am muscl

i have a 86 z28 and it sat for 2 years only being started once a month. it runs about 190 and ive flushed the heater core and no blockage but the only time the heater throws heat is when im reving it up. ive ran it with the rad cap off and filled it until all the air was out. any other ideas im at a loss

85irocinjected

Your heater hoses could have a blockage or the heater core it self is stopped up. You can pull the heater hoses off the engine side and try to flush out the core but a lot of time that ends up cleaning out all the junk that's stopping it from leaking to begin with. But you should give it a try and if you get your heat back you know the heater core was clogged. Also keep an eye out for leaks on the floor board though, I case it does start leaking.

am muscl

i already pulled the hoses at the engine and hooked a garden hose up to one and there is no blockage it flows perfect thru the heater core

MAC_87

iTrader: (3)

Maybe it has to do with the flap that changes from cold to hot air, thats down by the core.
perhaps its not functioning correctly.

gp90gta

iTrader: (1)

Best way to check is let the car run with the heat on, grab both hoses to see is there hot, if they are that means coolant is going through fine and there is heat at the heater core, at this piont you need to check the blend door to see if it is working, also remember that you need vaccum at the climate control.

t-top havoc

iTrader: (3)

Check the radiator & over flow levels.
Top them off if low, let it warm up to temp with the rad cap off, top off if needed.
If the levels are good, warm it up to temp with the rad cap off, top off if needed.

If the rad is low, there isn't enough coolant // anti freeze to supply the heater core.
If the level is good, maybe an air pocket in the system?

am muscl

i have the heater control switched to hot under the dash. and ive let it run for an hour without the rad cap on it should have cycled enuf and its full. the hoses are only hot when i rev it up. its like the engine isnt pumping the water thru the hoses until its revved

MAC_87

iTrader: (3)

sounds like ur water pump is going out :O

am muscl

i kinda thought that too but normally if u can see a good flow with the rad cap off thats good and it has great flow in the rad but ya im gonna try changing that

85irocinjected

How are the radiator hoses? Are they both hot? If not then your thermostat could be restricting the coolant flow also. But just cause your temp gauge shows good that does not mean your getting proper flow through the engine.

Had a vehicle with a bad water pump (shaft snapped off) but the temp gauge would read fine cause it was near the top of the engine while the bottom was overheating. Needless to say that engine went up in smoke. Or actually melted down into a solid boat anchor..

am muscl

im gettin good flow. does the heater core get water from the pump or from the intake

ex-x-fire

From the intake, remove that hose & have someone start the engine, it should pour out like a garden hose.
Waterpump impellar might be erroded enough to cause no heat at idle, remove the pump & its cover to inspect it.

am muscl

im going to put a new water pump in it this week and i hope that fixes it

Davidgou

iTrader: (2)

If you're gonna replace your water pump anyways, might as well replace the thermostat too, it's a cheap fix and a very important one too.

am muscl

ya i changed that 2 weeks ago

Davidgou

iTrader: (2)

Oh sorry, I must have missed before. I hope the new water pump solves your problem man.

am muscl

thanx i appreciate all the help ive gotten

camarosrock1989

iTrader: (1)

Hows the heater control Valve? also could be your heat control switch in the dash. Heater blower motor, if it is even weak, it won't work.
Just a though.

am muscl

its switched to heat manually. that was one of my first things i fixed. the cable was broke

am muscl

changed the water pump and still only heats if im revving it up. the heat valve inside is switched to heat, its full of water. as soon as i rev it i hav heat and then i let off and it cools down. im pulling my hair out wth is the problem

ex-x-fire

Can you take a picture of the heater hoses & where they hook up.
Your not running underdrive pulleys, are you?

gp90gta

iTrader: (1)

The heater control valve is not in the car, its on the hose that feeds coolant to the heater core, it should have a vacuum hose going to it. When you said the hoses get hot only when you rev the engine, what hoses are you talking about? The hoses going to the heater core are what feed coolant into the core, which is how you get heat in the car, notice I said in the car and not out of the vents.

