Weak Heat/never warms up

[Dr.Evil]

Not that the weather is getting colder, I've noticed once again that the heater in my car sucks and the car never seems to warm up fully. I swaped out the 180* t-stat for the factory 195, didn't help. On the freeway the temp gauge never moves off cold, and the heat is not very warm out of the vents. Any idea on what would cause this?

[LowSL2]

Did you purge the cooling system of air? Is the radiator topped off with coolant? I had the same problem when I was really, really low on coolant.

[turbovanman²]

Are you sure its the 195 stat? it should say the temp at the bottom of the copper pellet. Did you drill the 1/16" bleed hole?

Get it nice and hot, check the upper and lower rad hoses, the top should be very hot, the lower hose much cooler, if so, then the rad, thermostat are working. If both are cold, the thermostat is no good.

Now, if upper hose is hot, lower cold, check the hoses going into the heater core, the innie should be hot, outie cold, if not, its probably plugged up. Remove the hoses, get some new hose and make some extensions. Blow out the water and install the new hose, zip tie so there facing up. Fill the core with CLR and let it sit for an hour or so, now reaim hoses so there facing down and blow out the heater core backwards with warm, forceful water. I have to do this every year on my van, too lazy to put a new heater core in.

[Tony Lane]

Flush your heater core. I had the same problem with my Daytona. Did a full coolant system flush, worked.

[Dr.Evil]

cool ill try that this weekend. and no I didnt drill a little hole in the t-stat....

[R/T]

ALSO:

Make sure the hoses to / from the motor to the heater valve are correct, there is an "in" on the valve marked with an arrow to show flow direction.

Should be the "L" shaped one on the end.

The 2 next to each other got to the heater core.

4th one is return to the water pump. :thumb:

This did make a difference on my wagon.

[turbovanman²]

The flow into the heater core doesn't matter, its built so either port will work. After back flushing it, reversing the hoses might not be a bad idea. Also, if you have a/c, you might have one of those vacuum valves on the heater hoses, make sure thats working or installed correctly-its designed to block coolant flow when the a/c is on, so the a/c doesn't deal with heat from the heater core, which equals colder a/c, :clap:

[Big_P]

I solved this problem in my P-body by covering 2/3rds of the radiator with plywood.

[csx452]

Did you use a Mopar thermostat? I've swapped several aftermarket ones and found them all to be bad. Every time I use a Mopar one, it works first time every time. My buddy just had the same problem with his K-car. He finally decided to do what I told him and he bought one from Dodge. It now works great and he has heat again. Most garages around here won't use aftermarket ones for the same reason. For a couple of bucks more you should get a Mopar one. Even if your heater core is plugged, the temp guage should rise when the engine is warming up. Check the top hose to see if it is getting hot.
Frank H.

[csx452]

One more thing. I had a 91 Spirit 3.0 that my kids used to drive. They complained that there was only a little heat and that the guage was only rising a little. Turns out they had the button pushed for air conditioning. That was making the fan run and cooling everything down. I turned the air off and there was plenty-o-heat. Gotta love those easy fixes. Hope your's is easy too.
Frank H.

[turbovanman²]

Did you use a Mopar thermostat? I've swapped several aftermarket ones and found them all to be bad. Every time I use a Mopar one, it works first time every time. My buddy just had the same problem with his K-car. He finally decided to do what I told him and he bought one from Dodge. It now works great and he has heat again. Most garages around here won't use aftermarket ones for the same reason. For a couple of bucks more you should get a Mopar one. Even if your heater core is plugged, the temp guage should rise when the engine is warming up. Check the top hose to see if it is getting hot.
Frank H.

I use GM thermostats on the 3100 engines for that exact same reason plus there a mother?%$&^@$#^@$^ :censored: to get at. So far, haven't seen a crappy aftermarket one but I'll remember what you said later down the road, :thumb:

[mario03SRT]

My 89 2.5 is giving me a hard time too.

I manually opened the control valve to be sure that it was not vacuum issue. The inlet hose to the heater core is hot and the outlet a bit cooler. I will do a core flush to see if this helps. The heater/defrost blows maybe 60 degrees and outside it was 20 feg F.

