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-=Jeff=- said:
on my 89 Coolant is always moving through the heater core
If the later cars are always running coolant through the heater core it would mean that they would control the temp by opening or closing various "doors" in the ducts.

If you've confirmed that there's no blockage in the coolant flow to the core I would start looking at the blend doors and what ever controls their function. I would guess that the one that opens the flow from the heater core is not opening.
 
Discussion starter · #22 ·
stu said:
If the later cars are always running coolant through the heater core it would mean that they would control the temp by opening or closing various "doors" in the ducts.

If you've confirmed that there's no blockage in the coolant flow to the core I would start looking at the blend doors and what ever controls their function. I would guess that the one that opens the flow from the heater core is not opening.
were is the blend door at?

RPolley

I stuck a garden hose up to the heater core after taking both lines off and water went threw it just fine.
 
Blend doors are in the dash, but I don't think that would explain why one return line is cool. I never noticed one cooler then the other with my heater going.

There is one door to look at and that is the Temp Control Door found on the heater box. Another controls fresh air from the outside (mainly closed in AC MAX)

also there or others but they only control which vents the air will go through.
 
Discussion starter · #24 ·
I got a buddy that has a heater core laying in his garage, im going to pick it up today and hook the lines up to it and see if it gets hot, that should tell me if its the heater core or not. thanks again everyone for your help
 
Of course if your system is pure stock (you suggest a flush kit has been added), the size of the hoses dictate their connection points. But if that has been modified by mistake, it could account for your problem.

According to the '90 Service Manual the lower hose is the hose which should be hot and warmer than the upper hose.

You indicate the upper hose is hot while the lower hose is cold.

I also think you've indicated that you can get water flowing through the heater core. If this is correct, then there is (probably) no heater core blockage. If you haven't verified flow in both directions, perhaps do so.

I suspect the flow through the heater core will only be one way. I also suspect the hot hose needs to be on the bottom. If flow is one way, and the hot going in is against the flow direction, there will be no flow or heat.

So if you can confirm flow through the heater core only goes in one direction, make sure the hot inlet is with the flow.

Or just swap out the top hose with the bottom hose and see if things change.

As for the thermostat affecting the heater flow only, I doubt it. The engine would be affected with a bad T-Stat as well.

JAT
D
 
Discussion starter · #26 ·
I went and bought a haynes manual and it says that there is supose to be a heater control vavle, sits in the engine compartment right next to were the two hose's come to the heater core...

my car does not have one... could this be the problem? :huh:
 
88corvette said:
I went and bought a haynes manual and it says that there is supose to be a heater control vavle, sits in the engine compartment right next to were the two hose's come to the heater core...

my car does not have one... could this be the problem? :huh:
No. The heater control valve found in the engine compartment is an OFF/ON valve designed to close the coolant flow to the core when no heat is wanted.

Without one, the coolant will merely flow into the core and should allow for heat.

If you system has a ON/OFF coolant flow valve in the passenger compartment, that is closed, it would account for no heat.

C'ya
D
 
Discussion starter · #28 ·
some more new info!

took both hoses off again, water flows threw the heater core in both dirrections...

anyways turned the car on with the hoses off and very little water flowed threw them

so now im wondering if its the waterpump not pushing the water threw like it should... :huh:

only other thing is on the upper hose witch goes to the water pump, down towards the water pump there is an L conection and then about another foot of hose that goes to the actual water pump... is this some sort of control valve?
 
88corvette said:
some more new info!

took both hoses off again, water flows threw the heater core in both dirrections...

anyways turned the car on with the hoses off and very little water flowed threw them

so now im wondering if its the waterpump not pushing the water threw like it should... :huh:

only other thing is on the upper hose witch goes to the water pump, down towards the water pump there is an L conection and then about another foot of hose that goes to the actual water pump... is this some sort of control valve?
That 'T' goes to the Oil cooler..
 
OK, I have to jump in here. Let’s stick to the basics and forget about the FM because there is none…we’re talking simple physics here guys. The heater core is nothing more than a small radiator or heat exchanger. The thermostat does not affect the heater core because the water going thru it comes from the heads if it’s configured properly. All the T-stat does is allow water to flow thru the radiator when the temp is high enough – water flows through the heater core whether the T-stat is open or closed. You indicate that the temp is around 200 so we’ll assume the problem is NOT the water temp not getting hot enough. Therefore, the only way you could have this problem is if there is no water flowing thru the heater core…period. All you have to do is figure out why. There are a few possibilities and, as we all know, there are different configurations for different vettes. I’ve never seen a car without a heater control valve. Look at a basic automotive guide. There is always a valve that opens and closes to allow water to flow through the heater core. I haven’t looked at either one of my vettes yet but I bet they both have them (85 and 89). Not sure how you could control the passenger temp without one. Anyway, the only accurate way to check flow through the core is to run the car with the return hose open into a container. This will indicate you have true flow through the core. Also, check the flow going into the core, compare the two; if the water pump is good, you’ll know by the rate the water comes out of the hose. This should tell you if you have a weak water pump or a clogged core or blockage prior to the core. It’s that simple.

