I'm still struggling with a basic 98 1500WT with a 4.3L, Not equipped with AC. Came in for low heat, acted just like low coolant. Level was OK. Put in a new stat. Its cold as heck outside right now so warm up takes a little. New stat functions correctly but still gotta rev it up to get heat. Pull it in, flush system with flush. Put acid type rad cleaner right in core hoses and flush core with garden hose-got good flow. Same thing gotta rev it up for heat. Pull water pump impeller looks good-put new on any way...NOW ITS WORSE. Very little warmth when I feel heater hoses. As far as I know there is no valve on this model only a blend door which is working, besides if the blend door was failing the hoses should still be hot. Can the intake be plugged that tight? I will reflush again tonight-I work nights. And I am gonna try to put the power washer directly in as many outlets and fittings I can. This is a very basic set up and I am embarrassed that I can't figure it out!
- Thread starter redtom
- Start date
Russ from MN
Well-known Member
- Location
- Bemidji MN
Wow, that has to be frustrating! I have heard of hoses separating internally and acting like a check valve.
Super-H-Mike
Member
I have seen , as I am sure you have too, ports that are completely crusted over and plugged with Dexcool remnants. The fact that the new water pump made it worse makes me wonder though.....
Not an expert, but I'm willing to brainstorm with you a little.
I had the 4.3 in an S-10. Did the the same thing. I had to flush out the heater core with the hose and that fixed it. All kinds of gunk came out. Sounds like you did that. It might be worth another shot.
I also had an issue with an intake manifold gasket. I can't tell you exactly what it was, but I was losing coolant into the oil pan.
Is it possible the belt or tensioner isn't quite working like it should? If there is slack, maybe the water pump isn't turning quite like it should? Just a thought and something I would look at if it were mine.
Good Luck.
I had the 4.3 in an S-10. Did the the same thing. I had to flush out the heater core with the hose and that fixed it. All kinds of gunk came out. Sounds like you did that. It might be worth another shot.
I also had an issue with an intake manifold gasket. I can't tell you exactly what it was, but I was losing coolant into the oil pan.
Is it possible the belt or tensioner isn't quite working like it should? If there is slack, maybe the water pump isn't turning quite like it should? Just a thought and something I would look at if it were mine.
Good Luck.
Determined
Well-known Member
Just thinking out loud.
.
Fan clutch locking up?
Does it have a howling sound at idle?
Temporarily cover rad to see if it will warm up.
Is system buiding up pressure when warm?
What is the temp guage reading?
A new thermostat is not always a good thermostat.
.
Fan clutch locking up?
Does it have a howling sound at idle?
Temporarily cover rad to see if it will warm up.
Is system buiding up pressure when warm?
What is the temp guage reading?
A new thermostat is not always a good thermostat.
Have you replaced the heater core ?
On the Buicks and Cadillac's they used to replace a lot of them for low heat problems. The cores from GM were better too. The aftermarket did not heat as good. Once out pry the end cap off and I'm betting you will see a lot of brown sludge in it.
On the Buicks and Cadillac's they used to replace a lot of them for low heat problems. The cores from GM were better too. The aftermarket did not heat as good. Once out pry the end cap off and I'm betting you will see a lot of brown sludge in it.
Let me try to answer your tips: Temp is going up to proper temp and I can see the slight fluctuation as it opens and closes. The fan clutch is free and does not appear to be locking, There is pressure in the system when I stop it. I did flush the core and did get some gunk. I blew through it with my mouth to see how much back pressure but no new one to compare. I will flush again. Belt is good and tight. Is the core replacement a tough job on this one?
jimg.allentown
Well-known Member
How about making a few simple tests....
Check the flow and pressure to the heater core. Take the hoses off the heater core and point them into a bucket. See what kind of flow you have. Try plugging the inlet hose while it is running, and see if it is developing pressure.
Right off the bat, this should tell you if it is a flow problem or a plugged heater core. This will isolate the problem to be either flow from the engine or a problem with the heater core.
Just having good flow does NOT insure that you will have good heat. I have seen cores that have had good flow going through them, and still would not deliver heat. After taking one of them apart, found that only a few tubes in the center of the core were flowing. Replacing the heater core solved that problem.
How about coolant temperature? MEASURE IT!!!! Do not trust a gauge. Put a thermometer into the radiator, and see for real what the temperature is running when it is warmed up.
While the system is a simple one, you cannot see inside of the system to see the problem. And, in this day and age, we are running vehicles long past what used to be called the end of life for a car or truck. In the old days, a car was shot around 100k miles. Today they are running 200 to 300 thousand miles. This brings about a whole host of new and unexpected problems.
Check the flow and pressure to the heater core. Take the hoses off the heater core and point them into a bucket. See what kind of flow you have. Try plugging the inlet hose while it is running, and see if it is developing pressure.
Right off the bat, this should tell you if it is a flow problem or a plugged heater core. This will isolate the problem to be either flow from the engine or a problem with the heater core.
