Heater not working, just can feel some heat. Flushed heater core, changed thermostat and radiator cap. When flushed had flow thru heater core, with enging running have little if any flow thru core. Passenger side core hose is hot, driver side core hose is only warm. When remove driver side while engine running got a pencil steam out of core, may have been fluid trapped in core? Suspect have a valve not opening? Any ideas where to look or what should do next. Not sure where valve is? Is it operated by vacum?

Thanks

 

Hi oldman,
There is no valve in the heater system. Coolant always flows thru the heater core regardless of temp setting. How does the flow into the heater core look? The hose on the passenger side is inlet. Have you tried pulling that hose off from the core to see if you are getting good flow to the core? If not, very slight possibilty that there is a restriction in block but that would be very unusual.
More likely that the heater core is restricted. Both hoses should be fairly similar in temp with the drivers side or outlet being only 10'F or so cooler. When flushing with water, if you were using a garden hose there is huge difference in pressure/volume coming out of the hose then is provided by your engine water pump to the core inlet.

 

Thanks for information, I have flushed core both ways with garden hose, saw no difference in flow. I will remove passenger side hose from core and see if have flow. If I have flow does this mean I need to replace heater core, if so I presume have to remove part of dash area. It may have to sit a few days it is suppose to get cold the next few days!
Thanks, Oldman

 

If you have good flow from the passenger side hose coming out of the engine then should point to the restriction being in the heater core itself. Am not a 100% on this since has been a long time dealing with heater core on 91 but am pretty sure the entire heater box needs to be removed from vehicle in order to access and replace the core. Only way to get the box out is complete removal of dashboard[:@]. Do a little digging but that is best I can remember and shop manual indicates the same.
If you do determine that the core is source of the restriction, you might give this a try. Have done this 1/2 dozen times including on my own 91 323 and all but once was able to increase temp output quite a bit. Temp in my own car came up from 95'f to 140'f and that sure made a nice difference.
Take both of the heater hoses off from the firewall and install two lengths of heater hose to to each core connection that are 1-2 feet long. Angle the hoses so they then aim straight up and secure with bungee or whatever. Purchase a bottle of CLR ( you know, the one you see on TV that dissolves all the minerals ) and pour into each hose untill full to top. Let sit a couple of hours if possible and then drain and flush out good in both directions. That stuff is brutal on mineral deposits and that is exactly what is clogging up the system. Best case is that you have increased heat output. Worse case is that it does not work and /or did work enough to clean out an area that was leaking and now is again. In that case you will still need to replace the core.

 

Soon as weather warms up will check passenger side flow and clean core thanks for info. will let you know how turns out.