Oil leak at fuel pump

[horsa]

Thanks Lynn, something new for me to research as I have a hex bolt there for some reason. I probably filled the hole during restoration and promptly forgot about it....


Per Lynn's post below....I do remember fitting a sealed bearing so might have eliminated the grease fitting at that time. Thanks

[Lynn Eades]

There were two types of thrust bearings used, but a modern sealed bearing is probably the best. Then we are not inclined to over grease it, and end up with a stuffed clutch because it has grease in it.

[ajmac]

Great info there chaps, so if Andrews PRV is set at 10psi like the manual suggests, but isn't being used to regulate hot and cooled oil mixing as the original design intended, rather just dumping oil over 10psi back to the sump via the filler then there is a problem.

[andrew honychurch]

Fantastic, what a great wealth of knowledge there is out there. Its as good as having you all here inthe workshop with me, but without out me having to crack the tinnies!

No seriously , thanks a lot all of you, there are some really interesting points here.

I have to assume, maybe wrongly, that what I have is how it is meant to be on my vehicle. I cannot id the oil pump fitted to mine, as I have not an indpeth knowledge of what the other types look like, but as my vehicle is June 1944 and has the thermostatically controlled valves in the oil coolers , it seems that there may have been a change to the way the system is plumbed.

At present , my best guess is that I have the correct set up but a blocked or restricted cooler. Remember, that during my first tests and run to War and Peace the cooler was getting hot, i.e working. Now it is not. I reckon therefore that the restricition is opening the relief valve and that is whay we are seeing too much oil being fed back through the filler neck.

Much as I didnt want to do it, as its a pain in the arse job, it seems I will need to pull the cooler off and clean it once more with solvent to try to get it flowing ..

Given the low pressures on these engines, its seems logical that it would not need much of a restriction in the cooler or lines to cause the PCV to operate?

David, on the oil greaser, did you have a flexible pipe inside leading from this to the thrust bearing? If not, dont fit the greaser or it will dump into the bellhousing!!

I hope to report back later chaps, many thanks Andrew

[ajmac]

Good luck investigating.
Attached is a little single line sketch of the various Flathead V8 oil system layouts. Yours is the third one down, at least on the face of it!

On a well designed modern oil sytem you would have a PSV (Pressure Safety Valve) around the pump to protect from dead heading, this would be the highest pressure setting in the system and shouldn't lift in normal operations. After the pump you would have the main PCV (Pressure Control Valve) for the system and after that the TCV (Temperature Control Valve) directing some oil to the cooler and mixing it with hot oil to maintain a set temperature before sending it on to the oil filter and the things you want to lubricate! You would monitor the line pressure after the filter just before the things you want to lubricate.
In an automotive application it would be quite acceptable to combine the PSV and PCV into one PCV as part of the pump.

PS. The rear main is fed directly from the pump discharge before it ever gets to the top of the bell housing, thats what makes fitting a full flow oil filter almost impossible.

[andrew honychurch]

ok, so I have had time to investigate and this is what I have discovered.

1. The outlet pressure from the cracnkase/bellhousing is the nearest the left hand side of the engine, and feeds directly into my PRV.

2. I have established that I am getting flow back to the other elbow.

3. As the engine heats up, which takes a long while as I dont have thermostats in the cylinder heads, the oil cooler takes more of the flow and the relief flow to the filler tube slightly reduces. I hope and suspect that as the engine gets really hot there is less flow to this tube and more to the cooler.

4. I dont know quite why my system has been created, as its not in the TM but I think it probably works. MY suspicion is there is a design fault that means that the fuel pump fills up and if you operate on rough ground at speed as I was doing, it will spill out some of this oil

5. I can try to make a gasket for the fuel pump aperture which is better at resisting this oil flow.

6.I have oil pressure, I have oil cooling, and I have an engine that works, so until I can find a Chilwell ( or FORD USA ) mod sheet I think I am going to leave well along and try to avoid oil spillage by physical means.

Thank you all for the help on this, and if the problem continues I will post again, but until I have got the engine really up to temperature I cannot say for sure whether this relief valve flow will cease.

thanks

[andrew honychurch]

I am still struggling to work out why the British army modified the PRV set up as per mine on the above photograph. Of course I have no information on it as I have the original TM s . I have seen one other T16 with this set up, again ex British Army. I don't suppose anyone has any post war British manuals for T16's they could check in?

[Lynn Eades]

Andrew just something to consider. there is a rudimentary seal under the pump diaphragm. Can I assume you have not checked it. The seal supposedly stops oil getting through to the under side of the diaphragm from where it exits at the breather hole (in the bottomside of the pump casting. It has to have the hole. I do think your main problem is not here though.

[Tony Wheeler]

Originally Posted by andrew honychurch

I am still struggling to work out why the British army modified the PRV set up as per mine on the above photograph. I have seen one other T16 with this set up, again ex British Army.

