Weak heat in every TM I have owned?

[Lee'sdaytona]

Greetings,
Why is it every TM I have owned, my first 87 Daytona, my 89 Caravan and my 86 Daytona all have weak heat? The caravan and the 86 Z I replaced the thermostat and heater core, as well as it has a new radiator.
The van heat works just well enough to take the edge off. The daytona is slightly worse. Plus, both vehicles run cold, according to the gage. The daytona barely moves at all away from COLD. Gage works because it overheated once and read correctly. Temp starts to rise while in traffic or at a light. Will rise about 1/8 up the gage.

Stock thermostat seems to be 195*, is it OK to run a hotter thermostat? I even tried one without drilling the hole in the thermostat with little improvment.

Perhaps the weather stripping around the heater core should have been replaced to help channel all air through the core?
Thanks for any help!

[raccoon]

Make sure its a 195°, ive found 192° and 180° in these cars before. drilling the tiny hole will make a difference, ive stopped doing it and fix the factory bleeder problem.
I also don't use the 4way coolant valve. I think it helps a little.
You should check the blend door adjustment cable. its "auto adjusting" but sometimes things dont work out right. take the cable off and move the divider door all the way full heat, check to see if the cable can push it just as far.

but most likely your heater core is just full of crap and plugged. CLR works very well for cleaning it out. try reversing the lines, might be a temp fix but you'll know if it was plugged.

[Lee'sdaytona]

Make sure its a 195°, ive found 192° and 180° in these cars before. drilling the tiny hole will make a difference, ive stopped doing it and fix the factory bleeder problem.
I also don't use the 4way coolant valve. I think it helps a little.
You should check the blend door adjustment cable. its "auto adjusting" but sometimes things dont work out right. take the cable off and move the divider door all the way full heat, check to see if the cable can push it just as far.

but most likely your heater core is just full of crap and plugged. CLR works very well for cleaning it out. try reversing the lines, might be a temp fix but you'll know if it was plugged.

There is no possible way the heater core is plugged. It is a brand new core, brand new radiator, and brand new coolent. The blend door could be a cause, but still doesn't explain why the engine is running so cold, till it comes to a stop.
-Lee

[raccoon]

try a new brand of thermostat?

[bgbmxer]

There is no possible way the heater core is plugged. It is a brand new core, brand new radiator, and brand new coolent. The blend door could be a cause, but still doesn't explain why the engine is running so cold, till it comes to a stop.
-Lee

Did you flush everything after all that swapping. Doesn't take much to clog that stuff. Also. Can you feel the hoses and see if the rad hoses are hotter than the ones going to your heater core?

[85boostbox]

Sounds to me you have the thermostats in backwards

[x.Gen]

hey Lee, how ya been? still lovin on those seats bud...

starting with the basics - don't trust the temp gauge. the terminal to the temp switch tends to stretch from being tugged on over the years. I've personally had it go from functioning normally to not, completely randomly but visibly; I looked at the terminal receptacle on the harness and had seen where it needed to be pinched to get consistent contact. Temp SWITCH, not temp sensor.

start with the hoses, as said earlier - when the car is hot (as it can get), car running crank the heat, check the heater hoses. with a new core, they should both be hot. both cold - check the heater control valve for the vacuum line from the firewall (and if it is connected, make sure it isn't fractured, can fracture ANY where - note valve actuator position, move temp to cool, position should change). if your rides aren't getting up to operating temp in the first place - could be too big of a bypass drilled into the t-stat, or sometimes you get a box from the parts stores that has been swapped, you need to check the stamping on the t-stat. I got slipped a 165' in a 180' box once...other than that, carefully check the rad/hose to see that they are hot.

the stock cores are slight, maybe 5/8" thick core if I remember. aftermarket replacements are thicker. I wouldn't do the core without the blower motor, original are both inferior to aftermarket as I've seen. if you didn't PROPERLY bleed the coolant when you installed, it can take quite a while to work all the air out before you'll get full coolant circulation (to the core). don't waste your time doing the CLR. I stretched my last core with CLR in extended soak, followed by water and air pressure clearing. barely improved. all else right in the coolant system, you should get enough heat off a new core to bake your feet pretty well. if not something is off, usually simple once you find it.

