Coolant problem.

[Patriot17763]

i have a few ideas what it might be but I want some advice before I start digging in...

My Tahoe has Intermittent heat, and it’s usually only as long as I have it up around 1500-2000 rpm. It also is using coolant. It has never started to over heat until a few nights ago. I didn’t let it get hot it got a few marks above where it normally sits and I shut her down. The oil smells fine. I just changed it and it doesn’t have any milk look to it and it doesn’t smell any different then normal. Please help. I got a few days off work and need to fix this. There is no real coolant smell and no visible leaks... I’m thinking it’s going somewhere and out the exhaust...

 

[Patriot17763]

I am thinking it’s either an intake manifold leak on the exhaust side or a heater core?


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[Doubeleive]

have you crawled underneath with a flashlight and looked around under radiator, bottom pulley, bottom of engine area?
if it is overheating then it is low on coolant (indicating a leak or engine problem)/thermostat stuck closed/bad water pump one of those 3 or the engine needs work.

 

[Patriot17763]

There isn’t leaks so I may just do the water pump and thermostat to start since it probably needs done anyways


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[Patriot17763]

I just filled it up cold, started it and it sucked up about a quart and now stuck around 180 and once i started driving bounced up to normal temp


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[Fless]

@Patriot17763, it could be air in the cooling system; if you haven't already done this you could make sure it's been purged. Might be worth a try before replacing parts. From the Haynes book:

Refilling
12 To refill the system, install the thermostat and reconnect any radiator hoses.

13 Place the heater temperature control in the maximum heat position.

14 Be sure to use the proper coolant listed in this Chapter's Specifications. Slowly fill the surge tank with the recommended mixture of antifreeze and water to the FILL COLD mark.

15 With the surge tank cap off, start the engine and let it idle for about a minute.

16 Install the cap on the surge tank, but don't tighten it down (pressure must be able to escape). Raise the engine speed to approximately 3000 rpm in 30-second cycles until the engine reaches normal operating temperature and the thermostat opens.

17Turn the engine off and remove the surge tank cap. If there is any hissing noise coming from the tank, wait until it stops then remove the cap.

18 Start the engine and let it idle for one minute. Add coolant to the tank until the level is 1/2-inch above the FILL COLD mark, repeat Step 16, then turn the engine off.

19 Add coolant as necessary to bring the level to 1/2-inch above the FILL COLD mark on the tank. Install the surge tank cap securely.

20 Check the cooling system for leaks.

 

[Doubeleive]

keep an eye on it a quart isn't a enough to make it run hot especially this time of year

 

[bottomline2000]

Sounds like a bad water pump. The impellers will break down and start to flow less coolant than normal..
Usually revving the motor will bring the engine temp back down. Check for leaks at the bottom of the water pump,. There is a weep hole there that's a known source for leaks.

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