Need to flush my heater core.

[wht89reatta]

Hey there guys. I have been experiencing very little heat coming from the vents. I need to fluch me heater core but I have no idea which is the inlet and outlet. Can anyone help me figure which is which? any help is much appreciated.

[KongaMan]

Doesn't matter; flush it both ways.

[Ronnie]

Before you get your water hose out and start flushing you might want to read this. No Heat - Troubleshooting  This may not be your problem but then again, It might save you some extra work.

[DAVES89]

 Is there heat coming from anywhere?  If so it is not the heater core.

 What setting do you have it on? If there is only good flow through the defroster vent it could be the lever that directs the flow through the vents or to the floor. If it is broke you only get air at the defroster. 

 You could also remove the glove box and look at the rod that opens and closes the temperature door. 

 The other thing you should check would be to remove the blower fan and look at the evaporator. If it is all clogged up that is most of your issue.

 Not many people have come on the forum with bad heater cores.

 I see Ronnie beat me and he also posted pictures. That will help more.

Edited December 30, 2017 by DAVES89 (see edit history)

[wht89reatta]

Im pretty sure I have a head gasket issue so I have to fill my coolant on the regular but even when it has coolant on max heat it still on puts out tepid air. I need to flush out the heater core as yesterday my thermostat froze causing my heater hose to burst, so I figured I'd do that before I put on new hoses. I just need my car to last a few more months until I can park her for a proper rebuild.

[wht89reatta]

Also the blend door is working fine and I'm only getting tepid air everywhere. The temperature control seems to be working fine as it switches from cold to room temperature when I move it from max cool to max heat.

[Ronnie]

What is the engine temperature when the engine has warmed up to operating temperature?  If you have a blown head gasket that is allowing coolant to escape you should be seeing lots of steam coming out the exhaust pipe when the engine is fully warmed up. Or you should see coolant leaking out on the ground.

[wht89reatta]

There is no coolant on the ground. It usually runs around 180 to 189 when warmed up. Im fairly sure it's burning coolant as there are no visible leaks yet every couple of weeks I'll have to add coolant.

[fordrodsteven]

low coolant or any air in the system will cause a "no or minimal heat" condition.....just sayin'

Edited December 31, 2017 by fordrodsteven (see edit history)

[DAVES89]

It could be your water pump going bad or the little coolant hose above the water pump or the intake manifold gasket. Not many people have blown head gaskets. However if you have freezing at the thermostat all bets are off. 

 If it were my car I would start at the hoses, thermostat, and water pump. Then if you are still adding anti freeze look at the gaskets [intake or head].

 One last thing, no leaking on the ground tells me that you are "burning off" antifreeze which makes me think it is either the intake manifold gasket or the little hose above the water pump. 

[dship]

Very unlikely a 3800 would experience a blown head gasket (a Caddy early produced Northstar is way more likely!).  Blown head gaskets lead to anti-freeze mixing in with the car's oil.  

[fordrodsteven]

7 minutes ago, DShip said:

Very unlikely a 3800 would experience a blown head gasket (a Caddy early produced Northstar is way more likely!).  Blown head gaskets lead to anti-freeze mixing in with the car's oil.  

Or oil in the radiator (if the oil is under pressure wherever the leak may be)

[Ronnie]

If there isn't any oil mixing with water, a bad intake gaskets is a good possibility for the coolant loss.

[2seater]

Typical spot for intake manifold coolant leak is the drivers side rear corner. The intake manifold erodes around the coolant port. GM even recommends a leak sealant as normal in the FSM. The eroded area can be fixed with JB Weld or use a new style solid style intake gasket that doesn't have the imprinted o-ring. Agree a head gasket blown would be unusual unless severely overheated.

I am assuming "thermostat froze" means it stuck closed not actually froze due to temperature?

[wht89reatta]

It was most likely stuck closed but opened up after I let it sit for a while. There is no oil in the radiator so it is most likely an intake gasket issue. I've been out of the auto industry for some time now so it slipped my mind that that's what it could be. Thanks for the advice guys.

[retiredmechanic74]

Flushing the heater core and radiator at least every two years is a good idea whether you have good heat or not. The anti-freeze used in todays engines are prone to breaking down do to the high temperatures from the engine. The heater core inlet feed is generally the hose closest to the waterpump and enter the core at the top. Follow the hose to the core and remove the hose and install a drain hose to that pipe then take the male end of an old garden hose install it to the other pipe  on the core (this will back flush the core) and install water supply.  After you flush the core leave it disconnected. Clamp off the hose coming from the waterpump and install the gardenhose  (male end) in place of the other heater hose coming from the engine and install the water supply do not turn on the water supply.(this will back flush the engine). Remove the thermostat, put the housing back on  put the flushing chemicals  in the radiator and run the engine (with the cap off) until  hot. Now comes the tricky part leave the engine running and slowly turn the water supply on to a "Very" slow rate (cap still off) and run until the engine goes from hot to ( you may have to adjust the water supply ) warm to the touch then turn up the hose and run till water is clear. Drain reinstall thermostat and fill with proper amount of anti-freeze. NOTE Loss of coolant can also be from a bad radiator cap.  

Edited January 2, 2018 by retired mechanic74 (see edit history)