Cold Start Waxstat
 

I've had to leave my cold start lever cable tied in the advance position all winter because I can't find a good waxstat. Well, now I've had enough of trying to find a good S/H one or any other "cheap fix" so I'm going to bite the bullet and pay the £80 odd that Volvo wants and hope it fixes it! :( I really don't want my car running so advanced for any longer!!

Before I do, does anyone have any other suggestions? I've tried a manual cable but the spring on the pump is so strong I couldn't get it to work.


I have now have 3 waxstat-ends of the cold start device, and 2 spring-ends. I was thinking I had some springs missing, but no, they are both the same.

I have put all 3 waxstat ends in a pan on the hob and let them all sit at ~100C for 15-20 minutes. I would expect to see them 'extend', but the only thing that happened is one of them extended about 2mm. But whereas when it was cold, it was very stiff and couldn't be pushed back in, now it was hot you could easily push it inwards (which would be the cold, advanced position).
http://i103.photobucket.com/albums/m...o/IMAG0166.jpg


I even tried putting the while unit together, leaving the correct gap in the middle for the IP bracket it fixes to on the car, and put a spring on the end, which would pull the cable 'out' - which is what the advance lever is trying to do on the pump. ...but it didn't move AT ALL...
http://i103.photobucket.com/albums/m...o/IMAG0167.jpg


So... am I just very unlucky and have gathered 3 waxstats that are all faulty? Were they that bad a design?

Yes they are faulty. The pistons should extend far further than 2mm, and nearly impossible to push back in until cooled to ambient.

Bad design? Probably not a bad use of technology of its day, but one could imagine a better design (better for the overall long-term health of the engine) using the opposite orientation: cold-start lever normally held in non-advanced position when thermostatic actuator has failed, instead of failing to the advanced timing position.

The brass actuator is held in by a collar which unscrews from the housing as you can guess from the threads. Inside the brass actuator is a small reservoir of hydraulic (brake) fluid (or similar) that when heated, actuates the highly-polished piston which slides in the brass bore, sealed by a o-ring. Life expectancy dependent on manufacturing tolerances, and corrosion or damage to the piston which could tear up the bore/seal. Severe overheating could also probably damage it.

It appears to be soldered together, not very user friendly for DIY reconditioning.

Where did you try fastening the manual cable and what type of cable did you use? I have one from a lawnmower that I have set aside to use when the actuator on mine fails.

Right, they are definitely faulty then - like I say when they get warm, they don't extend (apart from the one 2mm) but they actually get easier to push in/out.

The only manual cable I had was a bonnet release from a 940 B230FB. I tried to mount it several different ways. I think I finally found some way to mount it successfully, but on trying to activate it, all I did was pull the lever off the end of the cable in the car - that's the point I gave up (and said a few choice words).

I did find this yesterday though:

http://seekpart24.com/bosch/thermost...ent-1467202302

Over half the price of getting one from Volvo, and that's taking into account postage to UK. Sounds bit odd to me, but for that price I'll give it a go...

Theoretically the CS lever is easier to activate when the IP is rotating, so the key might be to pull the cable while cranking. Anyway, that Bosch P/N looks correct, once you get it installed it should work great! Folks in the US will be curious to see if you get the part in a timely manner; forum member Volvoist mentioned in a recent post that he just recieved the last few available here, both from Volvo and Bosch.

Yes, I had heard that it's easier to pull once the engine is rotating. Unfortunately without drilling new holes I could only pass the cable through to the passenger side, so pulling as I turn the key wasn't an option.

Well, I have had an email this morning confirming despatch and I have a tracking number, so fingers crossed! I've had the car for a year now with this thing broken - can't wait to get it fixed!

oh wow at seekparts24 is available ? Great... :cool:

Right, well the good news is that I received it (after fun dnad games with UPS) and it looks like the right part!

Although, in the packet looked fully extended. I opened the packet an the pin fell out:
http://i103.photobucket.com/albums/m...IMAG0173-1.jpg

It seems to just "sit" in there, so I thought ok, not a problem, nothing has leaked out.

