61 ELN - THE ENGINE
Part Four: Ancillaries
61 ELN - THE ENGINE Part Four: Ancillaries |
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As mentioned above, the oil pump clearances were just about within specification on examination. However, both 'halves' of the pump were stripped and the mating faces lapped to just take up a little of the wear.
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The pump was then reassembled using a very thin film of French polish on the mating faces. I was unable to do a comparative test before/after stripping, but in a tub of old oil, turning the pump whilst holding the pressure against my finger seemed to show no serious flaws. Let's keep our fingers crossed on this one.
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Testing the oil pump - the unscientific way! |
The oil pump plus strainer were then reassembled to the engine, mating nicely with the distributor drive coming off one idler wheel on the timing chain, all of which had also been stripped, examined and overhauled where necessary. The cleaned sump cover was then reassembled (after what seemed like weeks of cleaning). The engine was then raised into the vertical position on dropped onto a four-wheeled trolley that I'd cadged off the scrap heap at a local garage - ideal for the purpose. Now we were really looking like progress had been made!
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The original Bosch distributor looked in a pretty poor condition: externally very corroded and it could not be turned by hand. Once again, the familiar sequence of strip, clean, examine, repair and re-assemble was followed. Disassembly had to be complete in this case as the seizure was traced to rusting between a washer and the drive 'dog' at the base of the unit. Wear to the advance - retard mechanism was evident but with a bit of restrained filing this was overcome. Fortunately, the vacuum diaphragm remains sealed OK.
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The octane compensation mechanism (cable operated from the dashboard to adjust timing to the variety of fuel grades available post-war) was also stripped and found to be generally OK. After much brushing, the body of the distributor was repainted matt black and then re-assembled.
The W186 has a single piece inlet manifold coupled directly to a two-piece exhaust manifold. The purpose of this is to improve the cold running performance by heating the inlet manifold with the exhaust gases. The degree of heating is controlled automatically (in theory) by deflector plates on axles which direct exhaust gasses to the underside of the inlet manifold when cold. 'Thermo-springs' on each axle then rotate the deflectors to direct most gas directly down the exhaust manifold on heating. Needless to say, the whole thing had seized-up years ago, and the Thermo-springs had corroded to virtually nothing.
After the manifolds were parted, the axle shafts were eventually freed after much heating with a blow torch. The balance weights were removed and the whole thing well lubricated with copper grease. I then cleaned the exhaust manifolds with a rotary wire brush (another Al Jolson job!).
The throttle linkage was removed from the inlet manifold, and another intensive cleaning task begun - a real tricky one this: just hours with a toothbrush and degreasing solvent.
Both carbs were disassembled completely and inspected. In both cases, unsurprisingly, the throttle pump diaphragms were completely rigid, any trace of flexibility having been long lost. One throttle pump presented a conundrum: it looked to have been assembed in the correct manner, but in a different way to the other! Detailed study of the exploded diagram in the workshop manual eventually revealed that it had indeed been assembled incorrectly whenever it was last serviced. No wonder the performance of this car was a bit 'iffy' in its latter years!
All components were shown to the rotary wheel to clean them up, but the fuel staining on the carb body remained stubbornly attached: nothing I tried would shift it from the nooks and crannies of its diecast body. On Ray's advice I resorted to dipping the body, briefly, into concentrated Sodium Hydroxide solution. This did the trick although it is rather disconcerting to see your valuable carb. body effervescing as it gives off bubbles of Hydrogen! Nevertheless, the end effect was what I wanted, and no serious damage to bores or threads was evident.
The carb. bodies and float chamber covers had both suffered 'die-cast distortion' with time. The appropriate mating faces were therefore either milled or lapped to enable improved sealing between parts. After further cleaning, both carbs were then reassembled using 'Royze' carburettor tune kit SO-5K: about £10 each from Star Classics and very good value in my view as virtually every gasket was included plus brand new needle valves!
The engine side covers had suffered internal corrosion from the residual dampness left within the water jacket. Both covers were cleaned as best I could then were taken to Redditch Shotblasting (01527 529659) for more aggressive treatment and zinc coating. Subsequently, they called me to say that pin-holes had become apparent after shot blasting, and that these should be closed-off before plating. My father dropped some weld into the worst holes and then, along with some other pipes and components, they were returned to Redditch Shotblasting for finishing off. The end result looks watertight (I hope it is!) and quite smart too - about as close as I could get to the original cadmium plated appearance. New gaskets were made from 0.75mm 'Klingerite' material; the covers were then reattached to the engine.
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As mentioned previously, the oil filter, a wire-wound type, was completely clogged with grime and took some cleaning-up. The same was true for the oil filter housing. The poppet in the filter by-pass valve, made from a thermosetting polymer of some description, appeared badly grooved perhaps as a result of prolonged operation due to general clogging-up of the oil filter. Ray turned-up a new one from PTFE and this was installed OK. The two oil pressure relief valves were also disassembled and cleaned-up. The spring forces were checked and found to be within specification.
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The installation of the water pump on the W186 is quite unlike any other car that I have ever seen. Specifically, the conventionally positioned dynamo has an output shaft on its rear which is fitted with an internally toothed drive. Using an intermediate nylon toothed drive, this then connects to the input shaft of the water pump. These two ancillaries are therefore in an extraordinary 'tandem' arrangement. It is assumed that this arrangement was selected to reduce the overall length of the engine from front to back, the usual position being on the end of the cylinder block.
Not surprisingly, the water pump was seized solid on removal. Stripping revealed the main housing of the centrifugal impeller to be clogged but in good condition. The four threaded holes for the mounting of the impeller assembly were not in too good a state so Dave at work re-tapped them and dropped in some 'Helicoil' thread inserts. However, the impeller assembly had definitely seen better days! Firstly, all the bearings and seals were in a pretty poor state, but of prime concern was the main shaft which had incurred severe pitting during its working life. I was obviously not the first person to realize this as someone (perhaps in deepest Kenya?) had previously attempted to fill the pitting with braze. I suppose this was potentially a successful means of recovering the part providing the shaft was turned or ground afterwards. Instead it was clear that excess braze material had been taken off with a file! The approximately round profile of the shaft had done no favours to the seals and, subsequently, further pitting had then taken place around the repair: overall, this shaft was definitely suffering from a 'lack of newness'!
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Water pump body |
Ray came to the rescue yet again on this one - the impeller and drive cog were removed and Ray then turned-up a replacement unit out of stainless steel. New seals and bearings were then fitted (all cheap and easy to find: all seals and bearings encountered so far have been standard metric ISO sizes) and the job was complete. In writing this, it all sounds so easy in retrospect, but this job was typical of many in that it took much graft and skill to disassemble such parts that had been bonded together in a wet environment for perhaps 43 years! No, this was a tricky task like so many others.
The Bosch dynamo appeared in a reasonable condition, although it would have been folly not to have taken it apart for a full examination. Again, with rotating electrical machines as another of his specialities, Ray jumped at the task. Within no time at all, I had a refurbished dynamo back in my hands with the commutator skimmed and a number of dodgy connections in the stator coil remade to ensure future reliability. I cleaned-up the drive pulley, painted the body with black engine lacquer and reassembled it to the engine using a new dynamo clamp, again crafted from sheet by Ray.
Dynamo with water pump to the rear.
