As you may see from this cooling system diagram the heater matrix is plumbed in parallel with the EGR (exhaust gas recirculation) valve and is fed with water into the lower part of the matrix. It would seem that as soon as even a tiny amount of air enters the system the flow through the matrix will be impaired, and at best the flow isn't great as the route down to the EGR is much easier - good old gravity ! I had a good check of the pipes during a couple of mornings runs to work, jumping out every five minutes and feeling the relevant hoses and it was obvious that the heater got very little flow compared to the rest of the circuits. I set about a plan to improve this.
Basically I have moved the pipes so that rather than the EGR and heater being in parallel they are now in series. The water flows into the EGR valve, out of that on a new hose I have installed and to the top pipe of the heater, then out of that and return via the normal pipe. I used a foot of 16mm heater hose, two jubilee clips and two 15mm copper pipes made into stoppers. Actual pipe-work should take you around 15 minutes ! My only concern was the flow out of the IRD cooler, but on looking at this the flow for that remains exactly the same relative to the other items in the system.
The results were amazing, total transformation of the heater system. I now get warm air within two minutes of driving off and full heat in around five minutes. For the first time I even have to turn the dial off full heat whilst driving !
Note : this seems to apply in part to the 1.8 petrol engined vehicles also, but the heater is bypassed by the IRD circuit which takes a little more re-plumbing to make it run in series correctly - I'm sure it could be done though.
The prop-shafts are on splines onto the VCU, with a single bolt into the end to hold it on. If you undo this bolt a little then you should be able to use a wedge between the UJ and the bolt in order to force the joint apart. One of mine came off with a good hit on the wedge, but the other I had to actually dismantle the UJ and get it in a hydraulic press.
When this is all apart you can press the bearing out of the race and read the part number off the side. I bought new ones from rswww.com for about nine pounds each. Fitting them was relatively easy, and putting it all back together and lifting back onto the car similarly so.
Once it was all removed (only about a 2 hour job, getting the cooler hoses off was the hard part as with it jacked that high I had to climb on top of the engine to reach them !!) I split the casing on the bench and had my first look inside. The results were pretty horrific, hard to believe it was able to drive at all - and I was definately lucky that the damage didn't extend a lot further than it did.
The damaged gear in the last picture is the pinion which drives the prop-shaft from the rear of the IRD. After stripping the box further I discovered that the main reason this was able to chip its teeth this badly was that the crown wheel that drives it off the shaft was able to move away from the pinion quite significantly due to a worn bearing on the shaft support. In this next picture you can see how this bearing has worn down so badly that the needles fall right out of the race even, it hardly looks like a bearing anymore !
In the upper-left of the picture you can see where some of the teeth on the crown wheel have broken off also, it was all pretty messy. After some frantic phoning around though, with almost everyone telling me that only a complete unit is available at huge cost (come on guys, someone must make the ones that you're selling right !) I found a local supplier who could source the two gears that I needed. He was really good, and in the end I let him replace all of the bearings as well since I was running out of time and wanted it back on the road. The result was excellent, a very tight box with all new shims and reset end-floats etc which I have far more confidence in than it seems the original units deserve.