1995 gmc k1500 4wd does not heat replaced thermostat but still no heat

10

Asked by Nov 30, 2013 at 12:15 AM about the GMC Sierra 1500

Question type: Maintenance & Repair

And now temperature gauge keeps going from like 150 to like 260 like to over heat the it goes back down again then eventually climbs back up to overheat again then drops back down and keeps doing that. One heater hose is Luke warm and one cold when the temp. Gauge is at 210. Please help. Thank you.

5 Answers

Thinking water pump. The vanes, often plastic, will wear shorter and sounds like the pump is working but at a greatly reduced capacity. The lukewarm one will be the core feed, and it sounds like it's flowing because the other does come out cold, just not enough flow.....bringing us back to pump issue.

3 of 3 people found this helpful.
109,985

After replacing the thermostat did you get all the air out of the cooling system? An air pocket in cooling system can also cause the gauge to jump around and also lead to no heat when heater is turned on. Just a thought.

3 of 3 people found this helpful.
10

Thank you, that's what I was thinking. Cause where the bypass line coming off of the heater core that runs to the pump, where it goes into pump the has been some leakage on the connector. How can I test the water pump?

1 of 1 people found this helpful.
10,045

I'm with Dandyoun. You are air locked for sure. And it sounds like the coolant level is dangerously low in the engine. Don't run it until you fix it. (FYI: 20% of all new thermostats that I by are not 100% functional. They are cheap I always buy extra and test them in water before I install them. I've cooked 1 good motor through over heating so leason learned. My procedure: 1.) Inspect, there should be no light visible through the sealing surfaces. 2.) Place the thermostat on a level suface and ensure the seal holds water. 3.) Put it in a pot and warm water until it opens (you can verify temp too). 4.) pull it out and watch it close. 5.) It should close completely, if it sticks or does not close throw it away, it's not worth damaging your motor. ) On any motor you should ensure that the engine is full of coolant up to the thermosatat, even if there is a bleed valve, before installing the thermostat. With your motor the heater hose should leave the engine block and circulate through the core back to the rad (The warm hose is probably being heated from the engine and the air lock not fluid). You should be able to fill your rad (not the external reservoir) and run your engine for short periods of time to break the air lock and re fill the motor with coolant. Keep checking the level IN THE RAD every time you shut it off and top it up until it remains full. Once full and the level doesn't drop, put the rad cap back on and run the engine up to operating temp, the thermostat should open and purge the remaining air out of the block. Let the rad cool, open the cap and top it up. Now that most of the air is out the system should operate correctly and draw additional fluid from the reservoir as needed. NOTE: If the second hose returns back to the motor, not the rad you will have to bleed the air out of the top of the motor either by pulling a heater hose off or pulling the thermostat back out.

3 of 3 people found this helpful.
10,045

Was writing that long reply while you posted your reply to the other comments. Check the coolant level in the rad first before you look at the pump. It cannot pump if there is no fluid. The return from the heater will be the line entering the water pump and the hot supply should be towards the back of the block. The water pump pushes fluid into the block forcing the coolant out of the top to the rad or the back to the heater, then back to the suction side of the pump. If the engine is air locked there will be no fluid circulating through the heater hoses.

4 of 4 people found this helpful.

Your Answer

Add photo

Related Questions

  • No heat 2 answers

    Hvac works, but no heat is generated. Any thoughts?

    1999 GMC Sierra 1500 SLT 4WD Extended Cab SB

    -

    Maintenance & Repair

  • No heat any ideas? 7 answers

    Ive got a 95 gmc 1500. I recently replaced the heater core along with the hose from the core to the water pump and hose assembly to the block. I have no heat and my fan will blow light at time th...

    1995 GMC Sierra 1500

    -

    Maintenance & Repair

  • Will not move in Drive or Reverse 14 answers

    1995 GMC Sierra k1500, 350, 5.7 Automatic : Take it out of park, into drive or reverse, step on gas, rpm's fly, but won't move an inch. Have not driven in a week or so, had to replace radiator becaus...

    1995 GMC Sierra 1500 K1500 SLE 4WD Extended Cab SB

    -

    Maintenance & Repair

  • I have a 1993 GMC Sierra just replaced water pump thermostat and radiator and I still have no heater inside the truck 6 answers

    Before I changed water pump out my heater would work off and on then it quit altogether so I change water pump out but I'm still not getting any heat in my truck I check the heater door inside the...

    1993 GMC Sierra 1500 K1500 4WD Extended Cab SB

    -

    Maintenance & Repair

  • why is my gmc suburban temp gauge fluctuating 10 answers

    a few days ago my temp gauge started to fluctuate and at times goes in the red zone and the check gauges light comes on and i get no heat, then it goes back down and i get heat. at times it stays stea...

    1996 GMC Suburban K1500 4WD

    -

    Maintenance & Repair

Sierra 1500

Looking for a Used Sierra 1500 in your area?

CarGurus has 68,199 nationwide Sierra 1500 listings starting at $2,484.

ZIP:

Search GMC Sierra 1500 Questions

GMC Sierra 1500 Experts

#1 dragonflyoffshore
dragonflyoffshore
Reputation 5,010
#2 John Saffrahn
John Saffrahn
Reputation 3,540
#3 Glenn Clingenpeel
Glenn Clingenpeel
Reputation 3,150
View All

Related Models For Sale

Used Chevrolet Silverado 1500
1,717 Great Deals out of 175,751 listings starting at $1,250
Used Ford F-150
2,194 Great Deals out of 206,316 listings starting at $1,499
Used GMC Sierra 2500HD
111 Great Deals out of 14,005 listings starting at $2,650
Used Toyota Tundra
441 Great Deals out of 34,312 listings starting at $2,700
Used Dodge Ram 1500
455 Great Deals out of 11,152 listings starting at $700
Used Ram 1500
924 Great Deals out of 113,958 listings starting at $6,386
Used Toyota Tacoma
539 Great Deals out of 40,814 listings starting at $2,495
Used GMC Yukon
376 Great Deals out of 18,226 listings starting at $2,950
Used Chevrolet Silverado 2500HD
307 Great Deals out of 27,740 listings starting at $1,250
Used Chevrolet Tahoe
547 Great Deals out of 29,234 listings starting at $1,699
Used Ford F-250 Super Duty
346 Great Deals out of 46,938 listings starting at $1,895
Used GMC Canyon
92 Great Deals out of 9,387 listings starting at $2,495
Used Chevrolet Camaro
226 Great Deals out of 30,943 listings starting at $1,217
Used Chevrolet Colorado
214 Great Deals out of 24,313 listings starting at $2,495
Used GMC Sierra 1500HD
7 Great Deals out of 115 listings starting at $2,995

Content submitted by Users is not endorsed by CarGurus, does not express the opinions of CarGurus, and should not be considered reviewed, screened, or approved by CarGurus. Please refer to CarGurus Terms of Use.