NEED HELP truck doesn’t warm up literally - SOLVED

[OR VietVet]

I was responding to the statement in your initial conglomeration of words that the gauge read low. Yes, it could be reading correct, since the heat output is crap as well. Likely, as has been stated by @YukonGTmaster, that the thermostat is stuck open. I personally would never change ANY engine without doing a new thermostat. Also, you should post the brakes problem in the correct section.

Also, put the pipe down before posting.

 

[Jonny_96tahoe]

I was responding to the statement in your initial conglomeration of words that the gauge read low. Yes, it could be reading correct, since the heat output is crap as well. Likely, as has been stated by @YukonGTmaster, that the thermostat is stuck open. I personally would never change ANY engine without doing a new thermostat. Also, you should post the brakes problem in the correct section.

Also, put the pipe down before posting.

I was responding to the statement in your initial conglomeration of words that the gauge read low. Yes, it could be reading correct, since the heat output is crap as well. Likely, as has been stated by @YukonGTmaster, that the thermostat is stuck open. I personally would never change ANY engine without doing a new thermostat. Also, you should post the brakes problem in the correct section.

Also, put the pipe down before posting.

Ahaha thanks man! I’m still a newbie so I’m getting used to this. I’ll go find that section thanks again!

 

[east302]

In your photo below, the blue line is a vacuum and it connects to that solenoid on the firewall. Your red line would go to a plastic valve on the heater lines.



When you select the “Max” detent on the a/c temperature dial, this solenoid is energized and vacuum is applied to close that valve on the heater lines. The intent is to maximize a/c performance by shutting off flow to the heater core.

My 98 is plumbed a bit differently, that blue line connects to my PCV valve fitting on the driver side. Your vacuum line appears to connect to the EVAP purge solenoid. That draws fuel vapor into the intake from the round canister on the driver side - your last photo.

That seems odd to have the water valve solenoid connected to that. I want to say that it would be an open vent on that port but maybe someone with a 96 or 97 could confirm. My 98 has a different style Evap purge valve.

What vehicle did the new engine come out of? Pickups did not use the valve on the heater lines. On my 98 truck, it does not have the port on the PCV fitting while my Tahoe does.

1998 Truck PCV fitting:



1998 Tahoe PCV fitting:



The red arrow points to the vacuum that connects to the water valve solenoid.

It probably doesn’t really matter as neither would account for low coolant temperature, but if the solenoid is constantly energized then it would impact heater performance. Unplug the solenoid in that case to see if it changes. There’s also a spring-loaded plunger on the water valve at the heater lines. It’s the shaft for the butterflies in the valve. If it pushes up and down with the engine running then the valve is open.

As for the dash gauge, most report it running at about this point with the 190 (or is it 195) degree thermostat:



The intermediate tick marks don’t really correspond to any number (the first half of the gauge is a 110 range while the last half is only 50) so it’s just an approximation…similar to how Ford just wrote NORMAL on their gauges and called it a day.

The gauge sender is on the driver side head. The coolant temperature sensor is right by the thermostat. That is what the computer uses. You’d need a scanner to read the value and, if you have one, would be a good thing to know.


Couple questions-

Did you bleed the radiator?

Are the heater lines hot - too hot to hold more than a second or so?

Does the upper radiator hose ever get comparably hot?

 

[Jonny_96tahoe]

Dude!!! Thanks for all the suggestions Motor came out of a 95 I believe Chevy k1500, I believe the old motor that came out of my Tahoe tho had that driver side vacuum thingy the motor now from the k1500 seems to not have it beside the throttle body pictured below & yes made sure no air was in her! & 1 heater line gets barely warm the other gets a decent warmth to it no to hot to touch tho even the upper radiator hose doesn’t get hot hot I can hold it after a 30 min drive :0

 

[east302]

If your replacement engine included the intake, then it looks like a 96 or 97 since you don’t have the throttle body injection. Maybe @YukonGTmaster can let you know if his water valve solenoid is connected to the evap purge or to the PCV. I think he has a 97.

So the heater worked before the swap? If so, that should rule out a blocked heater core. Just for kicks, find the metal plunger on the heater hose water valve and see if it moves up and down. If it’s stuck up or in, then the valve is closed.



Heater hoses are connected correctly?




I’ve heard of people having a clog in the heater inlet hose at the quick connect causing poor heater performance. I’m not sure if it would explain your overall coolant issue, but it may be something to check. Pinch the ears on the plastic retaining clip and pull the hose out.

It will have a plastic orifice inside it restricting it somewhat, but if you pull the hose you can see if the connector in the intake is blocked. Go ahead and buy a new plastic retaining clip for it beforehand, it’s liable to break. Parts store have them, usually available separate from the complete quick connect fitting.







Otherwise, I’d be real tempted to swap that thermostat out.

 

[OR VietVet]

That connection, circled in yellow, can be a SOAB to get open if severely corroded and/or rusted. I have seen them leak where they thread in and then break off during the removal. Thankfully the pipe thread there is very large and if you work at it, you can go down one side of the broken off section and use a sharp small chisel and break out the pieces until it collapses in on itself. The design is crazy stupid.

 

[Jonny_96tahoe]

If your replacement engine included the intake, then it looks like a 96 or 97 since you don’t have the throttle body injection. Maybe @YukonGTmaster can let you know if his water valve solenoid is connected to the evap purge or to the PCV. I think he has a 97.

So the heater worked before the swap? If so, that should rule out a blocked heater core. Just for kicks, find the metal plunger on the heater hose water valve and see if it moves up and down. If it’s stuck up or in, then the valve is closed.

View attachment 383252

I’ve heard of people having a clog in the heater inlet hose at the quick connect causing poor heater performance. I’m not sure if it would explain your overall coolant issue, but it may be something to check. Pinch the ears on the plastic retaining clip and pull the hose out.

It will have a plastic orifice inside it restricting it somewhat, but if you pull the hose you can see if the connector in the intake is blocked. Go ahead and buy a new plastic retaining clip for it beforehand, it’s liable to break. Parts store have them, usually available separate from the complete quick connect fitting.

View attachment 383249

View attachment 383250

View attachment 383251

Otherwise, I’d be real tempted to swap that thermostat out.

Ya heater and all worked before the swap! I’m gonna check everything everyone recommended and first probably change out that thermostat or at least test it and see if it’s opening and closing properly & ya I’ve delt with that heater hose inlet it’s a b****

 

[OR VietVet]

You have no idea of the age of that thermostat. Change it, period. Cheap insurance.

I also edited my response to your soft brake pedal problem in the other thread.

 

[ivin74]

Feel the coolant hoses to see if they are hot. If they not hot, replace the thermostat.

Test again if it's still not getting hot, remove the clutch fan and run the engine to see if it heats up. If it heats up your problem could be the clutch fan

 

[Holt50]

It's the temperature sending unit I just bought one today cuz mine is doing the same thing. I took a wire from the negative to the connector just to test my gage to see if it was working fine and it is.