Keep in mind here I’m relying on your observations. Things like the water temp and the core not getting hot are crucial to this diagnosis. The fact that one hose going into the core is hot is not necessarily an indication that water is flowing thru it. Heat can radiate thru the rubber of the hose. Check it with the car’s system, not an external source. You must be sure of these facts to isolate the problem. Good luck!


:cheers:
 
jpshark said:
I’ve never seen a car without a heater control valve. Look at a basic automotive guide. There is always a valve that opens and closes to allow water to flow through the heater core. I haven’t looked at either one of my vettes yet but I bet they both have them (85 and 89). Not sure how you could control the passenger temp without one.
There is NO Control Valve in the 89!!!!

infact my 84 Camaro never had one either. the is coolant always flowing through the Heater core
 
-=Jeff=- said:
There is NO Control Valve in the 89!!!!

infact my 84 Camaro never had one either. the is coolant always flowing through the Heater core
Jeff, I beleive you, however, that means the heater core is always hot, that's where the heat comes from, it's very simple. My '85 has a valve. My '85 GM manual refers to it and shows the location. My Haynes manual for '84 to '96 Corvettes describes removal and replacement of the valve, no indication it doesn't exists on specific models. I also have an '88 Olds 98 (in mint condition BTW :thumbsup: ) and a GM manual for it. There is a temp control valve on that car as well. Again, the "GM" manual shows the location of it and describes the R&R procedure. Frankly, if you don't have one, my guess is it was removed by someone. Like I said, I don't see how you can control the passenger compartment temp without one.

Based on his observations, I believe there is no water flowing thru the heater core, that's the only logical explanation for his problem. He indicated the core is not clogged - that means there is no water "flowing thru" the core, any obstruction in the circuit that prevents water "flow" will prevent the core from getting hot. My company manufactures medical equipment that is water cooled. We use a heat exchanger with a "PENN" valve to control the flow thru the exchanger - it's on the output side, in other words, it doesn't matter where the valve is, all it has to do is control the "flow" in the circuit, it's that simple.

88corvette, take the hose off going into the heater core and start the motor to see if water is getting thru the hose and at what rate. Then take the hose off on the output side where it returns to the main system. Again, check for flow and at what rate, compare the two. This is simple though messy. You might want to drain the system of coolant and use straight water for this test. I'm sure you'll find an obstruction in that circuit somewhere. Good Luck!

:cheers:
 
jpshark said:
Jeff, I beleive you, however, that means the heater core is always hot, that's where the heat comes from, it's very simple. My '85 has a valve. My '85 GM manual refers to it and shows the location. My Haynes manual for '84 to '96 Corvettes describes removal and replacement of the valve, no indication it doesn't exists on specific models. I also have an '88 Olds 98 (in mint condition BTW :thumbsup: ) and a GM manual for it. There is a temp control valve on that car as well. Again, the "GM" manual shows the location of it and describes the R&R procedure. Frankly, if you don't have one, my guess is it was removed by someone. Like I said, I don't see how you can control the passenger compartment temp without one.

Based on his observations, I believe there is no water flowing thru the heater core, that's the only logical explanation for his problem. He indicated the core is not clogged - that means there is no water "flowing thru" the core, any obstruction in the circuit that prevents water "flow" will prevent the core from getting hot. My company manufactures medical equipment that is water cooled. We use a heat exchanger with a "PENN" valve to control the flow thru the exchanger - it's on the output side, in other words, it doesn't matter where the valve is, all it has to do is control the "flow" in the circuit, it's that simple.

88corvette, take the hose off going into the heater core and start the motor to see if water is getting thru the hose and at what rate. Then take the hose off on the output side where it returns to the main system. Again, check for flow and at what rate, compare the two. This is simple though messy. You might want to drain the system of coolant and use straight water for this test. I'm sure you'll find an obstruction in that circuit somewhere. Good Luck!

:cheers:

I agree as well with what you stated, but When i bought my car it was bone stock without a control valve, which I know causes coolant to move through the heater core all the time. As for how it controls cooler or warmer air int he car I am uncertain without looking at the GM Service manual, which I have at home, not here at work. I remember reading why it chnged and how it works without it but cannot find it at the moment.
 
-=Jeff=- said:
I agree as well with what you stated, but When i bought my car it was bone stock without a control valve, which I know causes coolant to move through the heater core all the time. As for how it controls cooler or warmer air int he car I am uncertain without looking at the GM Service manual, which I have at home, not here at work. I remember reading why it chnged and how it works without it but cannot find it at the moment.
I guess the damping system/blower combination determines whether the hot air being generated by the core is used in the passenger compartment or not. Sometimes I marvel at how engineers (I'm one) can take something so simple and make it more complex. Bottom line is, everything is based on simple concepts and that's usually the way to find a problem....keeping it simple. Have a good one!