Marion

[iangoround]

My old acclaim would have great heat if it wasn't too cold out, or I was sitting at idle. However, once I started moving it would blow lukewarm.

I came to the conclusion that the new radiator I had installed earlier that year was just "too efficient" and the engine couldn't keep up when it was really cold out or i was moving at any substantial speed.

[altered7151]

I know how you can fix it Matt, move to Florida. It was a bitter 62 degrees this morning. I must be getting used to it because I actually turned the heater on.

My charger used to do the same thing in Reno when it was super cold, the dry cold air makes the radiator super efficient and it would never warm up. Of course that was with the 180 t-stat and I was too lazy to change it. I cut a piece of cardboard that covered half the radiator and it worked wonders when it was super cold. Plus side is the same air that makes the radiator too cold also makes the intercooler cold, and its cold dense air going into the turbo. Then again its hard to get traction when the asphalt is 28 degrees.

[speedfreek500]

I had the same problem too i put a dodge t-stat in and did the liquid draino (plus )trick for an hour and WOW i had heat.Good luck.

[speedfreek500]

oop's liquid draino (PRO)

[moparzrule]

My daytona didn't have heat, backflushed the heater core and then all was well.
Right now in my shadow I did not even use the splitter box thingy, just ran straight lines to the heater core. I had a 94' dodge ram and in the summer time the A/C wasn't very cold and I couldn't figure out why. Well stupid dodge never stops the hot coolant from going through the heater core they just use a trap door in the heater box to block off hot air. Well after 12 years the trap door wasn't working so well so I had heat coming out with the A/C. Simple solution, go to Home Depot or Lowes and buy a ball valve with 5/8'' barbed fittings and install it in the feed line. Shut off the flow in the summer time! I plan to do the same thing to the shadow once it gets hot again. Although I don't have A/C, it still blows slightly warm even when you slide the selector over to cool.

[86Shelby]

Simple solution, go to Home Depot or Lowes and buy a ball valve with 5/8'' barbed fittings and install it in the feed line. Shut off the flow in the summer time! I plan to do the same thing to the shadow once it gets hot again. Although I don't have A/C, it still blows slightly warm even when you slide the selector over to cool.

I'd be weary of doing that on one of our engines since the coolant needs to flow through the heater hoses to keep coolant circulating through the engine when the t-stat is closed. I would just get one of the factory style valves to ensure you don't have issues caused by no coolant flow.

[moparzrule]

I'd be weary of doing that on one of our engines since the coolant needs to flow through the heater hoses to keep coolant circulating through the engine when the t-stat is closed. I would just get one of the factory style valves to ensure you don't have issues caused by no coolant flow.

Not sure why coolant *needs* to flow through the heater core. I had my lines plugged off completely in the summer time, no lines were hooked up to the heater core at all. I had no issues. Coolant does not need to keep circulating when the T-stat is closed, not sure who told you that but they are wrong.
If you are seriously worried about flow keeping on going, run a loop from the water pump to the head where the heater line comes out. But like I said, I had both plugged off this past summer with no issues.

[2.2turboscotty]

i would get a factory valve instead of one of the ball valves, i have one on the B250 and it started to leak when i opened the valve after being closed for the summer. i didn't know that about the flow, why doesn't my n/a circle track car overheat then? i am not running any hoses other than the radiator hoses and even in it at WOT all the time it stays at 190 deg all the time.

[moparzrule]

Where did you get the ball valve from? Sounds like a really crappy one. The one I got was solid brass and very large and heavy, like what you use for the water shutoff in your house.
And like I said already, no you do not need constant flow.

[2.2turboscotty]

i was asking 86Shelby why we need flow to the core. i got mine at a hardware store some time ago for something else and just ended up using it for that, it's not brass it looks more like stainless steel or something but i think it was for house plumbing or something. when i opened the valve it reminded me of when you go to fix a sink or tub and you shut the valve off and then it leaks untill you reopen it. i sure you have had that happen.

[turbovanman²]

I'd be weary of doing that on one of our engines since the coolant needs to flow through the heater hoses to keep coolant circulating through the engine when the t-stat is closed. I would just get one of the factory style valves to ensure you don't have issues caused by no coolant flow.

