Engine running hot, but heater not working?

[Scarecrow1]

Sounds like the thermostat is not opening and closing properly . Your heater core may be blocked ....to check this you could remove the return line and check the flow ..Hope this helps.......

 

[tm america]

i would get a inferred thermometer to see what the temp of the in and out is at the heater core .if the heater core is plugged only the in line will be hot if both are the same as engine temp i would look into making sure you dont have any broken vacume lines and that the actuator for the bypass door is working properly.if not it could be a bad heater control or bad vacume actuator or vacume leak somewhere

 

[rlwm211]

As a preliminary test you can feel the inlet and outlet of the heater hoses and see if both are "HOT". If so, I would suspect the adjustment of the blend doors. If for some reason the coolant filter is clogged, or even the wrong one, there would be no flow therefore no heat in the return hose.

If you replaced (Or someone else did) the heater core the mechanically controlled dampers may not be adjusted properly. It is entirely possible that one of the cable ends has come off of the levers.

According to Mitchell, you need to remove the glove box to access the top of the heater housing.

There are three cable controls.

One controls the blend of heat versus outside air. That one is located in the center of the cab, over the center hump.

The other two, one is a heater control, and the other is the defroster control, are located on top of the heater housing at the passenger end.

You adjust these by loosening the screw that holds the housing in place and adjust it for travel so that the desired function works properly.

I can email drawings if need be.

I would do the inlet, outlet temperature test before tearing anything apart. That should prove whether the heater core has flow or not.

Hope this helps


RL

 

[Somemedic]

I replaced the heater core ealier this year since I believe it was clogged. The above di-structions sound like what I need to do. However I dont see any vaccuum lines in the back. I only remember seeing the cables on the back of the housing. I certainly will chack and report back my findings.

For further info the 195F t-stat I just installed was $11 and according to another thread is the WRONG type for the 6.2 . Not sure how someone arrived at that fact but I will be ordering the $35 version (hockey puck) shortly. Not really sure what the diff is but if i need the other one then so be it. May try adding the 45degree elbow in the water pump and running the heater intake thru there.

 

[rlwm211]

The manual heater system for your truck does not appear to have vacuum lines for the controls. Everything is manual and uses cables.

The heater system is usually in the bypass circuit of the coolant system so that water circulates within that system regardless of the position of the thermostat. Otherwise you would not have heat when the engine has the thermostat closed.

If you have a coolant filter in the heater coolant hoses, it is possible the heater coolant circuit is "airbound" and cannot purge itself of the air and therefore is blocking coolant flow.

Newer cars actually have air vents built into the various coolant lines as it is a problem and these vents are needed to purge the air.

If the coolant filter is located higher than the top of the engine it may have trapped air in it. This is just a theory as I have not seen where you positioned the mount for the filter.

You need tp do the coolant temperature check on the inlet and outlet lines with the truck to temperature as that is the easiest way to verify that the coolant is flowing. You have to eliminate the question of whether the hot coolant is actually getting through the heater core, or not.

Once you resolve that question then it is a question of either correcting a coolant flow problem or figuring out why the heater plenum system is not sending the heat into the cab area.

Hope this helps

RL

 

[4bogginchevys]

I did read that you replaced core about a year ago..........my buddies 1009 had a problem just like yours where no heat got into the cab, after changing out radiators, burping the cooling system and confirming proper function of the thermostat........it turned out to be that a critter had built a blockage dead center between core and where air exits housing in front of 4wd shifter. He was not able to see it but when he reached in to double check for a clear path he hit gold! hope it's this easy for you too!

 

[tm america]

from what you are saying fixed it it sounds like you dont have it full of antifreeze. you should use a fill funnel as it gets the fuild level above the highest spot in the system thus eliminating air pockets. which will cause the t stat not to open and can make it overheat while not having heat.if you dont have a fill funnel you should have the heat on when filling the system this helps eliminate air pockets to

 

[ragedracer]

Well... Dangit. Problem's back.

Runs right at 190-195 at idle and slow driving. Take it on the freeway and the temp quickly climbs to ~210, and seems like it would just keep rising if I don't get off it. Heater blows hot.

This overheat issue only occurs at driving speed. Fan clutch seems good, I "tested" it against a know good fan clutch in an M1008. They both feel identical.

