Just put a car (260K miles) on the road after it had been sitting 2+ years (in a dry & heated garage).

Had to replace various bushings, belts, voltage regulator etc - the usual after a car's been sitting.

The heat is lukewarm at best. I replaced the thermostat; the coolant is clean; heater valve seems to move freely; it warms up quickly & temp gauge needle stays in the middle. On a cold day - say high 20s F - the defroster air barely unfogs the windshield and the air through the vests just never gets hot.

I've never had this problem w/ a 240. I'm guessing a clogged heater core or a stick/ bad/ clogged heater valve. Someone used black silicone around the thermostat: It looks like he/ she coated both sides with ~ 1/4 tube of silicone (to compensate for a brittle rubber gasket?) and I wouldn't be amazed if pieces of that found their way into the heater core.

Has anyone had this problem and fixed it? I don't want to run flush through it as I've seen that create leaks. I could try to backflush it but that's not a fun job this time of year.

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240s: 2 drivers and some parts cars

I had a problem with a partially obtructed heater core in my 740. You can feel the temperature of the hoses going into the firewall. If one is hot and the other not-so with not much heat output , then the core is partially blocked.

What I did was to clamp the two hoses at the firewall, remove them, and reverse flushed the heater core (input the garden hose where the colder hose was)with a garden hose. I used a nipple attachement on the garden hose and clamped another hose from it to the core, then another from the core to a bucket to collect the flushed material. Heat was a world of difference after that.
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Paul NW Indiana '89 744 Turbo 145K/ '90 745 turbo 127K

Thank you Paul, Matt & Dave for the prompt replies.

Pls note that I did replace the thermostat almost 1st thing. I did so because it's easy, I have spares, seemed like a good idea to check it out, and the temp gauge had some variation eg. it would run just under the middle for a while and then drop down until it was ~1/2 way between the middle and bottom.

The gauge is now steady and so I think either the old thermostat was bad (rare in my experience) of some of the silicone pieces were sticking in it - there was a LOT of silicone.

I think I will try a backflush 1st after checking the output hose. If it fails or makes it worse nothing lost really. I dread doing the core itself.

Thanks again all.
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240s: 2 drivers and some parts cars

We'll assume the vents are working properly...? That is to say, air comes out of the vents as requested, just not warm air?

And you are topped up on coolant..?

If so, I'd start by replacing the thermostat. Absolutely start with the thermostat.. I could see one going bad/stuck open in a car that's been sitting for two years...

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-Matt I ♥ my ♂

I'll have to disagree with Matt B regarding where to look first---if the thermostat was the problem it's not likely your gauge would read normal operating temp. I'd look to feel the heater hoses--looking for one side to be hot--the other cold or much cooler. If that's the case I'd then check the heater valve to be sure the cable is opening it. If the cable is doing it's job the likelihood is the core is clogged--by silicone or sediment. I've had one Volvo (265-V8 Oldsmobile conversion)) that did clog the core--the body was nothing to write home about so I changed the core by way of the "chainsaw" method and found a core probably twice the weight of an unclogged one. If you wait to backflush the core it's only going get harder - weather wise. -- Dave