The system works like this (on most cars also). The engine coolant get hot, the water pump circulates the coolant (must be full and air bled out of the system). At this point to get heat in the car we have a feed and return hose, plus most cars have a heater control valve ( like a on off switch that blocks coolant from flowing), most heater valve work by cable or vacuum, some on newer cars are electric and some cars don't have one at all. So when you slide or turn your heater control switch from cold to hot, a cable or vacuum truns the valve on to let coolant into the heater core. Now the core is hot but that does not mean you have heat out of the vents yet, all cars have a blend door in the heater box (the heater box is in the car under the dash), what is does is blend hot air with cold air, now this door is also controlled by a cable or vacuum dash pod valve or an electic motor, either way is the door is stuck on cold you will not have heat in the car, weather or not the heater core is hot.


So as I said before, let the engine get hot, leave it at idle in park, turn on the heat and check the two hoses feeding the core, if there both hot you have heat in the core, if not check the heater control valve and make sure its working ( you said that you car idles 190* so the coolant is hot, which means and this is as long as the engine coolant is full and no air in the system, your water pump is fine.) Now if you have no heater control valve and you only get heat when you rev the engine, then there is air in the system, the best way to get all the air out is jack up the front of the car as high as you can get it, block the wheels and put stands under the car, fill as much coolant as you can with the engine off, start and hold the idle at 3000rpm (best to have a helper here) keep checking coolant level add until full, 10min should be more then enough to get the air out, now put that cap back on and check those hoses again.

am muscl

ok so my blend door is switched to hot. mine does not have a heat control valve under the hood. my heater hoses go straight from the engine to the firewall. when i put my waterpump on i had the car up on my car ramps so my front end was up in the air. when i filled the antifreeze i ran the car for 20+ minutes with the rad cap off so the air shud have been out. and when reving the car i get plenty of heat inside as soon as i let it idle the heater blows cold. at idle the hose going into the heater core is hot, the return is not. when im reving it both hoses are hot

am muscl

no im not running underdrive pulleys

gp90gta

iTrader: (1)

Okay so the feed to core is the hose that comes from the intake manifold, if its hot then the your water pump is sending coolant to the heater core, at this point the lower hose should be hot if you have no heater control valve, so I would do two things, 1 take off the hoses and run a lawn hose to the top but don't use to much pressure, if it flow freely then the core should be fine, if your using a lot of pressure to get the water through the core it is most likely cloged, 2 if it is fine then what I would do next is hook up the feed hose to the core and run the engine at idle if coolant flows out then check the return hose, it should run directly to the radiator.

ex-x-fire

The intake manifold hose should feed the heater core, the return hose will either go to the water pump or the radiator side tank. Everything behind the water pump is under the water pumps pressure & should be hot, the hose on the top of the pump is not a feed hose, its a return hose.

am muscl

i thought the one from the intake was the one that feeds the core and then my other one goes to my water pump

gp90gta

iTrader: (1)

Is your car TBI, Carb or TPI?

Yeah sorry I need to edit my posts, I mean intake for the feed.

Also there is one other thing to note, there are two types of water pumps for our cars, one is v-belt and the other is for the serpentine belt which is reverse flow.

am muscl

its a carb

am muscl

i pulled both heater core hoses off at the engine and laid one down and and held the other up and i can pour water in and it runs out the other one. i did that both ways and it worked.

ex-x-fire

With the hoses off, briefly start the engine, you should see coolant pour out of the intake connection.

am muscl

i finally got a chance to try that and yes as soon as i start it coolant flows out of the hose from the intake. is there any vacuum that runs the heater in the dash at all. like i said as soon as i rev it up i have heat til i let off

mantaguy

iTrader: (5)

Yes their is a vacuum line that operates the HVAC,IT opens and closes the doors that give you defrost, heat and air,but that don't operate the the heat.

91camarosRS

iTrader: (5)

x2 on checking the heater control valve and your vac lines

am muscl

the hot/cold is mechanical and thats on hot. im just at a loss this makes no sense

ex-x-fire

I'd try to find somebody w/ an coolant airlift system, this is a tool that hooks to the radiator & sucks out all the air while filling the system w/ coolant.
Another thing you can try is get it hot, rev the engine while filling the system, the level should drop when the t stat opens, keep filling & install a new cap. Do this on level ground.

am muscl

ive tried reving the engine and filling it when the tstat opens. wasnt any change, i will have to try theairlift