I replaced the thermostat with the correct "puck" thermostat. No change. Flushed out the system and replaced the coolant 70/30. No bubbles in the radiator nor has there been any loss of coolant. Also no oil in the coolant or coolant in the oil. So, head gasket seems to be OK. Radiator "guts" have some buildup.

Could I be looking at a clogged radiator? If so, is there anyway to test for that without pulling it? Could the waterpump be bad? The radiator cap?

I've never had a vehicle that only overheated when driving at 65mph and never at slower speeds or idle.

 

[ragedracer]

bump.

 

[ida34]

The clutch and fan should freewheel when there is independent airflow to the radiator. At 65 it should be uninterrupted airflow so it really should not be a factor on the freeway. I have heard about a water pump having the impeller come off with no outside indication but then it would overheat all the time. I would be willing to be you have a problem with your hoses or more likely, the radiator. Hoses can go bad internally causing a restriction. The radiator can go bad in two ways. Your fins could have problems. Are any folded over like someone brushed up against it? Folded fins can cause obstructed airflow. There are specific combs designed to straighten out the fins. You can also have fins that are deteriorating. They basically start disintegrating and either come out or crumb in place blocking airflow. The lack of fins will make the radiator less efficient. The tubes need the contact with the fins to get more cooling from the airflow. Tubes alone will not do the job without the fins. The other way for the radiator to go bad is internal obstruction either from calcium buildup or some other contaminant. I did not read the whole thread to see if you replaced the hoses but I would drain the coolant and check for the hoses by inspecting them off the truck. Look down the radiator through the opening. If you see deposits on the end of the tubes then they are restricting the flow through the radiator.

One other thing, are you using diesel coolant or the diesel additive? It is said the vibration of a diesel will cause cavitation. The cavitation will in turn cause air bubbles to form on the cylinder walls. This causes hot spots where the coolant is not contacting the cylinders. I do not know if this will be bad enough to cause and overheat condition but I thought I would throw it out.

 

[ragedracer]

The clutch and fan should freewheel when there is independent airflow to the radiator. At 65 it should be uninterrupted airflow so it really should not be a factor on the freeway. I have heard about a water pump having the impeller come off with no outside indication but then it would overheat all the time.

Right. I would tend to agree here. I don't think the problem is with the fan or clutch. The water pump also is probably not an issue.

I would be willing to be you have a problem with your hoses or more likely, the radiator. Hoses can go bad internally causing a restriction. The radiator can go bad in two ways. Your fins could have problems. Are any folded over like someone brushed up against it? Folded fins can cause obstructed airflow. There are specific combs designed to straighten out the fins. You can also have fins that are deteriorating. They basically start disintegrating and either come out or crumb in place blocking airflow. The lack of fins will make the radiator less efficient. The tubes need the contact with the fins to get more cooling from the airflow. Tubes alone will not do the job without the fins. The other way for the radiator to go bad is internal obstruction either from calcium buildup or some other contaminant.
I did not read the whole thread to see if you replaced the hoses but I would drain the coolant and check for the hoses by inspecting them off the truck. Look down the radiator through the opening. If you see deposits on the end of the tubes then they are restricting the flow through the radiator.

Hoses have been replaced within the past 16 months. Fins are all good. None of the issues above. There are, however, deposits on the ends of the tubes. They are all crusty. So, it sounds like the problem is likely flow. Is there a band aid fix for this? I tried flushing out the system but it didn't make a difference. Is there any "cleaner" that might help here? Or once it's that far is a rod out the only alternative? I'm trying to stay inexpensive as possible here. Business sucks and I can't really justify dipping too deep in my savings for what is essentially a toy. Any ideas from anyone on what it would cost to have a radiator rodded out if I pull it myself?

One other thing, are you using diesel coolant or the diesel additive? It is said the vibration of a diesel will cause cavitation. The cavitation will in turn cause air bubbles to form on the cylinder walls. This causes hot spots where the coolant is not contacting the cylinders. I do not know if this will be bad enough to cause and overheat condition but I thought I would throw it out.

Interesting. No I am not. I've never even heard of that. Some quick googling and I do believe I will add some. I don't think it causes an overheat issue but does seem to prevent corrosion of the water jackets.