OK little mystery here: Whilst changing the timing belt, I also put on a new water pump, changed radiator hoses, heater hoses (that was fun), put in a new thermostat. So then I flushed the radiator, like the directions say on the flush: "Run car to normal operating temp, put heater on high, run for 10 more minutes.." But there was no heat coming out the vents. I checked the radiator hoses - they were hot and full of water, the supply heater hose was also hot.
Any ideas? Thanks.

You verified hot water in the small hoses to/from the heater at the firewall.
So I'd suspect a bad heater valve (however they usually fail open, not closed) or possibly a blocked heater core. Or maybe a previous owner/mechanic did a bypass on the cabin side of the firewall, preventing any coolant from getting to the heater core. Heater core replacement is not fun so that could inspire a bypass if core was leaking.

If you're new to 240s, make sure you're using the temperature slider at lower left area of console to control heat. The rotating knob is fan speeds only.

Did you have working heat before doing the work on the cooling system?
I'll presume not, as I wouldn't expect that you'd accidentally disable the heat in doing the work you did.
--
Sven: '89 245 NA, 951 ECU, expanded air dam, forward belly pan reaches oem belly pan, airbox heater upgraded, E-fan, 205/65-15 at 50 psi, IPD sways, no a/c-p/s belt, E-Codes, amber front corner reflectors, aero front face, quad horns, tach, small clock.

Well either there wasn't a problem and I didn't let the car run long enough (15 minutes should get me hot air in FL, even in March) or it (whatever it was) started working again. I had heat before, not that I use it alot, probably in the mornings for a few minutes in Jan/Feb (sutle dig there). So I finished the flush procedure, put new coolant in and went for a spin - and got heat!
Possibilities:
1) The flush/straight water mix and low load on the engine doesn't create enough heat in the system? I dont' think so.
2) The heater valve got unstuck after soaking in a little ethelyne glycol. This seems likely as I had the car up on blocks for several weeks with the cooland drained. Probably.

Now just check your coolant level, prolly a little low after burping the heater core. :-)

Did you install the new T-stat with the jiggly air bleeder thingy on top?

-Ryan
--

Athens, Ohio
1987 245 DL 314k, Dog-mobile
1990 245 DL 134k M47, E-codes, GT Sway Bars
1991 745 GL 300k, Regina, 23/21mm Turbo Sway Bars
Buckeye Volvo Club

A complete drain will often result in a air lock at the highest point (heater core) on refilling. It takes time (motion helps) to bleed this air out and let the hot coolant flow through. Same principle as vapor lock in a fuel system or air in brake lines.

Same thing happened to me, sounds like an airlock.

Ron
93 245
near Brantford, ON, Can

As Ronald and Lew have stated--the problem you had was an air pocket in the heater system. Volvos are pretty good about forcing the air out on their own eventually. Some cars like Renaults have little bleeder valves in the cooling system. Cracking a return hose from heater at idle speed will usually purge the air.

Must have been the burp, works ok, yes the little vent hole on the thermostat is on top, thanks for all the feedback!