ECR Posted October 23, 2016 Share Posted October 23, 2016 Prompted by a friends recent problems and my own experience …. A dry sump scavenge pump needs the ability to extract oil from the sump faster than the engines oil pressure pump can deliver it. This necessarily means that the scavenge pump will be running with little or no oil passing through it at times. The pump is no doubt designed to cope with this but shortage of oil lubricating its workings will inevitably lead to some degree of wear. Add to this, mechanical wear caused by any metallic particles not caught by the pre scavenge pump mesh filters and it is clear that eventually the performance of the pump will deteriorate. When that happens (over a period of time of course) the scavenge pump starts to struggle to overpower the delivery of oil from the pressure pump. At this stage, the oil in the system begins to collect in the sump rather than being returned to the dry sump oil tank. Depending on the capacity of the tank and the engine speed, that might not be an immediate problem (other than perhaps oil in the sump becoming aerated by the thrashing from the crank), but drive a long straight at high revs and the dry sump tank can empty starving the pressure pump with inevitable consequences ….. Dry sump scavenge pumps are not a fit and forget item. They should be stripped and inspected for wear (the regularity of this depends on use of course). An extra hole in the block is the penalty of ignoring this ……. What initially puzzled me was that before I started out on my fateful run, I had checked the oil level and found it fine. Why then did my engine seize through lack of oil? The above points explain it Link to comment Share on other sites More sharing options...
Paul Deslandes Posted October 23, 2016 Share Posted October 23, 2016 Ouch Roger , that had never occurred to me as a potential problem although, having said that, I remember helping a fellow sevener some years ago add a second hand Caterham dry sump system to a C20XE Vx. In the process we dismantled the scavenge pump and the scouring of the pump body internal bores were so bad that he either junked it or had it refurbished, I forget which. On reflection I dare say that that pump could well have caused a similar issue.Paul Link to comment Share on other sites More sharing options...
ECR Posted October 23, 2016 Author Share Posted October 23, 2016 The VX scavenge pumps are no longer available new so rebuilding (by Titan) is the only solution now Link to comment Share on other sites More sharing options...
OliverSedlacek Posted October 23, 2016 Share Posted October 23, 2016 I would have thought that the pressure pump and the scavenge pump get more or less similar abuse and should wear at similar rates. Failure of the scavenge pump drive will be seriously bad news of course. I'm reminded of the woes Gordon Murray had with the "Low line" Brabham BMW because they hadn't twigged that in a sustained high G corner the oil in the cylinder head wasn't draining back to the scavenge pump inlet due to the cant on the engine. Link to comment Share on other sites More sharing options...
Ian R Posted October 23, 2016 Share Posted October 23, 2016 Pretty sure the scavange pump causes my engine to let go at Brands earlier this year causing a holed block and sump. Titan did rebuild my pump as part of a full engine engine rebuild. Titan did Link to comment Share on other sites More sharing options...
ECR Posted October 23, 2016 Author Share Posted October 23, 2016 "I would have thought that the pressure pump and the scavenge pump get more or less similar abuse and should wear at similar rates." Not in my experience unfortunately Link to comment Share on other sites More sharing options...
garybee Posted October 23, 2016 Share Posted October 23, 2016 "I would have thought that the pressure pump and the scavenge pump get more or less similar abuse and should wear at similar rates." The pressure pump should always have a supply of oil as it is fed from the oil tank. The scavenge pump should run on an interrupted supply of oil as it would ideally have a flow rate in the region of 20% greater than the pressure pump. I would expect this to give them very different wear rates, as experienced by the OP. Link to comment Share on other sites More sharing options...
Paul McKenzie Posted October 23, 2016 Share Posted October 23, 2016 " The VX scavenge pumps are no longer available new so rebuilding (by Titan) is the only solution now".............and my rebuild cost at Titan was more than the original cost of the pump Link to comment Share on other sites More sharing options...
ECR Posted October 23, 2016 Author Share Posted October 23, 2016 There's a surprise ......... Link to comment Share on other sites More sharing options...
F355GTS Posted October 24, 2016 Share Posted October 24, 2016 I successfully bought parts from Titan to refurbish mine on 2 or 3 occasions are they not supplying anymore? Link to comment Share on other sites More sharing options...
