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Question about 1998 GMC Suburban

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98 suburban runs hot then cools after overheating light comes on.

Engine has less than 5000 miles, new water pump, radiator is just over a year old, and new thermostat. New engine ran about 50 degrees hotter than the old one. Had the radiator flushed and refilled professionally. Recently had to replace freeze plug on the side of the block. Now the motor heats up until the check gauges light comes on, then cools down within normal operating range. It only does this after it has cooled off for a few hours. After it cools down into normal range it sometimes fluctuates but never gets as hot as it does after it has reached its peak of hot temp the first time. No smell of antifreeze inside or outside of car. no visible leaks either. No white smoke or smoke of any other kind coming from tailpipe, no water coming out of it either. And no coolant is visible in the oil. I recently put bars copper stop leak in it thinking it had a small drip somewhere that wasn't visible. This hasn't seemed to stop the problem either. It doesn't seem to use coolant either. I am by far not a certified mechanic but I do know my way around an engine and can usually fix whatever is wrong with it but I am completely at a loss with this one. Any help would be greatly appreciated as this is the only vehicle I have and is therefore my every day driver.

Posted by thenry77 on

  • thenry77 Jan 16, 2014

    the heat works great. forgot to mention that in my question.

  • thenry77 Jan 16, 2014

    One more thing. The coolant doesn't bubble or blow out of radiator if the cap is removed


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SOURCE: 2000 maxima overheating

You have a new radiator and thermostat, so your coolant was flushed. Was the radiator "burped" afterward to get rid of air bubbles? If not, that needs to be done first - it would explain virtually every symptom you're seeing.

Jack up the car so that the radiator cap is elevated. With the coolant topped off, start the car and let it run until it's about 3/4 of the way to overheating. Then shut it down and go have a beer. When it cools off enough to safely open the radiator cap, do so, and any air trapped in the system will bleed out.

What you're doing is circulating the coolant and the air bubbles inside. The bubbles get lodged behind the thermostat and stay there, keeping it from opening (this causes the car to heat up). When you later pop the cap off the radiator, the pressure is vented from the system, the thermostat opens, and the bubbles pass through. They'll work their way to the radiator (since you've got it elevated) and pop out the open cap opening.

Your coolant level will likely drop somewhat after doing this, as the air bubbles will be gone and the space they took up in the system is now available. You may need to add a little more coolant, so top if off (with the car back on the ground) and recap the radiator, fill the overflow to the marked point on the tank, and you're good to go.

Try this if you haven't already, and post back up with your results. If it doesn't solve the problems, we'll take it further.

Posted on Aug 11, 2008


  • 77 Answers

SOURCE: 1998 Dodge Durango no heat when using heater.


Posted on Jan 08, 2009


  • 69 Answers

SOURCE: Same problem , car has only 86,000 miles

replace that thermostat again...flush radiator any way...then see how it runs...

Posted on Aug 28, 2009


  • 146 Answers

SOURCE: 1992 GMC Suburban over cooled???

You may have been given the wrong thermostat. Either way, you can try a hotter thermostat. If the water pump has never been changed it might be time for a new one. I've already had one that was so old that the propeller inside had the fins rusted completely off and the bearings were so bad it was messing up the timing of the motor. The truck wouldn't idle. And guess where alll the rusted off propeller chunks ended up. . . that's right. In the radiator, heater core and the thermostat. I flushed that truck for three days in both directions to get all that scrap out of there. Good Luck. And if you still have the old thermostat you can always throw that one back in, just to see what happens.

Posted on Feb 25, 2010


  • 50 Answers

SOURCE: 2004 cheverolet impala 3.4L engine

Sounds like you have an air;lock in your cooling system.Try placing a bleeder on the return hose to the heater core ........looks like a small tap

Posted on Aug 18, 2010

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Related Questions:


My 98 suburban is running hot after 5 minutes of driving ,it has a new water pump,.new head gaskets set and radiator .what's wrong

check for an air lock in the cooling system after replacing the water pump. Check that the thermostat was replaced correctly.

