gbmarc

OK, so I got the pinch bolt out. Air hammer was useless. I cut it off thru the split about 1" from the head and pulled the head part out, then tightened the nut on the other end and drew it out. It's weird. Mine wasn't rusted. It's simply the structure and configuration that jams it in. I would turn the nut a couple of half turns and there would be a big "crack" as the seized bolt shifted a fraction.

So, now with a new driveshaft and new front rotors and pads, the brake judder has gone and it runs smoothly. Interesting, all though the CV boot was not split, the joint must have still gone bad inside. Never had that happen before.

gbmarc

OK, so now I'm moving on to the no heat problem. So far I have: Both pipes on the engine side of the control valve are hot. All pipes from the control valve to the cores are cold.
I feel no solenoid or anything going on with the fancy valve thingy. The two round towers are silent and cold. Is there anything I'm missing? Or should I mortgage my house to buy a new control valve?

Redd

gb-
" Air hammer was useless."

Of course! It is good German engineering, a proper metric air hammer is required. Here now, you go to the metric window on the Snap-On van and tell the good man I sent you for proper metric air hammer.
(WEG)

gbmarc

Had an inspiration while at church this morning (it happens sometimes!): "I wonder if there's a fuse for this heater control valve thingy?" Turns out, it's #7 in the yellow bank. And mine was blown! I was all excited. I popped in a new fuse, cranked up the heating, popped the hood and swore I could feel the valve towers clicking faintly. Went back inside and . . . . no heat at all.
So back to square one, only maybe the fuse blew because these valves are on the way out. I checked the new fuse 30 minutes later and it was still good. Has anyone taken this valve apart?
Mark

silverd2

Yes, a past poster here did, but the photos have been since deleted. His failed because it was full of the choking corrosive brown sludge that is created when mixing ANY other coolant with the correct pink/red G-12. Even after a drain and refill, without a full chemical flush, the sludge will remain hidden and reproduce even more brown sludge when new G-12 is put in. It can clog the valve unit and even a heater core, plus can eat up rubber and plastic fittings...It's as bad (and worse) than EVER using coolant stop leak, which easily clog a heater core...both require chemical flush and back-flushing the cores.

gbmarc

What does a working valve feel/sound like? Can you feel the solenoid moving back and forward if you hold the cylindrical towers?
It looks like the tower case could be taken off in situ. I really don't want to remove the brake booster and bleed all the brakes etc just to get at the heater valve, especially as I'm not 100% certain the valve is the problem.
. . .but winter is coming!

nyrobbie77

I was replaced my after-run pump 3 years ago, here is the link SilverD2 is referring to: 97 a8 no heat

I will have to see if I still have the pics of the dismantled pump on my computer at home.

replacing it was not difficult. You will need to remove the brake master cylinder to remove it. you DO NOT need to hack up the air duct work that another user in my thread did to do the work. It shouldn't take you much more than an afternoon. IIRC I paid $100 shipped for the unit. OEM is 10x's more than that.

nyrobbie77

the solenoids will buzz and vibrate when working.

there is a real quick way to determine if it is plugged. first you may notice that the top heater hose is not hot and the lower one is (lower is from engine to pump, top is pump back to engine). Then to check if it is flowing, simply disconnect both hoses at the firewall and spray water into the pump. I could barely get any water to go in, it would just spray back out. with the new-to-me pump water would flow freely thru the pump and into the heater cores and back out of the pump.

twentysevenlitres

Just to note, the after run pump shouldn't restrict flow under normal circumstances, as it is dormant 99.9% of the time.
It is there to provide heat to the heater core from a hot engine when it has been shut off (by pressing 'Rest' on the climate control IIRC).
The rest of the time flow is provided by the main engine water pump as per nearly every other car on the planet made in the last 40 years!

I would bet on it being blocked. Maybe at the after run pump, maybe at the heater cores.
Also bear in mind that there are two heater cores in a D2 (right and left) and that the junction point for the hoses is at the after run pump housing.

Redd

gb-
Do bear in mind that it is most unusual for a fuse to just blow for no reason. If you can't find something wrong, pull the fuse and use a multimeter with a 10A setting to bridge the fuse contacts. (Assuming it was a 10A or less fuse, next step up is a 20A rated meter.) That will show you how much power the circuit is pulling. If there is a problem and the circuit is pulling even half of the fuse rating? That could mean the motor is having a problem and IS going to burn out at some less convenient time, like midwinter.

Very rare that these ATF/ATO type fuses burn out without good reason.