bleeder screws.

 

I would flush the heater core while having this opportunity.

 

Have all your hoses been replaced before now? If not, now would be a good time. A 6 or 7 year old hose might give you trouble someday and since your putting a fresh load of Dex coolant in it, why waste it by having to drain it again when you have a hose go bad in the near future possibly.

[txab]

I just flush with plain water the heater core when the hoses are loose from the water pump, it's a great time to do so. It's just to make sure everything is free flowing.

 

If your hoses are properly connected already I'd skip the heater core flush at this point, since I believe you said it was working well before.

 

Yeah your 'stat should have the bleed hole in it already

[ken1mod]

sounds like a bad gauge. get one of those ir hand held laser thermometers that you point at . check temps around the engine and the upper rad hose. those thermometers are fun and useful

 

ken

[myakka]

sounds like a bad gauge. get one of those ir hand held laser thermometers that you point at . check temps around the engine and the upper rad hose. those thermometers are fun and useful

 

ken

 

Turned out to be air in the system. I did the following:

 

1.) Pulled the upper hose off and filled

2.) Filled to cold level via overflow

3.) Started and loosened the upper hose to bleed any air our

4.) let warm up 2 minutes then loosely placed cap on overflow

5.) cycled between idle and 3000 rpm at 30 second intervals

* Noted that the overflow bubbled profusely when letting off the gas

6.) Tightened cap and ran a bit longer

7.) Let cool and added a little to the proper fill line

 

All is better now, what a pain. Made me miss my 66 mustang and it's simple cooling system. Thanks everyone.

[AGT]

I had an Air lock once and found a simple solution. Parked and ran it with the cap off the coolant for a little while. bubbles formed and next thing you know I had heat again and not leaking anymore. I couldn't believe it.