[bgbmxer]

We use a descaler for heat exchangers in the heat and Ac business. But I don't think that's the problem honestly

[Lee'sdaytona]

hey Lee, how ya been? still lovin on those seats bud...

starting with the basics - don't trust the temp gauge. the terminal to the temp switch tends to stretch from being tugged on over the years. I've personally had it go from functioning normally to not, completely randomly but visibly; I looked at the terminal receptacle on the harness and had seen where it needed to be pinched to get consistent contact. Temp SWITCH, not temp sensor.

start with the hoses, as said earlier - when the car is hot (as it can get), car running crank the heat, check the heater hoses. with a new core, they should both be hot. both cold - check the heater control valve for the vacuum line from the firewall (and if it is connected, make sure it isn't fractured, can fracture ANY where - note valve actuator position, move temp to cool, position should change). if your rides aren't getting up to operating temp in the first place - could be too big of a bypass drilled into the t-stat, or sometimes you get a box from the parts stores that has been swapped, you need to check the stamping on the t-stat. I got slipped a 165' in a 180' box once...other than that, carefully check the rad/hose to see that they are hot.

the stock cores are slight, maybe 5/8" thick core if I remember. aftermarket replacements are thicker. I wouldn't do the core without the blower motor, original are both inferior to aftermarket as I've seen. if you didn't PROPERLY bleed the coolant when you installed, it can take quite a while to work all the air out before you'll get full coolant circulation (to the core). don't waste your time doing the CLR. I stretched my last core with CLR in extended soak, followed by water and air pressure clearing. barely improved. all else right in the coolant system, you should get enough heat off a new core to bake your feet pretty well. if not something is off, usually simple once you find it.

Yeah, I'm pretty sure the T-stat is not in backwards, as I have changed them several times and I know the brass end with the spring goes in towards the head, and the shorter side points outward. I don't think I even drilled the hole in the last ones I put in the cars. I will check the stamping as far as temp. I can't remember at the moment if the daytona still even has the heater control valve. I never thought of changing out the blower, however, the air it is moving, is lukewarm at best. I am also fairly certain my gage is working, even though not much else works in the car
By the way, glad to hear you are lovin those seats! I'm so happy I didn't have to trash them. Did you need/want the back seats that match those? I now have black leather waiting to go in and the red ones are in the car. I can't remember if I offered them to you last time.
-Lee

[x.Gen]

thanks, and no on the back seats - usually prefer a rear bench delete on my daytona's, even though the originals are in good enough shape. anyhow, a vast improvement with what you provided, thanks so much.

without the control valve, heat should be VERY effective, you should have coolant flowing to the heater core constantly that way. and regarding the foam around the heater core, yes - that's pretty much a necessity, you need to force the air to go thru the core for the full benefit. if you pull it apart again to do the blower motor I would for sure replace the foam if needed.

[Ondonti]

3.0's don't have any of that extra stuff, they don't need a hole drilled because they have a bleed, and one of my cars has this problem. I would think its the blend door. Air should be more then lukewarm even if your Tstat is 160 degrees. I went to 192 from 180 and it didn't really help. That same car also runs very low on the temp gauge whereas my wife's 3.0 runs more around the middle. Only time the temp guage gets hot in my "cold" car is when towing another car in town. Then it gets into the middle.

According to my megasquirted car which I can read exact temperatures, the thermostats are very accurate.

[wallace]

If you deleted the heater control valve you may need to install a restrictor on the outlet. If the valve is installed and is backwards you will run colder than normal. Post a pic of the heater hoses at the firewall.

[crusty shadow]

Greetings,
Why is it every TM I have owned, my first 87 Daytona, my 89 Caravan and my 86 Daytona all have weak heat? The caravan and the 86 Z I replaced the thermostat and heater core, as well as it has a new radiator.

thats because all 3 of them have blown the head gasket. no heat, car runs cold until you come to a stop, and you've replaced just about the entire cooling system with no change in temperature.
unfortunately those are all the classic symptoms of a blown head gasket or a badly cracked head. i experience the exact same problems you have and each time its been a head gasket.
dont bother messing with the blend doors or anything else to do with the heater- you're wasting your time. it doesnt matter what you do to the heater core to get more airflow through it- engine coolant is not getting up to temperature therefore you will not have heat until you can get the engine to stay at a stable temperature near the oem operating temperature.