It's certainly a brain teaser Andrew. I'm not familiar with carriers but here's my conclusion based on Ford CMP background. The PRV installed on your T16 is set up to reduce to engine oil pressure, which can serve only one possible purpose, namely oil cooler protection. Presumably they were prone to fracture, which is certainly to expected in copper pipe subject to flexing and vibration, which leads rapidly to hardening and fatigue crack formation. Copper pipe has long since been abandoned in vehicle applications for that reason. Flexing in oil cooler pipes would be induced by constant oil pressure variation, eg. start up and shut down as well as gear changes. Pipe bends are particularly subject to flexing, especially a 180 degree return bend if present, which I assume to be the case in carriers. Flexing force can only be reduced by pressure reduction, hence PRV installed by the British. Same principle applies in domestic plumbing to reduce "water hammer" by installing PLV (Pressure Limiting Valve).

Of course, we still have to explain why only the T16. Once again I'm not familiar with carrier production, but the possibility of such a mod only exists on the post '44 flathead, which ran 70 psi with the PRV in the oil pump itself, replacing the early type oil pump which ran 40 psi using the PRV in the front of the block. I should state here that I've never seen the 70 psi spec written anywhere except on the plate pictured below, which is occasionally found on Australian late production Ford CMP dashboards, ie. mid '44 onwards. However the early production dashboard, ie. commercial type, featured a 50 psi gauge, whereas the late production dashboard, ie. military round guage type, featured an 80 psi gauge. Hence while the plate itself is extremely rare, the gauges lead to me believe that all post '44 motors ran 70 psi. Certainly this particular T16 motor is post '44 high pressure, as evidenced by 80 psi reading. Once again, the very presence of an 80 psi gauge would indicate that.

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Presumably in carriers the British dropped these motors back to 40 psi or thereabouts, as on pre '44 engined carriers, using an external PRV rather than pull the motor down to perform the necessary internal mods. As such it's a relatively simple mod which would reduce maximum pressure considerably, and could also be expected to deliver more constant pressure, both of which would greatly reduce oil cooler flexing. Meanwhile it presents no problem for the motor, which simply reverts back to pre '44 oil pressure and flow rate, with the excess flow from the post '44 pump being dumped in the breather standpipe. The same location was used for oil return when fitting partial flow filters on early flatheads, except it was plumbed via the LH stud which was drilled for the purpose. Obviously the T16 overflow would be considerably greater, however we can assume it presented no drainage problem in British service.

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The other aspect of the British mod is removal of the 10 psi bypass valve, which acts to reduce cold oil flow to the cooler, by responding to abnormally high pressure due to viscosity. As such it's a rudimentary oil temp regulator, which if my reading of this thread is correct, was replaced by the British with a proper thermostat. At first glance it may be thought unwise to remove the 10 psi bypass valve, which in addition to it's intended function, would also protect the motor in the event of oil cooler blockage. However it can be seen from the carrier manual pages posted by Lynn that no such blockage is contemplated, presumably because no potential for blockage exists in service, owing to the cooler pipes being of far greater diameter than the engine oil passages. In other words, British removal of the 10 psi bypass valve is perfectly safe.

Given the adjustable PRV used by the British you're left with a choice Andrew. You can screw it down tight and let the flathead PRV take over, which will increase maximum oil pressure to 70 psi and eliminate all flow into the breather standpipe. However it may jeopardize the 70 year old oil cooler, which the British evidently believed even when it was brand new. Alternatively you can adjust the PRV to 40 psi to emulate the pre '44 motor, which will offer maximum protection for the oil cooler, but generate constant overflow into the breather standpipe, owing to 30 psi differential across the PRV. Remember you have 70 psi going into the PRV at anything above idle rpm, because it's coming direct from the 70 psi pump (minus a few psi to the rear main bearing only). Of course you can always choose somewhere between 40 and 70 if preferred, and if the original British setting can be retrieved it may provide some guidance.

As others have suggested the PRV needs to be set using a reliable oil pressure guage, meaning a capillary type rather than electric. This can be fitted temporarily in place of the existing sender unit, which despite its proximity to the OUTLET passage is actually connected internally to the RETURN passage, by means of a tapered bushing inserted at the passage intersection. This can be seen on the CMP diagram below, which I assume is identical on carrier motors. Obviously it's the RETURN pressure that matters, since that's what the motor receives. Note 10 psi bypass valve essential in this application, because filters are subject to clogging. Interestingly I've never seen this filter configuration implemented - to the best of my knowledge the early production CMP had no filter, and late production had a partial flow filter, with oil return direct to the sump via an external pipe.

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Another consideration is the oil temp thermostat, and there may be ways of checking its operation. Main thing of course is to confirm reasonable oil pressure through the full temperature range, allowing for the expected drop at full operating temp on worn motors.

Hopefully the above makes some sense of this puzzling British mod!