Engine cools off when running heat

[ranger1943]

Flushed coolant, changed thermostat, water pump about 6 months ago when it was warmer. Now that it is winter (in MD) truck doesn't seem to warm up. Temp gauge gets into the lower normal range when idle and running. If I run the heat the temp gauge drops below the cold line. Upper heater hose is warm but not hot. Coolant levels are normal when cold and hot. Changed thermostat twice, verified operation on stove. I have also changed the fan clutch, seemed to help a little bit. If I run the engine without the fan it seems like everything is fine at idle, I didn't want to drive it without the fan though. I can hear the blender door operating and all comfort controls operate normally.

96 Ford Ranger XLT, 2.3L

Thanks.

Robert

 

[BRUTUS_T_HOG]

Well the heater is a small radiator and fan so depending on the outside temperature the engine cooling down is normal at idle.

It should stay at normal temp while driving with a load on the engine.

 

[Mark_88]

Sounds like an air lock in the system...remove the rad cap, run the engine till it is warm (5-7 minutes) and watch the coolant at that point...it should start moving...if/when the coolant level drops, top it up, cap it and test the heat...

Oh, and you should have the temp selector set to high and the fan on during this whole process...

If that doesn't do it, you may have either blockage in the heater rad core or there may be something wrong with the blend door not allowing the temp selector to function as it should (allow the heater core to blow warm air)...

Just hunches, actually...but probably an air bubble...

 

[ranger1943]

Just hunches, actually...but probably an air bubble...

Thanks for the reply, I have been thinking that all along. But it seems like all the air is out of the system. No coolant drop when running for several minutes, but I can squeeze the upper hose and it always seems empty. I let it cool over night and checked it this morning. Squeezed the hose and refilled the rad, ran it for 20 or 30 minutes and it seemed to heat up better, but engine temp immediately fell when I turned the heat on full. Upper hose was warm to the touch. Kept trying to squeeze air out and adding small amounts of coolant. Took it for a 10 mile drive and ran the heat full blast. Temp stayed right at the lower normal range line and heat was fairly warm the whole time. I figure I will let it cool off and do the same thing again. Seems to have gotten better so maybe I still have some air in there. We will see.

 

[tomw]

Both heater core hoses should be too hot for you to touch for more than a second or so when the engine is warmed up. I had loosen my back-flushing tee to let the air out in mine. Get it warm, and loosen while moving the hose so the uppermost part 'walks' to the tee. IOW, push the hose down, the air will move to the highest point. Move the hose so the highest point worms it way to where the tee is installed, or loosen the fitting at the heater core, and let the air come out. When you get that dribble of coolant, put the hose on tight, and tighten the clamp. You may have to park on a hill to get the bubble to go to where you can let it out. After that, both hoses should be about the same temperature.
tom

 

[ranger1943]

Both heater core hoses should be too hot for you to touch for more than a second or so when the engine is warmed up. After that, both hoses should be about the same temperature.
tom

Thanks Tom. I ran it yesterday for about 4 hours trying to burp the system. Took a long time to get barely into the normal range. After squeezing hoses I could get upper hose very hot. I would then turn on the heat and it would run very hot for about 5 min and then the engine would cool off and it would blow luke warm air. This went on for an hour or two, so I suspect I still have air in the system somewhere. The system still seems to accept coolant when I turn on the heat, it will take a couple of short pours and then stop taking coolant until I cycle the heat on and off.

Drove it to work this morning (18 miles) barely go above C and there was not heat. It was proably about 20 degrees outside.

I will give what you suggested a shot. The saga continues.

 

[RonD]

The t-stat should be a 192deg or higher for that engine.

The t-stat is there to maintain the lowest operating temp of the engine usually 200deg.
So don't use a 180 or 160 t-stat on these engines.

In some cases, and the Ford 4cyls fit this, the cooling system is too large for colder climates, but needed for warmer climates, so the "one size fits all" doesn't work well when outside temps get low.
People often cut a piece of metal or cardboard to put in front of the radiator to reduce air flow which reduces cooling, similar to what you did by removing the fan.
How much you cover the rad is something you need to test.
You can start with cardboard and once you find the right size then use a more permanent material that can be removed during the summer months.

Large semi trucks add snap-on or zippered covers over their front grills for the same reason, to block some of the air flow to the rad when driving in colder climates, so reducing air flow past the rad is a standard "fix" for colder climates.

 

[ranger1943]

The t-stat should be a 192deg or higher for that engine.

People often cut a piece of metal or cardboard to put in front of the radiator to reduce air flow which reduces cooling, similar to what you did by removing the fan.

Thanks for the response. The T-stat I put in is a 192, so we are all good there, unless I did it wrong. Not sure that is possible since it would only seat in the housing one way.

I have read a lot about the cardboard radiator trick. The problem I have with that is I have owned this truck for the past 15 years and have never had a problem with heat during the cold winters of CO and MD. I am pretty sure I had heat last month, so I think this is something recent. I think I either have an airlock condition that I am just now noticing since it has been cold, or something has failed, such as the water pump (although it is only 6 months old.)

