Cold Start Waxstat

piper109 · #1 05-01-2012, 01:26 PM

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

v8volvo · #2 05-01-2012, 03:10 PM

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

FJ40Jim · #3 05-01-2012, 04:48 PM

I like the idea of using the manual timing advance vs. the thermo widget.

I have a rabbit pump on a shelf, and a complete D24T engine on a stand. If there is anything I can take a pic of or compare between the two, LMK.

piper109 · #4 05-02-2012, 04:47 AM

Hi George,

I had assumed that the Bosch engineers had chosen to keep things consistent from pump to pump.....silly me I should have known better!
Clearly your VE knowledge is way ahead of mine and thank you for applying the correction. Your explanation is very cohesive and easy to follow.

Are you in Europe for vacation reasons or VW reasons? Either way, enjoy the food and liquid refreshment. Just pretend that 1 Euro = 1 dollar, unless you are in UK of course. A well lubed pub lunch will dull the pain :-)

Cheers, Steve

Quote:

Originally Posted by v8volvo

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

ian2000t · #5 05-04-2012, 02:02 AM

Tried the new waxstat in a housing last night on the hob. Only took it to 70C so not to overheat it, and it extended about 20mm I think, then retracted when cool.

First time I have EVER seen one of these move lol!!! Now the fun part of putting it back on the car, and bleeding the air out of the top hose.

piper109 · #6 05-04-2012, 03:38 AM

Its not fun putting that thing together with the big spring. I have found it to be much easier with two long bolts that you take back out and replace with the correct ones 1 at a time. Mind those knuckles !

Steve

ian2000t · #7 05-04-2012, 04:42 AM

Yep, will try that method if I have some bolts with the right thread (most of mine are UNF though).

Failing that, I'll empty the swear jar ready!!

v8volvo · #8 05-04-2012, 11:00 PM

If you have access to a spare injection pump (even one off a different engine, i.e. 1.6L VW diesel, older TDI, etc), the pump head screws (the ones that hold the iron pump head onto the aluminum body) are the same thread as the cold start thermostat housing screws, but longer. They can help to get the process started of putting it back together.

Or better yet, if you haven't taken your existing CS housing apart yet already, there is a method that member ngoma devised and showed me that is the easiest of all. Before starting to loosen any screws, can pick up a set of small needle-nose vise grips (locking pliers), pull the rubber accordion boot forward off of its position at the point where the cable exits the housing, and clamp your vise grips onto the cable there to prevent it from receding back into the housing as you take the screws out. This way the springs stay compressed even while you have the rear part of the housing removed, so that you can put it back together with ease. The only tricky part with this method is working around the pair of pliers that are sticking out and running into your wrench.... but that is still easier than fighting those springs on reassembly.

Getting the threaded gland nut thing that holds the thermostat unit inside its case is also a little tricky esp if it is stuck.... hammer and screwdriver with the housing in a vise is one method though fairly brutal. I have been meaning to make a proper tool by modifying an old socket, which is probably the better method... could grind away the sides of the socket until it is just a cylinder with two fat tabs sticking out to engage the slots in the CS t-stat gland nut, and then wind it right out.

MoeTell · #9 11-30-2012, 08:31 PM

Where did you try attaching the guide wire and what kind of wire did you use? I have one from a lawn mower that I have set aside to use when the actuator on my own isn't able.
cars rent surfers paradise

Boots · #10 12-23-2012, 10:16 AM

My waxy wotnot is also on its way out. Up until the last few weeks it was working pretty well but now doesn't want to go all the way to the hot-running position.

(It has always drifted back to a little bit of advance/fast idle in really cold weather (0 deg C and below) when the engine is not working hard - don't think there was enough coolant flow to keep it fully actuated in these conditions...)

I'll be taking the advice re keeping the spring compressed and making a tool to remove the locking ring.

I'll try to get some decent piccies as I do it and post them up. Likely to be late in Jan when I get round to it though as I have the IP and rear brake pads to tackle first!