Just having good flow does NOT insure that you will have good heat. I have seen cores that have had good flow going through them, and still would not deliver heat. After taking one of them apart, found that only a few tubes in the center of the core were flowing. Replacing the heater core solved that problem.
How about coolant temperature? MEASURE IT!!!! Do not trust a gauge. Put a thermometer into the radiator, and see for real what the temperature is running when it is warmed up.
While the system is a simple one, you cannot see inside of the system to see the problem. And, in this day and age, we are running vehicles long past what used to be called the end of life for a car or truck. In the old days, a car was shot around 100k miles. Today they are running 200 to 300 thousand miles. This brings about a whole host of new and unexpected problems.
redtom,To check disconnect both heater hoses from the engine.Check heater ports on engine to be sure they are not plugged or partly plugged up.Connect a length of hose between the the two ports refill and start.Check the hose to see if it gets hot.I it gets hot and you have good flow through the heater core it should work.
At the risk of sounding dumb-which should be the inlet? The hose from the tube on the pump? Or the one from the intake? The one from the intake is the one that is getting warm. I always thought the tube from the pump was the one that pumped all the time through the core. Note:this is the pump with two small tubes -one to core- the other bypass? to engine. Also, someone "on the net" said there are CW and CCW pumps. Is this true?
Steve@Advance
Well-known Member
Since the hoses are not getting hot, it's back to restricted flow or lack of volume/pressure from the pump.
Try removing the return hose from the core, see what kind of volume you get through the core. Probably not much.
Then remove the supply hose from the core, see if there is volume there. If not, there is a restriction in the fitting from the intake, or airlock. If there is good flow, the core is still plugged.
Thinking possibly the acid flush turned some sediment loose and it immediately plugged the core again. If you haven't already done so, flush the engine with the core supply hose disconnected, a hose running in the radiator, drain cock open, engine at high idle. That should get anything loose flowing around out. Then back flush or replace the heater core.
Try removing the return hose from the core, see what kind of volume you get through the core. Probably not much.
Then remove the supply hose from the core, see if there is volume there. If not, there is a restriction in the fitting from the intake, or airlock. If there is good flow, the core is still plugged.
Thinking possibly the acid flush turned some sediment loose and it immediately plugged the core again. If you haven't already done so, flush the engine with the core supply hose disconnected, a hose running in the radiator, drain cock open, engine at high idle. That should get anything loose flowing around out. Then back flush or replace the heater core.
The hot water exits the intake and flows through the heater core and on to the INLET side of the waterpump.
The port the heater returns to is in a common area to the big hose barb on the pump that connects to the lower radiator hose.
Hot water exits upwards from the front of the heads, into the intake manifold, flows though an area in the intake manifold that heats the fuel mixture, then exits upwards at the back of the intake through the clever pot metal quick connector into the heater hose.
Have you checked the quick connector? There's a rubber washer flow restrictor in the connector that can clog or get deformed/crushed nearly closed when the pot metal fitting corrodes and deforms.
Older engines with "V" belts used CW waterpumps, serpentine systems the drive the pump off of the flat back of the belt run CCW.
The vanes on the impellers have the opposite slant between the two pump rotations.
If you got the correct part number for the year/model it SHOULD be correct!
The port the heater returns to is in a common area to the big hose barb on the pump that connects to the lower radiator hose.
Hot water exits upwards from the front of the heads, into the intake manifold, flows though an area in the intake manifold that heats the fuel mixture, then exits upwards at the back of the intake through the clever pot metal quick connector into the heater hose.
Have you checked the quick connector? There's a rubber washer flow restrictor in the connector that can clog or get deformed/crushed nearly closed when the pot metal fitting corrodes and deforms.
Older engines with "V" belts used CW waterpumps, serpentine systems the drive the pump off of the flat back of the belt run CCW.
The vanes on the impellers have the opposite slant between the two pump rotations.
If you got the correct part number for the year/model it SHOULD be correct!
dick1234
Member
- Location
- Atkins, Iowa
Do you have good air flow through the heater core? Mine was plugged with corn chaff (bees wings). Had air flow, but not enough.
It could be your heater core is plugged. purge flush system and use a strong vinegar solution to break up the scale in side the water jackets. You may have a bit of luck and not have to replace the heater core.:shock:
The out side air flow could be cut off too like a radiator with dirt between fins cutting off air flow.
good luck..
The out side air flow could be cut off too like a radiator with dirt between fins cutting off air flow.
good luck..
