2000 GMC Jimmy Heating issues

We have a 2000 GMC Jimmy that we have been having heating issues with. The heater core went out and we replaced that ourselves. But we still have no heat. Heats up to about 180-190 and every once in a while it will get to 210. We just replaced th thermastat the other day and not sure what else to do. Running out of options. If anyone has any suggestions I would greatly appreciate it. :shakehead

We have a 2000 GMC Jimmy that we have been having heating issues with. The heater core went out and we replaced that ourselves. But we still have no heat. Heats up to about 180-190 and every once in a while it will get to 210. We just replaced th thermastat the other day and not sure what else to do. Running out of options. If anyone has any suggestions I would greatly appreciate it. :shakehead

Engine running tempt should be 195 degrees.
180 will not produce good hot heat.

How often and where and how does it jump up to 210?
Does the tempt jump up fast on a long hard pull on road?

When engine is up to operating tempt around 195 feel both heater hoses and see if they are hot to touch.
Let us know how both feel.

Do you have regular or auto ma tic AC/heater controls?

Lot of vacuum and electric stuff on AC /heater controls.
Got good engine vacuum to heater controls?

Does all vent and floor and defrost air switch good?
Good cold to hot temp switching.
Good fan on low and high settings?
Ac working good?

Can you feel or hear heater switch from cold to hot tempt setting?

Is coolant tank and rad staying full?

It gets up to 210 every once in a while as you are driving it. Daughter uses vehicle to go back and forth to work and to school. It climbs to 210 slowly. It does not rise fast. The hoses going to the heater core are hot. The one going in is a little hotter than one coming out. Heaterand a/c contros are regular. Air is working fine and so are all vents. Everything switches well. Coolant is always full. We are not losing any fluids. I am not sure if vacuum to heater is good. I am not sure how to check that. We did have air in the system and last night we jacked up the passenger side and finally got the air out. Heat is slightly warm but does not stay warm for more than a half a day.

It gets up to 210 every once in a while as you are driving it. Daughter uses vehicle to go back and forth to work and to school. It climbs to 210 slowly. It does not rise fast. The hoses going to the heater core are hot. The one going in is a little hotter than one coming out. Heaterand a/c contros are regular. Air is working fine and so are all vents. Everything switches well. Coolant is always full. We are not losing any fluids. I am not sure if vacuum to heater is good. I am not sure how to check that. We did have air in the system and last night we jacked up the passenger side and finally got the air out. Heat is slightly warm but does not stay warm for more than a half a day.

You may still have a air lock.
Pull heater hoss and see if you can bleed out air there and check coolant flow out of hoses.
Are you keeping rad and coolant tank full of coolant.

Heater hose should be close to engine running tempt /Hot to the tounch.

Inlet hose should be hot to touch with a cooler out let hose if heater core is working good and has good flow.

It gets up to 210 every once in a while as you are driving it. Daughter uses vehicle to go back and forth to work and to school. It climbs to 210 slowly. It does not rise fast. The hoses going to the heater core are hot. The one going in is a little hotter than one coming out. Heaterand a/c contros are regular. Air is working fine and so are all vents. Everything switches well. Coolant is always full. We are not losing any fluids. I am not sure if vacuum to heater is good. I am not sure how to check that. We did have air in the system and last night we jacked up the passenger side and finally got the air out. Heat is slightly warm but does not stay warm for more than a half a day.

Going to 210 while driving is not normal.
You are losing water pump circulation or rad cooling or stat is bad or a head gasket leakage or air lock or just low on coolant.
Does it raise up to 210 faster on a hard pull?

I have a 2000 gmc Sierra with heating issues also. I've had the heater core flushed $40. I had heat for about a week. Then had the entire coolant system flushed $80. Still no heat. I pull over and check the hoses temperature. Hot going into heater core and cool coming out. I manually pump the upper radiator hose many times and then I have super hot air for the rest of the day. Can radiator hoses fail internally? Can the water pump fail internally? Is an air lock possible if so how? My engine hasn't overheated it runs right around 210 on the gauge.

We have a 2000 GMC Jimmy that we have been having heating issues with. The heater core went out and we replaced that ourselves. But we still have no heat. Heats up to about 180-190 and every once in a while it will get to 210. We just replaced th thermastat the other day and not sure what else to do. Running out of options. If anyone has any suggestions I would greatly appreciate it. :shakehead

have you taken off rad cap off when it cools down and look to see if it's circulating?

I have a 2000 gmc Sierra with heating issues also. I've had the heater core flushed $40. I had heat for about a week. Then had the entire coolant system flushed $80. Still no heat. I pull over and check the hoses temperature. Hot going into heater core and cool coming out. I manually pump the upper radiator hose many times and then I have super hot air for the rest of the day. Can radiator hoses fail internally? Can the water pump fail internally? Is an air lock possible if so how? My engine hasn't overheated it runs right around 210 on the gauge.


Radiator very seldom fail but I have saw lower hose suck closed on some older systems on warm up.
In rare cases heater hose couplers and or restrictions can clog up.
Make sure your rad and coolant tank are staying full.

How are You manuually pumping?
Does it lose heat when restarted of moring untill you pump hoses and the work good all day?
Or heat some untill it warms up and then fade out?
Your heater core may still be partly clogged/stopped up.
I would bleeding heater hoses and try reversing heater hoses to heater core.
Also stick return hose from heater core int coolant tank and look for good circulation from heater core.
Was any coolant system cleaner/flush used when system flushed?