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Ricardo Hohl
Ricardo Hohl, ASE Master Certified Tech
Category: Car
Satisfied Customers: 4210
Experience:  Automotive instructor at Porter and Chester institute
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no heat even after new thermastat radiator heater core fan

This answer was rated:

no heat even after new thermastat radiator heater core fan works but no heat

Is this the 5.0l? Look at the picture below and see if you have that valve #1. If so, make sure if there is any vacuum hoses or electrical wires going to it they are hooked up. Feel both heater hoses, #'s 4 and 6, they should both be hot. Let me know if both hoses are hot and if anything was off that valve.


If everything checks out, it may just be a faulty valve.

They list one here for $34.76, Cruiser&Year=1986&MakeCode=O&ModelCode=B&CatalogCode=32W&mCode=3BP35&majorIndexID=08&minorIndexID=MB08-002&SortKey=58

Copy and paste that link in browser.

Customer: replied 4 years ago.

i am waiting for motor to warm up how ever looks like something not rigft with that valve hole in top of valve has nothing hooked to it and another short hose heads toward front of motor but not hooked to anything im going out now to check if hoses are hot ill be back with you in 5 min


Customer: replied 4 years ago.
Relist: Incomplete answer.
hose from back of block is hot hose from water pump is cool
Hi, let me see if i can help you with this problem , if the hoe is hot from the water pump to the heater valve but from the valve to the heater core is cold then you need a heater control valve or the vacuum on the back of the valve is missing or is leaking vacuum.
Customer: replied 4 years ago.

it is just opposite of what you said in other words hose from water pump is cold. other hose is hot.

ok, water pump circulates water to the heater core but does not move because the heater valve is not opening for water to flow. either wayif the hot water is not flowing there will not be heat this is because the heater valve is not opening..... there is a vacuum attach to the back of that valve can you see if the vacuum hose is in place and if it has vacuum on it.
Customer: replied 4 years ago.

refering to the picture or diagram i was sent heater valve is #1 and it shows hose #6 going to it but in my case it does not. it comes out of fire wall or i guess heater core straight to rear of the block. and nothing is hooked to that place where digram shoes hose 6 going to #1 (valve) also there is a small hose out of valve that is capt off with a screw hose #6 is hot hose#4 is cold

ok then you are missing the valve thats why . this means some one bypass the heater valve posibly because it was leaking. and capt off the vacuum hose, you will need to get that valve.
Ricardo Hohl, ASE Master Certified Tech
Category: Car
Satisfied Customers: 4210
Experience: Automotive instructor at Porter and Chester institute
Ricardo Hohl and 14 other Car Specialists are ready to help you
the flow on this cooling system is from the water pump to through the headand in to the cilinders water jackets and back to the top of the head, then in to the intake manifold, at this point is verry hot going to through the heater valve and in to the heater core, from there it goes out back to the water pump cold because the blower motor inside the heater box removes the heat and puts it in to the inside cavin.
Customer: replied 4 years ago.

put the new valve on no change heater still blows cold. an older retired GM mechanic tells me it might be a bad head gasket. all i know for sure is this thing is making me go nuts and broke at the same time. any other ideas?