1974 Coupe deville questions

[Ville]

Heater hose switch closed or minimum, engine temp was little bit lower but no big effect no matter what.

[Ville]

I checked air pump. I removed hose between check valve and pump. In idle pump gived continuous air but check valve gived liiitle back pressure on finger when i tested. Little noise flaflaflafla too. Normal? I forgot try on higher rpm.

[TJ Hopland]

Its normal to have air out of the pump at idle, the only time it does not pump air is deceleration.  I think will do its thing not driving.  I think you can raise the RPM and then let it come down fairly quickly the dirverter valve should operate and not pump air to the heads for the few seconds the engine is decelerating.   Its been a long time since I have worked on a non computer car that had this system working so I could be wrong about being able to test it not under load. 

There should be no flow from the crossover pipe.   If there is flow the check valve is bad.   The valve is there to keep exhaust from backflowing into the AIR system.  The exhaust tends to damage the system.  I'm not sure about where you are or even in the USA anymore but those valves used to be somewhat universal and easy to find.   The same basic valve fit most American cars in the 70's and 80's when the AIR (smog) pumps were commonly used.     

[Ville]

Thanks i will check that.

I dont get anything else than take coolant and thermostat off again today and just wonder why it wont goes normal temp.

[Ville]

Air pump hose off and backfire was gone 

I dont get pretty easy new part. Does it matter if i but plugn valve and turn air hose to blow free?

[Ville]

I didnt  found nothing bad to thermostat. It was closed position when I pulled it off. Now there is old thermostat and lets try with that.

[Ville]

Nothing changed.

Does someone had temp gauge on this type engine? Will it show real temp in that spot?

[Ville]

Couple problems more:

Headlight switch will not always work. Park lamps position works always but headlight no. It does it couple times per day, works ir no. I overhauled that switch month ago and it worked well a while but not anymore. There was only old stuff inside but when I cleaned it it's like new.


Car was with on/off switch and push button start. Now I did wiring to the original ignition switch with shop manual. All works fine but warning lights were all gone. All wires are like should be. Before wired was in big sump to on/off switch and couple for start button.

[Ville]

Thermostat is ok. Gauge was faulty.

[Ville]

What is most common part to fail in guidematic? Will it be able to test with flaslight etc? I mean that eye on front grille.


Double checked wires, ground and ignition switch. No warning lights. Fuel gauge works but not trunk open.

Brake light has been dark all the tine. Bulb is ok.

[Ville]

With 16lb raditor cap and 180f thermostat, what is normal temp in idle/highway?

[Ville]

Blower works only at vent (low) and defrost (hi). What causes that?

Also heat will not come allways. Hoses are hot so problem is inside. All vacuum lines checked and control head works.

[TJ Hopland]

There is a 1 wire sensor in the corner of the head just behind the alternator.   At 120*F it grounds which then lets the blower run on speeds other than low for heating modes.   Its possible that the wire got knocked off and sometimes grounds which then lets the blower run.   

[Ville]

Thanks i check that. Relay blinks when i switch off the vent or defrost.

Does that air door under glovebox allways get always opened when temperature is max cold?

[Ville]

It was connected but not grounded. I grounded it to body and now blower works hi on auto, hi, bi level and defrost. Vent is low. Thats good. But is it now that kind speeds no matter what?