well I pulled back the cover on the heater core and its odd because the thing is ice cold, it doesn't get hot. as for the pressure in the heater core lines, there is a little but I don't think its that much... if the heater core is cold but not leaking is it bad?

 

I've seen people put shut off valves on the hoses, and I once had a IROC that some one had looped the back heater hose because the core leaked. If that not the case then I would replace the hoses and the core. If the core has coolant to it, it should warm up.

 

I've seen people put shut off valves on the hoses, and I once had a IROC that some one had looped the back heater hose because the core leaked. If that not the case then I would replace the hoses and the core. If the core has coolant to it, it should warm up.

I know thats what I can't figure out, because I can feel heat from the hoses and on the top hose there is a small thing with a cap on it about 6 inches from the firewall and I took the cap off and there is coolant coming out so I know it has a little bit of pressure but the heater core is still cold.... pretty weird...

thanks for your help though!

 

Are both Heater lines Hot after the car is running?

the Heater core could be clogged which also would cause no heat.

That cap you checked was a flushing kit "T" remove it, I have one crack ona friends 88. Also there is no Heater control valve on the 88. Also what thermostat are you using. If you havea 160 that could be causing the lower temperature from the Heater..

I can help more after you respond to the questions above

 

Heater Core

:agree:

... on the top hose there is a small thing with a cap on it about 6 inches from the firewall and I took the cap off and there is coolant coming out so I know it has a little bit of pressure but the heater core is still cold.... pretty weird... thanks for your help though!

That sounds like a coolant flush kit. Is it the same size and look like an adapter for a garden hose? Is it allowing coolant to flow past it?

It sounds like your heater core or related hoses.

Diagnosis
With coolant full & ENG at operating temp:

Set TEMP to FULL HOT
Set blower to HIGH
Set any mode except OFF

Place hand CLOSE to lower hose (caution it can be hot)
Compare to upper hose, which should be cooler.

If both hoses are hot and about the same temp, check for heater core or hose restrictions.

[CSM, 1990, 1B1-8]

Let us know,
D

 

Are both Heater lines Hot after the car is running?

the Heater core could be clogged which also would cause no heat.

That cap you checked was a flushing kit "T" remove it, I have one crack ona friends 88. Also there is no Heater control valve on the 88. Also what thermostat are you using. If you havea 160 that could be causing the lower temperature from the Heater..

I can help more after you respond to the questions above

I haven'te checked both lines only the top one because I thought it was the one that was flowing into the heater core, could be wrong though and that one was hot. im pretty sure its a 180 and not a 160 because at idel the car will reach temps of 220

c5d im going to give that a try a little later today and let everyone know tonight, thanks very much for everybodys help!!!

 

I know thats what I can't figure out, because I can feel heat from the hoses and on the top hose there is a small thing with a cap on it about 6 inches from the firewall and I took the cap off and there is coolant coming out so I know it has a little bit of pressure but the heater core is still cold.... pretty weird...

thanks for your help though!

I'm not exactly sure what you checked. There is a control valve that sits in the area you are talking about that shuts off the flow to the heater core. You could try taking the valve out of the circuit and connect the two ends together and see if you get any heat.

There are two coolant lines for the heater. One comes from the front of the car, connects to the heater control valve, and then goes into the firewall and eventually the heater core. Then there is the return line that comes out of the firewall, goes into a t-fitting that has one side that is the coolant return from the EGR valve and the other going forward somewhere.

 

I'm not exactly sure what you checked. There is a control valve that sits in the area you are talking about that shuts off the flow to the heater core. You could try taking the valve out of the circuit and connect the two ends together and see if you get any heat.

88s don't have the control valve.. At least my friends 88 doesn't and as far as I know it is stock.

I know for sure that 89-later don't have it as well

 

88s don't have the control valve.. At least my friends 88 doesn't and as far as I know it is stock.