However, when I push it in, it does go in a fair way, but then springs back out when I let go and sits like that:
http://i103.photobucket.com/albums/m...IMAG0175-1.jpg

Is that normal? It feels almost like there is air trapped in it springing it back out. Will be be ok as it's under a strong pressure from the spring? I can push it down with finger pressure as below:
http://i103.photobucket.com/albums/m...IMAG0176-1.jpg

I had one like that; the air eventually worked its way out. Might present a few days of inconsistent cold start behavior before you can dial it in. Keep the pin and cylinder clean when installing.

Adjust (when hot) the slack at the end of the cable so that it is slightly under tension. If the rather heavy barrel end adjuster clamp is free to flap around with engine vibration it can eventually start fatigue breaking strands of that unobtanium cable.

I know you have already spent your 80 quid and that must have hurt for that little part. However, on the early VW Golf's and Jetta's, they had a push pull cable that operated the advance lever on a VE pump where the mechanism is basically the same as the 6. It does not however have a big strong spring on it. It simply operates by push pull and its up to you to push it back in, just like an old fashioned choke.
Fortunately, I have 2 working wax stats, one I replaced myself (what a fun job that is!) but if ever one fails, I will just remove the big spring from the lever and use it like the old Golf/Jetta, with a push pull cable.

Steve

Steve

Steve,

My understanding of the difference between the VE pumps on the D24T vs the 1.6 is a little different. You're right that the D24T setup is under tension where the 1.6 setup is not. However, if I've got it right, that difference is not the result of a big spring applying return force, but rather a function of the location and action of the cold start advance lever.

To my recollection from the last time I had one apart: in the Volvo pump, the lever moves a ball stud on the inside of the pump housing. The ball stud directly contacts one of the "rungs" of the roller cage, moving the cage and rollers however many degrees to effect a timing advance. The Volvo has the CS advance lever mounted on the side of the pump body, and it has minimal mechanical advantage on the roller cage -- that is, for timing advance to take effect the lever moves only a short distance (maybe 15-30 degrees at the most) and with considerable force required. Probably the reason for that short travel range is due to the coinstraints imposed by the limited distance that the wax thermostat is able to move. I believe the high force required to move the Volvo pump's CS lever is a result of the force necessary to move the roller cage w/o much leverage. The external spring is fairly lightweight. (You can remove this spring and you will see that it is still not much easier to actuate the lever.) I think the spring is there mostly for the health and longevity of the CS cable and rest of the mechanism, so that there would be something to pull the lever all the way back against its external sheetmetal stop tab after the lever's internal ball stud backs off from contacting the roller cage.

The VW 1.6 pumps, if my assessment is correct, use quite a different system. The cold start lever is located lower in the body on a Rabbit pump, down in the area of the dynamic advance piston. (In the same location where, on a D24T pump through 1984, there is just a diamond-shaped cover plate, and on 1985+ cars the high altitude compensation advance solenoid is located.) The lever on those pumps moves a much greater distance with much less force -- the difference between advanced and normal positions on a Rabbit, for instance, is almost 90 degrees, and there is a detent at the end of the lever travel that the Volvo pumps don't have. My suspicion is that the advance mechanism in these Rabbit pumps works on a sort of screw principle where the lever's rotational movement horizontally displaces the advance piston in the bottom of the pump, and physically shifts the whole dynamic advance system (and roller cage) that way.

Basically to my understanding it's just two ways of skinning the cat, but with differences -- one which is tailored to operation by human fingers working through a plastic knob and skinny Bowden cable, and the other which is better suited to big mechanical forces applied by fair size springs and a much heftier cable. I believe it would be possible to convert a Volvo pump to use the 4cyl-style manual advance system, but probably the existing advance setup would need to be removed and covered with a side cover plate, and then a manual advance mechanism from a Rabbit or similar would have to be installed in the bottom of the Volvo pump. Or alternatively, a custom pump could simply be built using Volvo internals, aneroid, and head in a Rabbit pump case.

Hope my ramblings are making sense, as I write from Europe with jet lag... I will see if I can find some pictures to demonstrate.

George