Bryan inIowa
Member
I have seen the fitting coming out of intake manifold get plugged up . That goofy quick connector . Pull it out of manifold and check it over
My heater on the 98 Dodge Dakota is lousy. I have done little to check it out. I did get out the temp ray gun and decided that first off I need a new thermostat as temp was only about 150 on heater hoses and radiator hose. But, hey, I don't drive much in the winter anymore, and it will soon be spring. I did take the grilling (or what ever you want to call it) off between hood and windshield, hoping I could look down in with my two bit flexible scope but could not see the heater core for external crap plugging it. The hoses do get to almost equal temp so I feel core is not restricted too bad anyway. On tractors, I used to pull the return hose off heater and check the flow and often times to bleed them after a repair job. Some day, I just may do that and flush it and put in a new stat. Have one laying on the front seat. Pickup is too long to get in the garage though so will wait until warmer weather, and then, well, like I said, who nead's a heater in the summer.
fixerupper
Well-known Member
I have seen a chunk of blue silicone plug the inlet of the heater.
john *.?-!.* cub owner
Well-known Member
Have you tired using a fitting to loop the heater hoses back on itself at the heater. If hose gets hot them, only place left is core. If still not hot, go to other end of hose and look for plug. Is this a sudden problem, or just kept getting worse and worse till not enough heat to be able to drive?
Allan in NE
Well-known Member
Restrictors are blown at the intake gaskets.
Allan
Allan
BANDITFARMER
Well-known Member
A couple things come to mind. 1 The water pump is bad (worn impellers) 2 May sound dumb but is the belt on right? 3 Has it had intake gaskets replaced? (Maybe put in wrong or wrong gaskets) 4 Did you burp the heater core? (air locked) 5 Have you checked for a blockage in the heater hoses at the engine and there fittings? I have run a wire down inside the fitting in the block and found a blockage.
I have worked on several 4.3 all with the same problems you list. And all of them were one of the problems listed above. It seams the 4.3 is a little fickle in the heating and cooling system for some reason. Bandit
I have worked on several 4.3 all with the same problems you list. And all of them were one of the problems listed above. It seams the 4.3 is a little fickle in the heating and cooling system for some reason. Bandit
Pair-a-dice farm
Well-known Member
I went though the same thing with a 95 C1500 4.3. Before I got it someone put the wrong antifreeze in and plugged the heater core so I changed the heater core. Still no heat. Someone told me the restrictor in the intake gasket so I had that changed. I also changed the dash control and thermostat. I also changed the water pump thinking that it may not be pumping enough to keep it from overheating but not enough to heat. Still no heat. Finally I decided that a heater hose had collapsed on the inside. I took the front one off and it was stopped up with crud at the fitting. I don't know why I didn't see that when I changed the pump but anyway that was the problem.
RandyB(MI)
Well-known Member
If I remember correctly, your first post on this mentioned that it worked just fine with plenty of heat AS LONG AS IT WAS REVVED UP OR GOING DOWN THE ROAD. Since you've changed the pump/impeller and flushed everything then I'm going to go out on a limb here and say you have an air lock and it is caused by a partially blown head gasket pressuring up the system. I've had three do this exact same thing. '81 5.7 diesel Caddy , 2.2 Dodge Shadow and 3.4 GM V6. When you put air under pressure into that system it will airlock and stop circulation until rpm of impeller overrides it. Not just an opinion, it has happened to me and your 4.3 isn't immuned to it . Simple test is bubbles in rad. or put an exhaust sniffer in rad.
Hobo,NC
Well-known Member
- Location
- Sanford, NC
double naut whut bob said... I recommended you check the hose and connections for restrictions :roll: Coolant flow can be checked no guess needed... Keep in mind if you go there you will have to keep the radiator full of water while you check it...
MarkB_MI
Well-known Member
- Location
- Motown USA
I'm with Randy on this. Blown head gasket is highly probable, assuming you haven't already run a cooling system pressure test, which is the FIRST thing you should have done.
I have the same problem with my 98 blazer with a 4.3
I found the fitting on top of the engine had a small rubber orfice in it that had swollen which I took out and it helped. If you use acid in the core you need to keep it circulated for a while not just sit there. I heard the 4.3 were good for corroding and clogging up the cooling system. I tried a new thermostat and water pump too. Pump was leaking but replacing both items didn't help the heat problem. I have some heat now and figured it was good enough. I did put an inline strainer in my heater hose that supplies the heater core. Can't believe how much it filters out. It is an 80 mesh screen.
I found the fitting on top of the engine had a small rubber orfice in it that had swollen which I took out and it helped. If you use acid in the core you need to keep it circulated for a while not just sit there. I heard the 4.3 were good for corroding and clogging up the cooling system. I tried a new thermostat and water pump too. Pump was leaking but replacing both items didn't help the heat problem. I have some heat now and figured it was good enough. I did put an inline strainer in my heater hose that supplies the heater core. Can't believe how much it filters out. It is an 80 mesh screen.
I have a 2004 GMC that did that, flushed it with rad. flush no change. Mixed up a strong solution of CASCADE dishwashing powder, added to the system, ran till warm then back flushed the heater core. Did that one more time, then flushed the whole system with clean water. Been 3 years and no more problems
ETxJohn
i
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