better_sideways

Hello

Just reacently got a 90 new yorker 5th ave. Pretty with only 47,xxx miles.
everything looked good and worked so bought it,(for my girlfriend) as she liked it. Either way about a week later, started it up in morning and let run for usual 15-20min as its cold here in WI right now. Was gonna give her a ride to work so can come change oil and check everything over started going and turned heat on and there was nothing and was blowing cold air, so first i changed the thermostat, that didnt solve anything. The radiator wasnt the best looking, and water pump was kinda noisey but not leaking or anything, so decided to just get new radiator and water pump, changed both of those and still no heat, both in and out tubes on the radiator and heater core both get hot and can feel fluid running thru them. It has digital everything on top of it. So what could be the problem??

Any input would be greatly appreciated, as its aproaching coldest part of year.

Great timing huh. lol

Gorts 5th

Welcome.
i'm assuming the car is a M-body or rear wheel drive.
i know the problem i have the same issue. Though i live in florida and for me heat is not that big a deal.
There is a servo motor on the air box up under the dash it's on top of the box, from what i have learned these motors can fail for various reason's including..
-burnt motor non repairable
-dirty contacts/corrosion dirt grease repairable sometimes,
-derbies, leaf's , dirt pulled into the air box get jammed into the mix door and it wont move.
All the fixes for this issue dictate the removal of the air box. including the donor car. "i've never found new replacement part's"....
All accept this one...... a dirty or burnt servo relay on the back of the climate control panel in the dash.
-also there is a resistor up under the passenger side dash just follow the air tube's...
The for-ever fix is to find a manual mix climate panel with the cable and linkage with the mix door and swap the whole system, say... out of a diplomat or maybe a aspen with same climate MIX options.
Hope this help's keep me updated.

better_sideways

It would be a m-body style, Its front wheel drive and has the 3.3L.

so would the mix door be located in air box?

and i pulled the climate control panel out and only had 1 plug with all the wires in the back didnt see any servo relay, would be located somewhere else?

the resistor unde passger dash, is that for the servo motor? or ?

Let me know & Thanks much for replying, Much appreciated, Cause i would hate to take to the shop for somthing so simple, that i can do myself.

Thanks Again!

Gorts 5th

oh
front wheel drive model, i'm not familiar with it. i have a 86 5th ave M-body.

better_sideways

so i just noticed now the upper radiator hose doesnt feel like has any pressure? it gets hot after driving around but no pressure. could be a faulty thermostat? or air in colling system?

Also because i replaced the radiator (original copper 1) to a new alum one, would i have to get a new radiator cap too? could that be a problem for no heat or pressure in upper radiator hose?

any input would be great.

Chryco Psycho

a bad rad cap will not allow it to pressure up but if the thermostat is not opening it should be very hot on the temp gauge , conversly if it is not closing the engine will never warm up so it coul dbe bad . What about the heater hoses are they getting hot , is there a sticky control valve not allowing water flow in & out of the heater core ?

LadyKrosehiggins1971

LadyKrosehiggins1971

I had same issue no heat, new thermostat no heat. I notice the coolant tank when hot linked, Put on new universal tank new hose and clamps. Which I notice where the hose to the radiator on top didn't have a clamp so I put one there with new hose. After replacing it I have great heat. I hope this helps you, it was easy cheap to do.