Radiator hose temps?

Picked up a winter beater/dump runner/landscape supplies hauler. Has a 3.9 V6. Vehicle calls for a 195* thermostat.

Problem is good airflow from heater but poor heat. I was getting ready to back flush the heater core but happened to have my infrared temp sensor handy so I checked all the hoses.

Readings were taken after running errands for an hour (ambient temp was about 40*F), gauge is about 1/4 of the way between "C" and "H".

At hot idle the upper radiator hose reads 150-160* depending on exactly where I point the laser. The lower hose I don't recall but it was plenty cool.Heater hoses read 140* and 130* with the heat selector on full and fan on #2.

Do I have a clogged heater core or is the t-stat stuck open/missing?

that would be the first thing I would check

Could be stuck but I had t stats actually fall apart into pieces.

One other thing, lack of heat to the heater is usually the first sign of low coolant, wouldn't hurt to check.

Sounds like the T stat is tired. A new one would hopefully fix your problem.

Way back in the mid 80s Chrysler suggested you replace the thermostat and gasket every 2 years. The reason was because the old ones would deteriorate and would open before reaching the desired temp.

Low heat out put, first thing to check is the coolant level and freeze protection. The second thing to do is replace the thermostat and gasket. Back flushing the cooling system every 4-6 years is a great idea. After that, you troubleshoot the condition of the heater core. Gene

I have a 99 CTD and he heater has sucked donkey balls since day one.

And I live in CA where it never ever gets below 25. Ever

Did you buy it new? Have you ever changed the thermostat? Has the system ever been back flushed? A 195 thermostat will help a heater put out more heat than a 180 thermostat will. If the stat has been changed and the heater still sucks, I would look at the blend doors in the heater unit and be sure all the doors are opening and closing like they are suppose to.

I've also heard the the radiators are so big on the diesels that the coolant never can stay at the stat temp. On those, you have to restrict the amount of air passing through the rad in the winter. But then, that falls into the troubleshooting area I mentioned in the earlier post, doesn't it? Gene

I put in a new 195* thermostat (the old one was a 195* and was complete) and flushed the heater core both directions until I got clear water both ways. Lots of rusty water, no noticeable chunks. Admittedly this was hard to do in 28* weather when the end broke off the garden hose. Topped off the coolant (I always drill t-stats if they don't have a vent)in the rad and overflow and took it for a drive...low heat output. The rad needed about another cup of coolant the next day...still low output.

The core was flowing clean water although I can't say if it was flowing as well as it should since my garden hose/heater hose mating wasn't optimal.It was a solid stream coming out but my water pressure is about 70 psi so it was spraying all over the place on the inlet side. Me and the hose were like

The cable adjustment has good tension and I can clearly hear the "klump" of the blend door opening and closing when sliding the heat selector back and forth.

It took a long time to get the feeling back in my hands and I likely will need a new garden hose come spring so right now I'm just going to think on this one for a bit. If anybody has a first gen Dakota and an infrared thermometer I'd appreciate if you could check your hose temps against mine.

actually that was a good thing that you inadvertently modulated the hose psi into the heater core cuz it ain't meant for anywhere near 60 psi. it may or may not handle 60 but it dont take that to clean it out. I'm thinking from your descrip that the core is flowing well enough (especially with the backflush) & that the prob (the heater core heat output) is elsewhere.

I've always used compressed air to blow them out and have never had one leak after. I'd change the core if you don't get heat after blowing out and also check the blend door while you have the box out.

Alright but I think a core would need a liquid going the other way (reverse flush) to get the loose debris out of there

ive had 2 dakots that had heater problems,i replaced the core on both of them,one works great,the other just wont make much heat,all the doors etc work as they should,i even put a 205 degree stat in it and it just gets slightly over warm air,never could figure it out
i have also pumped warm oxiclean water both ways thru heater cores with good success

One good diagnostic for the basic cooling system would be to temporarily install a mechanical temp gauge and check temps. An inexpensive one from the AP store would do fine. This is much more accurate than a temp gun on rubber hose. After a good run you should see 195+ with a 195 stat.

Be careful of using an infrared temperature gun for diagnostic work such as this. The emissivity (a measure of the efficiency in which a surface emits thermal energy) can vary greatly from one material to another and one color to another. Unless you have an infrared temperature gun that can be calibrated to a given material and color, the temperature readings you are getting could be way off.

Also, I have '87 Dakota with the 3.9L engine and although the temperature gauge always stays near the cold end of the gauge, the heat is good and warm even in the coldest northeast weather.

The heater hose has an air lock and needs bled. The same thing happens to my '94 3.9 Dakota. One of the heater hoses loops way up and over the engine and is prone to air locks. I cut the hose at the top of the arc and installed a Prestone flush & fill tee. If an air lock develops, I loosen the cap and let the air out.

This has been in the back of my mind. The truck has exactly what you describe already installed in the upper heater hose. My hands were too dang cold to loosen that cap the other day so I hoped for the best. I'll put more effort into that when I get back to it.

My other thought was maybe the impeller on the pump is rotted away and I'm just not getting enough "flow" for the heater.

Pressure check the cap, most vehicles of a cab- foreword design will not get heat to heater correct if cap is not holding proper pressure, this learned the hard way on a 85 Caravan years ago.

How big is the hole your drilling in the thermostat? You need to bleed the air at that top heater hose. A good rad cap is required to keep the coolant full any place near the top of the rad level. Once the air is purged from the system, it needs to remain sealed or the air pockets return. Any coolant leaks increases the chance for air to get back into the system.

Does the temp gauge show the motor is warming up? If it does, check the temp at the outside of the heater core with your inferred, both sides should be the same temp. If the temp varies more then 10-20 degrees, the core could be the problem. Turn off the heater fan for this test! The heater fan can cool down the heater core by several degrees in a very short time, especially if its cold. Check metal fittings if possible. Hoses do not give good readings.

Though a real temp gauge with numbers on it would be better, you can get an idea of the motor temp with your inferred at the intake manifold just below the thermostat housing. You can also check the temp of the rad core tubes at the bottom and at the top of the rad. You can see about what temp the coolant is flowing through the motor. You have to check the temp of the metal that surrounds the parts the coolant flows through for the most accurate numbers, and they will still be off a bit, but if everything is checked the same way, you can get an idea of what its doing.

I have to ask, how long is the motor running before you are expecting heat? If everything is working properly, it will take at least 10 minutes running time before the system BEGINS to produce heat, and another 10 minutes to show heat in the cab. If you have the heater fan on high during this time, you can almost double those times! Its amazing how many people have the heater fan on high and wonder why it takes so long for the ride to warm up. Are you expecting that little heater core to displace all the cold air in your cab instantly, but your not even letting it warm up first? Gene