Chevy Impala SS Forum banner

1 - 13 of 13 Posts

·
Registered
Joined
·
340 Posts
Discussion Starter #1
Friends I am having a problem solving my new heat situation and requesting your thoughts, comments and hopefully solutions. I will start with letting you know what I currently have. Vehicle has 6,700 miles since restored, brand new LT1 (355) with less than 3K miles. New "BeCool" radiator, 9C1 hoses, new thermostat, new OEM heater core less than 1K miles ago, (old one turned out to be very clean). This past Wednesday I did also replace my original A/C compressor with a new Delphi compressor, AC Delco accumulator and orifice filter. Blower motor works fine. AC blows out of all vents cold.

Problem is no heat? When the vehicle was stripped for paint and engine work the entire drive train was also removed. I do recall the vacuum canister being removed too.

When I turn the control over to heat I can not hear the heater door opening, thought I used to hear that? Am I wrong?

I am thinking I have a vacuum problem but not sure how to identify it, where to start looking or how to rectify it?

Any words of wisdom would be very much appreciated!

Most respectfully,
Larry
Deputy347k9
 

·
Registered
Joined
·
11,207 Posts
It could be a blocked vacuum line (everything else works I assume), the vacuum manifold, the vacuum motor is not working, or the linkage for the motor is not attached (correctly).
 

·
Banned
Joined
·
3,437 Posts
this a 1996 model , if so both hoses to heater core must be hot. if not then the heater core is the problem . the heater core is / acts like a filter . how many miles on the heater core ? also what is your coolant servicing . type of coolant concentration and type of water used .

if its 110 deg F and the ac is on max cool the heater core has full flow [1996] unless someone changed it and put a valve in the heater hose line.[non oem]
 

·
Registered
Joined
·
340 Posts
Discussion Starter #4
As I stated in my initial write-up, OEM heater core less than 1K miles ago, the old one I pulled out was actually in very nice condition. Today the odometer turned 6,740 miles, AC running at 40 degrees.

When you turn the know over to heat from AC do you hear the heater door opening? I thought I use to hear that? There are no vacuum leaks related to the engine as it runs like a scalded dog!

Is there a way to check the vacuum at the AC/Heat control knobs?

Larry
 

·
Registered
Joined
·
11,207 Posts
You may hear the door move, but they are relatively quiet.


If there is no indication of a vacuum leak when you switch the knob to heat, you probably do not have a leak. That does not mean that you do not have a vacuum problem.


If you pull the hose off of the heat door motor (when the engine is running and you have selected heat), and feel suction, you can assume it is either the vacuum motor, linkage, or the door is blocked. Strange things have been found in the HVAC system of these cars, and there may be something blocking the action of the door. The only access to the door is through the drip pan on the passenger's side. The vacuum motor is on the passenger compartment side of the duct, and should be able to be accessed from the steering column access panel, ash tray opening, or below the dash front.
 

·
Banned
Joined
·
3,437 Posts
the question is are both heater core hoses hot ,, very hot. if so then its a HVAC box issue . there is a temp door in there and it maybe stuck with no air filters and this design strange things can get inside there.

If BOTH HOSES ARE NOT HOT THEN ITS A FLOW ISSUE THRU HEATER CORE.

Only you will be able to fix it .
 

·
Registered
Joined
·
340 Posts
Discussion Starter #7
J cat, both hoses are hot and without any question what so ever there is not a flow issue. I agree with you that there has to be a HVAC box issues.

Fred, thanks for the advise on checking this out. I will again crawl under the dash, remove the drip pan and check things out. Should have done that when replacing the heater core!

Thanks to all for the advise. Anymore will be gladly accepted!

Larry
 

·
Banned
Joined
·
3,437 Posts
J cat, both hoses are hot and without any question what so ever there is not a flow issue. I agree with you that there has to be a HVAC box issues.

Fred, thanks for the advise on checking this out. I will again crawl under the dash, remove the drip pan and check things out. Should have done that when replacing the heater core!

Thanks to all for the advise. Anymore will be gladly accepted!

Larry
yes I think you are correct that when you installed the heater core you messed up the temp door operation. both hoses are hot so that means that heater core is probably 170 deg f. the door must be stuck or linkage issues. hopefully not the temp control knob...

post back what it was . tough to get at this stuff..
 

·
Registered
Joined
·
340 Posts
Discussion Starter #9
J Cat, I did not mess up the operation of the temp door when installing the heater core, the heat did not work prior to my installation. I changed the heater core thinking that might be the problem. Sort of R & R parts as I go along! During the time I restored this gem I had the entire drivetrain out of the vehicle, glass removed, bumpers, moldings, seats, carpet, console and even the dash pad was removed and replaced.

Prior to the restoration I did have heat and defrost, after the restoration I have had nothing? So.... I screwed up something along the line.

I have eliminated:
1. Engine is completely new
2. New BeCool radiator
3. New OEM NOS heater core
4. 9C1 hoses that both get hot


I guess the only avenue of approach now is with vacuum. Soon I will start taking some of the trim off the dash so I can check the AC/Heater control unit, will also remove lower pan and check the vacuum attachment to the door plus linkage. Praying I find the problem and resolve it.

Due to serious health issues I have not been able to work on the girl as much as I would like, this has been an issue for 4 years now! Time to figure it out as this is the only issue I have with the car.

Will keep you updated, I promise.

Larry
 

·
Registered
Joined
·
7,988 Posts
Before pulling the HC lower cover off, be sure to check the vacuum lines in that area. You should hear "hissing" sound when cycling the knob on the AC panel. If not, it's a good chance the line is off somewhere. Don't think this would affect the engine at all as I believe there is a check valve somewhere in the vacuum lines.
 

·
Registered
Joined
·
11,207 Posts
There is a check valve that does not allow the vacuum to escape from (ambient air pressure to enter) the heater manifold, but it does not stop the engine from experiencing a leak.


Always do the easiest things first. That would indicate the hoses, manifold, head unit, and vacuum motor. If that does not fix it, then it is time to go inside the ductwork.
 

·
Banned
Joined
·
3,437 Posts
on the passenger side of the engine intake manifold next to the fuel regulator vac port is the hvac control vac port. as was mentioned this has a check valve. lets say this was installed backwards [check valve] then this would cause HVAC control problems . replacing the heater core you may have messed up the vac line to the temp door. disconnected/pinched ..

using a vac gauge see if you get vac at the intake vac ports .
 

·
Registered
Joined
·
11,207 Posts
If the check valve is installed backwards, NONE of the heater controls would work, because it would block all vacuum from the system.
 
1 - 13 of 13 Posts
Top