I know for sure that 89-later don't have it as well

I'm not 100% about this on an 88 either. I would expect some changes when the LT1 was introduced and the coolant flow was reversed.

Since the later cars don't have this valve, how do they keep the coolant from flowing through the heater core when the heat is off?

I would put a valve in the line, but if someone came up with a better idea I'd like to know about it.

 

on my 89 Coolant is always moving through the heater core

 

cold heater

Try taking that contoller out, and unplugging it and
cleaning contacts with a pencil earser. That's what
gordon KILLERBREW recommended at a semiar this
summer. Had similar problem on 89, that trick didn't
fix mine had to change programer(on firewall in behind
brake petal). You can get under dash on passenger
side and disconnect linkage to damper door, in heater
box, it is hooked to a small electric motor, that moves
and controls location of damper door. This door contols
how much heat or cool that comes out vents. you can
now move this linkage by hand and control heat by hand until problem can be pinpointed. used mine for
6 months this way. You can not get a new cotroller
from GM

 

got some new news, sorry it took so long I went out on vacation.

just got back from messing with the car, I took both hose's off the heater core, stuck a hose up to it and water ran threw it just fine, took the other end of the lower hose that goes to the intake manf. off ran the garden hose threw it and water ran threw it just fine, then I stuck the garden hose up to the intake manf. were the heater hose went to, water went threw it and came out of the other hose just fine.

put everything back togeather, started the car back up, let it get up to 200 and pulled the cover back from the heater core again and the thing is still ice cold, checked the hose's, the top one that goes to the water pump gets hot enough so I can feel it but the lower one that goes to the intake manf. I can't even feel the heat from, stays somewhat cool.

can anyone figure this out?

 

Re: cold heater

Try taking that contoller out, and unplugging it and
cleaning contacts with a pencil earser. That's what
gordon KILLERBREW recommended at a semiar this
summer. Had similar problem on 89, that trick didn't
fix mine had to change programer(on firewall in behind
brake petal). You can get under dash on passenger
side and disconnect linkage to damper door, in heater
box, it is hooked to a small electric motor, that moves
and controls location of damper door. This door contols
how much heat or cool that comes out vents. you can
now move this linkage by hand and control heat by hand until problem can be pinpointed. used mine for
6 months this way. You can not get a new cotroller
from GM

 

WOnder if the T-stat is still the problem.. for the $10 it would cost it is worth a shot

 

WOnder if the T-stat is still the problem.. for the $10 it would cost it is worth a shot

you think it could be the thermastat? would that keep coolant from going to the heater? if so ill give it a try tommorow

 

you think it could be the thermastat? would that keep coolant from going to the heater? if so ill give it a try tommorow

Well I don't know for sure but it would not hurt to try.

It just does not make sense that one line is Cool and one warm if there is fluid going through the heater core. If it is not the Thermostat which it may not be, I would still think it is the heater core, just by the way it is acting..

 

Well I don't know for sure but it would not hurt to try.

It just does not make sense that one line is Cool and one warm if there is fluid going through the heater core. If it is not the Thermostat which it may not be, I would still think it is the heater core, just by the way it is acting..

I just don't want to take the heater core out but if I don't figure out what it is by the end of the week ill give it a try

 

I just don't want to take the heater core out but if I don't figure out what it is by the end of the week ill give it a try

I Don't blame you i would not want to either.. I did it with the 89 dash.. was a 5 hour total job..

good luck

 

88 CORVETTE

BEFORE I TOOK HEATER CORE OUT. I WOULD TAKE

BOTH LINES OFF HEATER CORE AND BLOW THRU

HEATER CORE WITH COMPRESSED AIR, SHOULD

TELL YOU IF ANTHING IS FLOWING THRU CORE

+ MIGHT UNCLOGE IT IF IT IS STOPPED UP.

WHAT DO YOU GOT TO LOOSE, YOU'RE ON THE VERGE

OF A MONUMENTAL TASK!!!!!!

 

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.

 

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.

 

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

 

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: