2002 No Heat

My wife's 2002 Passat has intermittent and usually no heat. (Second winter now). The dealer sez the heater core is blocked and wants to replace it. This of course costs $1300. I think they're full of s***. Temp gauge is in the normal ops range, no overheating. No evidence of a kinked hose. Two people have suggested draining down the coolant to see if the core is air locked. (The dealer sez they back flushed the the core). I also was thinking about checking the hoses etc. with my laser heat detector to see if any one is hotter or cooler than another. I guess the real question here is, are there any air or electrical dampers or valves I can check? Where are they physically located, if so? Does Passat have cooling system quirks I should be aware of?

Thanks in advance.

Today I worked on this issue more. I have got heat! Here's what I did. I took the heater hoses off the core. Since the engine was up to temp, I was expecting lots of fluid to escape under good pressure. There was little pressure and little volume. I took unregulated air pressure (175 lbs) off the compressor and blew the snot out of the core. VERY little junk came out. I did both tubes. Nothing.Took it apart again. On the drivers side there is a fitting at the rear of the engine, it goes from rubber hose to a plastic 90 ell to the metal tubing that goes into the bulkhead at the oil filter. Blew the snot out of that. Nothing. Ran the car with both heater hoses disconnected. Now, I should have been pumping coolant like crazy. Nothing. Blew thru the hoses until coolant gushed out. Put it all back together and it works. The blockage was somewhere in the block, NOT in the core. After that I could blow thru the system by mouth. Topped off the system and it works great. As I test drove, I noted at speed, the air temp at the vents was @150 deg. F. When I stopped I noted the temp rolled off to @120 deg. F. (Used an IR thermometer). Now I wonder if the expansion tank cap is not operating at the proper pressure. I don't have the spec. for it and I may just replace it as a matter of course. I opened the cap at full operating temp. and got very little hiss, making me think the closed system pressure might be too low.