I have a 98' Pontiac Grand Am GT. Car over heats in less than 2 miles and ?the heater blows out cold air, how can I fix this

Hi Josh-
I assume that you have the proper mixture and levels of coolant in your radiator and plastic overflow tank. Open your radiator cap (when the engine is cold) to make sure this is the case. If not, fill as directed by your owners manual.
If the cooling system's thermostat is bad, the hot coolant coming from your engine can not circulate to the radiator in front of the car to dissipate this heat and return to the engine colder.
The odd part you describe is that cold air blows out of the heater. If your car is overheating, you should have above average heat, since your car is running hot.
A bad water pump may also prevent coolant from circulating correctly. Usually, a bad pump will show up as a puddle of coolant underneath your car-since the bearing or seals usually wear out on the pump. However, I've seen where the internal blades or impellers of the pump have worn out due to deposits in the coolant due to infrequent replacement.
Hope this helps!

Symptoms bad thermostat

Did you check the water pump? That is what is sounds like.

Coolant light come on which indicates an overheating condition

You can never run water in the system, water will boil. You must have a 50/50 coolant/water.

Have the system flushed, the radiator can become restricted from old coolant, the fins have very small ports for flow and can become blocked leading to less cooling.

No thermostat means full flow, so this should not be running hot.

Usually the only way a water pump goes bad is when they leak, they are a direct drive, and the propeller never wears out unless at some point someone had to high of a coolant mixture.

Get the system flushed to clean it and have it made into a 50/50, can't have mostly water, coolant dissipates the heat.

If flushing does not help, the cheapest first thing is a new radiator, or get a new core for it, that's cheaper.

Car keeps overheating

Assuming the engine is ok, no leaking head gasket or exhaust problem, you need to know if the radiator fan comes on when the engine reaches 225 degrees. It should also come on when you turn the ac on if the ac works.
Its also possible you have air in the cooling system.

Vw beetle running hot and we cannot find a leak

The problem sounds like your radiator its 12 years old clogged with sediment and losing pressure at the cap or
vapor loss right through the aluminum you can't see it .Its a mist at driving speeds not at ideal .
Do a pressure test on the system 14.6 lbs per sq " also check the heater core both in and out hoses should be hot and have good water flow .
The problem isn't your water pump .
Also look at your spark plugs take them out . If they are burn white the vehicle is not getting enough fuel .


My 1990 subaru legacy was running fine-I went to the store less than a mile away and when I got home something was leaking from underneath the car and there was steam coming from under the hood..i don't...

Just because it was not hot to the touch, does not mean it is not a coolant loss problem----if the coolant is so low, there may not be enough to make the radiator hot (though usually the steam in the system will).
...a stuck thermostat can also let the engine overheat while the radiator remains cool (the fluid only circulates within the engine and is stopped from getting to the radiator.
...likewise a hose could have burst below and let the coolant out, over heating the engine, and the steam going out the ruptured/popped off hose; would look underneath..
...when cool, check the level in the radiator (likely empty),
...and less than a mile away, may not have ever heated the radiator, though usually only a mile to heat up the coolant
...of course there is always sabotage
...and water pump failure, (so no water circulated) causing overheating and no radiator heat, and possibly enough pressure to blow off a hose, but usually the radiator cap relief spring would allow pressure to escape (and that steam would heat up the radiator on the way---but if only steam in the radiator, it would cool off quickly after venting, because no more water in the radiator to hold the heat. all depending on climate,temp and further details , symptoms..
hope helps..

2004 dodge ram is over heating, the thermostat and fan clutch have been replaced.Doesn't(over heat) in cool weather,but will in mod. weather if driven over 70mph or hilly terrain due or increase of rpm,and...

Water pumps can stall out, but do you have air trapped in system.
Had you recently had the system "open" to replace hose, thermostat, temp sensor. Some Ford and GM have a bleeder screw on a high point in cooling system to bleed out trapped air.

Check your trans fluid color. Since the trans cooler is built into radiator (automatics)

IF the engine is overheating the trans CAN overheat
IF the trans is overheating the engine CAN overheat

They share the same cooling source and trans fluid gets hotter than oil, but yet it has a wimpy cooler built into radiator. Maybe add trans oil cooler to system.

Also outside temp affects the cool down rate of the radiator, air trying to cool down hot radiator/engine is less effecting than cool air cooling hot radiator/engine
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