:cheers:

I just thought of something. My '85 has standard heat/air, my '89 has electronic climate control which is one of the most difficult systems to troubleshoot. I wonder if the existence of a valve is determined by which system you have? Which does yours have?
 
OK,

Here's what I've gathered so far:

1) 88Corvette has verified that his heater core flows water both ways (which it should)

2) He has no stock control valve (I don't know whether an 88 should have one or not, but the absence of one should make this problem easier to solve), and he does have what sounds like a flush kit installed in one of the lines.

3) Both hoses flow water, so no restrictions there.

So here's where we're at. The water pump isn't pressurizing the heater core properly. If it were, then the heater core would be getting hot coolant flow, and it would be heating up.

My next step would be messy, but I'd disconnect both hoses from the intake manifold and the side of the water pump, and I'd start the engine. coolant should shoot out of the hose connection on the side of the water pump, and the intake manifold connection should just trickle a little out until the T-stat opens. The hose adaptors that are attached to the water pump and intake are iron, and the internal diameter in the intake manifold one is only about a quarter inch, so they can get clogged, and the internal flow passage from the water pump impeller to the high pressure heater line is pretty small, so it can clog up, too. Since you have eliminated the possibility that the restriction is in the hoses, or the heater core, it MUST be the water pump, or the return point on the intake manifold where the flow is being restricted.

I'd also remove that flush kit or whatever it is and splice that section of hose together. Maybe the flush kit's internal diameter is too tight or something and it is restricting the flow rate of the hot coolant...?

That's all I can think of. Good luck.
 
Discussion starter · #36 ·
once again let me thank everyone for their help!

I have taken both hoses off before and started the car, very little coolant comes out of the one coming from the water pump, and a little bit does trickle out of the one from the intake. I would say the one from the water pump comes out in little burst of coolant, not a constant fast flow at all.

as for what system do I have, I have the one with just buttons, not nobs or levers to move, all electronically controlled and this may be why I don't have a heater control valve, I am going to get a new water pump this weekend and put it in to hope this is the problem.

at one point I did hook a garden hose up to the intake hose and water flew threw that hose, threw the intake and out the water pump hose just fine, but I think the water pump is just not pushing the coolant like it should, im not sure if its the original but im pretty sure it probably is and the car has 148k miles on it so it woln't hurt to put a new one on anyways.

once again thanks to everyone here at DC for your help :cool:
 
-=Jeff=- said:
I agree as well with what you stated, but When i bought my car it was bone stock without a control valve, which I know causes coolant to move through the heater core all the time. As for how it controls cooler or warmer air int he car I am uncertain without looking at the GM Service manual, which I have at home, not here at work. I remember reading why it chnged and how it works without it but cannot find it at the moment.
GM controls the heat output with what they call a blend door. The door opens to pull air around the heater core not through it when no heat is needed. Full heat the door situates so to pull all the air through the heater core. To vary the temp a combination is used some through the core some around it.
The shut off valve when used is closed or open no variance inbetween. They use that valve to completely close the hot water going to the heater core so when the AC is on no heat is coming into the system so maximum cold air temp. is acheived. They are vacuum controlled.
My 72 that had AC had no heater valve. My 85 has a vacuum controlled heater valve with AC with regular controls. 1986 is the first year for electronic climate control.
 
I Have a service manual for 89 vette. Got it straight from

local dealership. The 89 vette with climate contol does

not have any kind of diverter valve in line to stop water

flow thru heater core. Water is flowing thru heater core

even when using A.C., you only put hot air in duck

work when you need heat!!!!!! Explained about this

operation in earlier post. 88, you better start looking

inside car guarntee that's where your problem is.

Wasting time under hood since you are getting water

thru heater core, even if your not getting enough water

you would still some heat , if you had any contol of

of door on heater box(which contains heater core).

You oviously are not opening that door.
 
Ah the wonder of these...

What should be a simple problem and solution.. sure can get sticky..

I'm gonna add strictly from experience. Every car I've ever worked on with heater core or cooling problems, I've never come across a car that had weak pressure to the heater core (input side). Except those that had hose blockage build up from years of neglect. I have seen hoses crudded up to almost complete closure.

I agree with keep it simple. Figure out why you have low hose pressure to the core.

Rather than start up the engine, I'd rig up a hot water line from the house (a water bed filler valve and garden hose should do it). Let the hot water flow through the core and straight out. See if your heater system works that way. If it does, you can rule out the diverter doors and everything in the heater system.

Concentrate on the engine delivery side of the equasion.

If it doesn't heat with good hot water pressure, you can concentrate on the heating system itself.

JAT
D
 
Discussion starter · #40 · (Edited)
***UPDATE****


Edit: got it to work, check out the other thread!!!

good news is that sometimes the car would reach temps of up to 215 degree's while driving and with the new water pump and 192/195 thermastat the car never went above 195 at all, usually ran around 193
 
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