Who knows? What I do know is that it is a very cold drive to work (in the 20's today) and the problem seems simple and is starting to aggravate me.

 

[RonD]

I would think an air lock or any air in the system would cause the engine temp to go up briefly until purged, not down.
Most thermostats now include a "jiggle valve", technical term.........really, lol.
A "jiggle valve" is a hole in the t-stat plate that allows air to escape when refilling the cooling system, or at anytime when t-stat is closed.
The hole has a metal pin in it that.......jiggles, to prevent hole from being clogged.
The t-stat should be mounted so the "jiggle valve" is at the 12:00 position, where air would be.

A t-stat or clutch fan problem are the only two thing I can think of that would cause an engine to run cooler than normal, and even the clutch fan would be iffy since the t-stat just wouldn't open as much if coolant was below 192deg after being through the engine.

read post #8 in this thread
http://www.therangerstation.com/forums/showthread.php?t=63552

 

[ranger1943]

Aggravated

Here is a recap from a very aggravated person:

96 Ford ranger 2.3L w/ AC. Engine temperature gauge barely gets into the normal range and no heat. About six months ago I changed the oil pump, timing belt, tensioner, plugs, wires, water pump, thermostat, coolant, oil, oil filter, transmission fluid, and air filter.

Truck seemed to run fine up until about 2 weeks ago. The engine temperature will not get into the normal range and I have no heat. I changed the thermostat/fan clutch and refilled the system. Coolant does not seem to really circulate but when I run the heat I could fill and add about a cup of coolant every 5 seconds for the rest of my life. There are no leaks so I do not know where the coolant is going. Oil looks fine, no sluggishness, coolant is neon green.

The upper radiator hose gets warm (not hot) and the heater hoses going to the heater control valve and heater core never really get that hot and feel very soft like there isn't anything in them. If I stop the fan and run the engine the coolant gets hot and engine warms up a bit. The inlet heater hose gets pretty hot and the outlet hose stays fairly cool. Upper radiator hose gets cool when heat is running. I have unplugged the inlet and outlet hoses to the heater core and fluid came out of it so it seems like it is circulating I guess.

Doing some research it seems like I have two problems

1. clogged heater core
2. open thermostat

But I have changed the thermostat, and if I stop the fan I can get decent heat but the engine still doesn't really get that high up to temp.

Bad water pump? I don't see any fluid leaking out of the pump weep hole or housing and I can see the bearing spinning so it seems to be operating unless the impellers broke, it is only about 6 months old.

I am going to take the T-stat housing apart again Friday and make sure the T-stat is seated correctly in the housing as indicated in the thread of RonD post. I really don't want to but now that I think of it even when i finished all the work 6 months ago and it was hot out I recall the truck running very cool as well. This would indicate that the original "new" thermostat might have been installed improperly by yours truly.

 

[RonD]

A water pump issue would cause warmer engine temp.

Yes I would pull the t-stat...again....and check how it sits in the housing, both sides, if it is not a tight fit coolant will bypass it around the edges.
The deeper and larger spring end always goes towards the engine on t-stats.

I would also test it while it's out, put it in a pan of water, fully covered by the water.
Heat up the water, water boils at 212deg, t-stat should be fully open only just before the water boils, or if you have a thermometer... it should be fully open at 192deg, only slightly open at 185deg.
If you live in Denver, 5,000 ft above sea level, then water boils at 203deg , so altitude matters.

My 4.0l must have a slotted rubber gasket around the t-stat plate or it will not be tight in the housing.

As another test get a metal coupler and a couple of hose clamps, connect the IN and OUT engine hoses for the heater together, so bypass the diverter/valve and heater core.
Or if one of the heater/engine hoses is long enough just remove the other hose, so a straight IN to OUT on the engine heater connections.
This will tell you if there is any funny business going on with the heater assembly.

For possible air issues.
You can buy a plastic Engine Flush coupler, these have two heater hose connections and screw on cap, so similar to a "T" coupler.
You install this on the higher of the two heater hoses, you cut the hose to install.
This allows you to fill and bleed the air from the system as this is on the engine side of the t-stat.

 

[ranger1943]

Success!

Turns out stupid me had the thermostat not seated properly in the housing. The cab of my truck is like a SAUNA! And it seems to be idling better. Thanks to all that took the time to reply. Feel free to call me a moron

 

[Mark_88]

Awesome...thanks for the update...

Did you know that there is an R in the middle of the moon?

 

[Tedybear]

Turns out stupid me had the thermostat not seated properly in the housing. The cab of my truck is like a SAUNA! And it seems to be idling better. Thanks to all that took the time to reply. Feel free to call me a moron

Ok you're a moron.

Feel Better?


Now that we've got that part out of the way? Job Well Done on figuring it out. You didn't give up, and you kept at it until it was resolved..

S-

 

[kimcrwbr1]

I didn`t see it mentioned but a good way to burp the system is park it on a steep hill front uphill open the radiator and turn the heater on high with the engine hot. top it off and then fill the overflow tank up to the line with coolant. How old is the radiator cap put a new one on and make sure the overflow tube is not sucking air when the engine fully cools down.