1991 Q45 thermostat ????

[bigwillie]

Hello All,

I'm new to the board and was wondering could any one help me out.

I have a 1991 q45 seems like the thermostat is sticking shut . Cold one

day then out of the blue the heat will switch on ?? I bought a new

thermostat any diagrams on housing would be appreciated........

[maxnix]

Make sure it is an OEM one.

NAPA and others are known to fail early.

You will need RTV, distilled water, and some more of your chosen coolant. Good time to flush your cooling system and clean the fins of your radiator.

Search is a wonderful thing, and there is even a tutorial on it.

zerothread?id=168926

Have you read the timing chain guide Article?

Welcome to the best Infiniti Q45 resource on the internet.

[elwesso]

ahh brilliant, thanks for the diagram brian.

The Tstat only takes about 15mins to do assuming you dont have to fight hoses too much... Good to replace. if that doesntfix it (the overheating problem), you may need anew radiator.

[Q45tech]

95% of thermostats partially open and fail to create proper coolant temperature. In 16 years I've never seen an oem fail closed causing over heat.

[bigwillie]

Thanks a million the info was usefull. I changed the thermostat still no heat

Im confused its full of fluid and new waterpump what else is their ? heater core ? Its not overheating just no heat mabe its a bad switch, anyway thanks

alot maxnix,q45tech,and elwesso you guys are awsome.............

[elwesso]

wait a second, are you saying your not getting any heat, or the car is overheating... 2 COMPLETELY different things.

if the heat isnt coming on, you probably have a bad mix door...

[96Qowner]

wait a second, are you saying your not getting any heat, or the car is overheating... if the heat isnt coming on, you probably have a bad mix door...

I thought so too, at first, but he said this:

Cold one day then out of the blue the heat will switch on ??

A broken mix door wouldn't be intermittant.

[elwesso]

I thought so too, at first, but he said this:

A broken mix door wouldn't be intermittant.

the mix door isnt what fails its the arm that connects the actuator to the door... And actually, what causes that to FAIL is the door getting stuck (due to dirt or something like that).. so id say its possible that maybe somehow it wedged itself free..

[bigwillie]

Sorry for the confusion, Its Not overheating. Motor temp is fine just ice cold like the a/c is stuck on.

[qship96]

I thought the 90-93 did not have this problem due to metal rod that was replaced by plastic in 94?

[elwesso]

it could be its (the mix door) is stuck, ive never heard of a heater core failing or the valve, which is the only other things it could be.

[maxnix]

I thought the 90-93 did not have this problem due to metal rod that was replaced by plastic in 94?

The one that was repaired in situ was a 1993.

[Q45tech]

Follow the HVAC diagnostic proceedure [in your FSM] to make sure it is not in HVAC unit or a sensor first.

[DrewQ45]

Does your fan blow at all? If you press the "Econ" button and cycle the temp between highest/lowest, can you hear the the mechanism (mix door etc) shifting position in the dash? Can't picture the location without looking under the hood but you might try feeling the heater hoses where they lead into the firewall. Another possibility might be bad HVAC controller.

[elwesso]

something occurred to me... Maybe its just stuck, if so you should be able to move it from full hot to full cold a few times maybe that would help.... worth a try...

[bigwillie]

To update I screwed around with the door, not sure what I did but I

have heat since I live in Michigan its a must. Thanks everyone

for the advice this site Rocks !!!

P.S. Thinking about parting her out I will post pics soon but great motor/Trans runs smooth............

[elwesso]

Hello All,

I'm new to the board and was wondering could any one help me out.

I have a 1991 q45 seems like the thermostat is sticking shut . Cold one

day then out of the blue the heat will switch on ?? I bought a new

thermostat any diagrams on housing would be appreciated........

.where in grand rapids do you live???

[bigwillie]

S.E. side hall st. area

[Jesda]

My OEM 'stat finally failed closed after 185k. I stuck it in a boiling pot of water and it refused to budge.

On the driver side of the engine on the front, you remove the plastic covers on top (the one with the engine label on it) and you should see the big coolant hose going to the engine. That connection point is the metal thernostat housing that needs to be removed. Inside is the thermostat.