ECR Posted October 24, 2016 Author Share Posted October 24, 2016 My (third hand) information is that they no longer supply parts. It would be worth a phone call to check though Link to comment Share on other sites More sharing options...
TomB Posted October 24, 2016 Share Posted October 24, 2016 Titan refurbished my purple K series pump for £80-90 5 years ago when I rebuilt the engine. Link to comment Share on other sites More sharing options...
Superwhite R283 Posted October 24, 2016 Share Posted October 24, 2016 Titan refurbished my gold pump last year, a £100 ish from memory. Link to comment Share on other sites More sharing options...
Paul Deslandes Posted October 24, 2016 Share Posted October 24, 2016 As the Vx system supplied by CC used the original crank driven gear pressure pump, you could replace the scavenge pump with e.g. Pace which looks much the same. I have a full Pace system on mine and this replaces the in-built Vx pump with a third, pressure pump, 'module' added to the 2 stage scavenge assembly. The fitting arrangements will be different and require different brackets etc but functionally it would be the same.Paul Link to comment Share on other sites More sharing options...
ECR Posted October 24, 2016 Author Share Posted October 24, 2016 To be clear, my blow up was a few years ago and I now have a spare scavenge pump on the shelf ... Link to comment Share on other sites More sharing options...
Paul McKenzie Posted October 24, 2016 Share Posted October 24, 2016 " There's a surprise ......... [Weeping] " ....the fact that Alex had driven through the Moroccan (?) desert might have had something to do with the cost Link to comment Share on other sites More sharing options...
Slipper man Posted October 25, 2016 Share Posted October 25, 2016 Thanks Roger for tactfully not mentioning my name. For 'twere me! I now realise that my scavenge pump used to make a "clucking" noise, which later on it didn't. Like Roger, I had only just checked the oil level.I don't have the car back from East Europe, but it does look like Roger's analysis is the problem. I am also discovering that K-series parts are starting to get more difficult to obtain. The only new pump I could find was at Caterham, and I took their last one. I will also see if the old one can be rebuilt at an economis cost. The new one was a rather frightening £600! Link to comment Share on other sites More sharing options...
ECR Posted October 25, 2016 Author Share Posted October 25, 2016 There's apparently a very good R500 rebuild article in a back copy of Low Flying. By K Jecks I think. You might find it helpful...... Link to comment Share on other sites More sharing options...
A10ROX Posted October 25, 2016 Share Posted October 25, 2016 Should I be worried? How do you check for wear? Link to comment Share on other sites More sharing options...
Wrightpayne Posted October 26, 2016 Share Posted October 26, 2016 I recall Stu Forshaw saying scavenge pump refurbs should be a regular service schedule item, every few years (cannot recall interval tho').Out of interest would an oil pressure warning light, the type which illuminate at higher trigger pressure have prevented catastrophe? Ian Link to comment Share on other sites More sharing options...
ECR Posted October 26, 2016 Author Share Posted October 26, 2016 Good question David to which I confess I don't know the answer. A call to Titan may be informative. In the absence of that, speak with Keith, find out his mileage/type of use (circuit use will shorten the life of all components) reduce that by 30% (?). If you are in doubt, my advice would be to send it to Titan for a rebuild. I have a large low pressure warning light fitted and to the best of my rememberance, I didn't see it light. Perhaps it all happened too fast, or perhaps I just didn't see the light. Link to comment Share on other sites More sharing options...
TomB Posted October 26, 2016 Share Posted October 26, 2016 A chat to Titan might be useful to ascertain their recommendations. All we know they might have a refresh interval of X miles or hours that we as owners/users are not aware of. Link to comment Share on other sites More sharing options...
ECR Posted October 26, 2016 Author Share Posted October 26, 2016 I've mailed Titan asking the question ..... Link to comment Share on other sites More sharing options...
A10ROX Posted October 26, 2016 Share Posted October 26, 2016 As A10ROX is in service with Stuart at BookaTrack I've asked him ... Link to comment Share on other sites More sharing options...
ECR Posted October 26, 2016 Author Share Posted October 26, 2016 Probably get a more helpful answer than I've received so far ....... Link to comment Share on other sites More sharing options...
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