Yeah, I agee. For some loopy reason, the heater core acts as a waterpump bypass and if you block it off, the coolant temp fluctuates like crazy. Looping the hoses is a good idea but messy. :p

[moparzrule]

i got mine at a hardware store some time ago for something else and just ended up using it for that, it's not brass it looks more like stainless steel or something but i think it was for house plumbing or something. when i opened the valve it reminded me of when you go to fix a sink or tub and you shut the valve off and then it leaks untill you reopen it. i sure you have had that happen.


Yeah thats not the same at all. I'm talking more the like the valve that shuts the water off to your whole house, one big lever that turns 90 degrees and it's shut off.

[2.2turboscotty]

i wonder why the circle track car stays at 190 no matter what? i guess i should just shut up and be happy with it, i was one of the only guys not having overheating issues last season, after i cut some slots in the nose for more air flow. something went right for me, no way?

[moparzrule]

Yeah, I agee. For some loopy reason, the heater core acts as a waterpump bypass and if you block it off, the coolant temp fluctuates like crazy. Looping the hoses is a good idea but messy. :p

I had no problems with my car, and I had both CB and non-CB engines in my car. Started out with an 88 T1 engine with the regular rotating pump, and now it has an 89 CB 2.5L with the counter clockwise pump and I've had both plugged off with no erratic cooling issues.
And why is looping the hoses messy??? It gets them out of the IC lines way, in fact you'll barely even see the line at all since it runs right down.

Also, on older cars and trucks the way the heater was configured was a line out to a valve in the heater core line, and how much heat you receive was how much the valve was opened. So if you had it on full cold, the valve was shut (and did not route anywhere else) so that means no coolant flow. They didn't seem to have any issues.

[BIGBRUDDA]

If you'se guyz have a HOT heater coil.The next thing to check is the "blend door "( mixes hot&cold air). Its attached to the "slider bar" via cable.:(
a) pull the heater control.......... Carefully!!
b) slide the ring end off the slide bar linkage.
c) check for " slight resistance" when pushing or pulling the cable. Look for kinks. Listen for a"THUNK" when it closes.:nod:
If it free slides ...........ya gots prollemms.:banghead:
The bell crank tab and shaft at the other end( you can barely see with a flashlite & a squint) is PLASTIC . And notorious for breaking!!:confused2:

If thats it .PM me and I'll instruct you on an "ALTERNATE" control method.:eyebrows: :clap:

[86Shelby]

i was asking 86Shelby why we need flow to the core.

No, it doesn't need to flow through the core. Miscommunication there. I was suggesting to not simply stop all coolant that would normally flow through those lines. Run a line from the T-stat housing to the lower hose/WP housing to keep the coolant from being stagnant near the t-stat.

On many engines that you can put a ball valve in a heater hose the engine will have it's own bypass hose that runs from the t-stat area to the water pump. Take a look at a small block Mopar, Chevy, Ford 5.0, big block Chevy, Buick 3.8, even a Slant 6 and a Chevy BlueFlame 6. They all have a dedicated hose that runs from the area near the T-stat to the WP to keep coolant circulating throughout the engine at all times. The heater hoses on the 2.2/2.5 also do that job in addition to feeding the heater core. Go ahead and put the valve in the hose to stop it going to the core, but at least provide a way for coolant to circulate through the engine.

[Turbo3Iroc]

My DD Spirit R/T has pretty much the same issue with heat. When I am on the highway it will pretty much never go past the first line of the normal range. I had to block off part of the rad with cardboard to get enough heat in the car for a long trip. Lately for my 13 mile commute to work I have had about 2/3 of the rad blocked off by the cardboard. That's fine as it never really gets hot on the way to/from work. But running around shopping today I was doing a lot of city driving and it got up to the 2/3 line and I heard the fan come on but the needle wouldnt go down. So I pulled the cardboard up about halfway where I had it for my trip and it was better.

The rad on this car is pretty good. I have only 13K on it since it was hot tanked and pressure checked. The heat started blowing real hot as the temp got up there.... Anyway, just some feedback for you guys thinking about doing this. If you do a lot of city driving keep an eye on the needle, etc.