7HP oil feed

[DougGillanders]

I am a recent convert to Jowetts, in particular the 7hp in what I think is a long 2. On starting to fix things which didn't work when this car was bought, I turned to the oil pressure gauge as it didn't register any pressure. I temporarily switched it for another one - which also didn't register any pressure. Attention then moved to the pressure relief valve. which on removal didn't appear to have worked for while as the spring was way too short amongst other faults. A replacement was obtained through the good auspices of Paul Beaumont and Michael Kavanagh. This was duly tailored to fit and piped in. Still no pressure registering! The 5th edition owners manual suggests priming the feed side of the oil pump when the oil does not exit from the pump - duly done. Still no pressure. Removal of the pipe at the sump end led to a small trickle exiting from the fitment in the sump. Removal of the fitment led to a gush of oil out of the sump. It appears that the (very clean) fine wire mesh filter on the fitment is too fine for the oil to flow through in suitable volume. The afore mentioned manual mentions filling the sump with (3 pints of) Castrol XL. The oil in the sump is of unknown type but appears to be of 20W50 consistency which when put of the mesh filter has great difficulty in running through it. Only a trickle exits from the other side.
Can anyone please confirm that 3 pints is the correct amount of oil to be in the sump and am I missing something obvious

[Chris Spencer]

Doug - Welcome to the forum and Jowetts, I don't know the answer but a couple of very wise, very knowledgeable fellow members shall be along very shortly with the answers for you

[Forumadmin]

The fine mesh will not let oil with long polymers (i.e. 20/50) go through. The single SAE 30 (or even 20) in the winter oil has none of that stuff which clings to metal surfaces and hence will flow freely. I do not know the quantity required. The Pitman book 1953 (2nd) edition pg 64 has a good explanation of the lubrication system. The 1959 (3rd) edition in the Gallerydoes not have the pre-war explanation.

[george garside]

I presume Doug is talking about a vintage engine with the external oil pump on the timing case as this is the one that needs priming. The pitman book only covers the Steve Pool engine from 1930. I am a bit puzzled by the reference to oil pressure guage as the vintage cars only had a 'button'' on the dashboard although a pressure guage could have replaced it at some time.

george

[DougGillanders]

Yes, the engine is the vintage type (1927) with external oil pump on the timing case, requiring the oil to be "sucked" from the sump to the timing case top and hence needing to be primed if there is no oil in the pipe. The pump works as when oil is fed on the input side, it is pumped to the output side when turning the engine over.
I suspect the gauge has been added at some later stage as it is not a Jowett original and only reads up to 25psi.

[Tony Fearn]

Hello Doug, and another welcome from me to the forum.
My experience is only with the early pre-war 7hp Jowett, so I can't help with the oil problem in your 1927 long 2 as the PRV is so much different to the vintage type.

Pre-war pressure relief valve.jpg

You mention help from two of our Spares people, and if you give Mike a ring, (telephone number in the Membership List), perhaps the problem could be solved.
Regards,
Tony.
P.S. I was very interested in Keith's 'long polymer' theory.

[Keith Clements]

Scott and I had a long running saga with the PRV from California to Carolina on the cross USA trip .

Also PTFE based additives like Slick 50 can also have the clogging effect.

You can notice the clogging effect on a petrol filter which is a very fine mesh. This can block your petrol feed if some oil has been introduced into the petrol tank.

Have a read of this.

[ian Howell]

Doug: -

A little late perhaps, but welcome to the club website and I assume/expect a new member?

I have a 1930 7hp Long Four with the oil pump in the sump, so not the same problems, however: -

I was interested to read Keith's comments about oil filters (well, 'strainers' really) and I must say that I have never noticed a shortage of oil pressure when starting up (with oil cold) and I am using 20/50 with a 'storage' additive which was like syrup when I added it, so the oil must be getting through the strainer mesh - at least on mine.

I did rebuild my relief valve a while back (well not mine - the car's) but it did not solve my problem of low oil pressure when warm. That is almost certainly due to slack in just about everything that moves in the engine!

[Keith Clements]

If it is the standard mesh then you should have no problem as it is open weave. But I know some people who have put finer mesh on the pick up hoping to keep the bearing shavings out of the pump. All it does is increase the likelihood of such shavings.

The 20/50 goes through low micron filters OK because it is under positive pressure. The sucking action required to prime the pump when there is a fine mesh, cold oil and long polymer stiction may be what causes lack of initial oil pressure. The pump probably finds it easier to suck air past itself than create a negative pressure to suck the oil up. There is however lack of quantitative experimental evidence for this but I do have some pick ups with fine mesh and some with coarse mesh so next time I have my pump tester operational!....

You probably have seen evidence of this stiction by the high oil pressure on cold start. The viscosity reduces rapidly as can be seen by the drop from over 100 psi to 50psi in a few minutes.

[ian Howell]

50psi?!!

I'm lucky to get 15 oz/sq ft! Still. as Keith said previously 'it's flow, not pressure that really matters'.

Phew!

[Keith Clements]

It is also important that the flow is getting to the right places. Without pressure, oil might not be delivered to some of the outlying bearing surfaces which are starved by the flow from just one oriface. Pressure also helps distribute the oil across the whole bearing surface, rather than hold it in the groove delivering the oil. I have a similar problem when setting up the irrigation system for my garden!
Some people have added extra oil delivery pipes to the rear bearings on Jav/ Jup or to the rocker shaft to overcome this starvation. How this might apply to the 7HP and to the sedate way such cars are used may not be relevant.

[DougGillanders]

I have at last managed to get an oil flow through the oil pump by priming the pump with a head of oil fed into the inlet side of the pump and using a suction pump to draw the oil from the sump. The pump needed a good bit of oil through it before it would work properly. The oil I have used is Millerol SAE30 and I put 2.5 litres in, which, when I used a home made dipstick in through the oil filler tube, came well above the oil feed outlet to the oil pump. I cannot understand the dipstick system on the engine as it seems to stick in the last position it has been moved to! I thought I had set the PRV at around 25 psi using a compressor and pressure regulator but there must have been a large air leak because on start up the oil pressure rose to just short of 50 psi. It is now backed off to 25 psi (gauge only reads to 25psi) using the PRV but I have yet to check the value when the oil is hot - but I at least have an oil feed.

[ian Howell]

Doug: - Re: Sticky dipstick,

I had a similar problem on my 1930 Fabric Saloon, the dipstick appeared to be missing but in fact was only stuck in the 'down' position. This turned out to be due to a kink in the bit of wire that pops up with the float in the sump.

I cured the problem by soldering a bit of copper brake pipe about 3"" long to a bit of wire coat hanger (whatever would we do without them?) and then working the pipe bit down, and up, and down, and up - - - - (you get the idea) until the rod was straight enough to move freely in the tube.

Fiddly job, but very satisfying and worth a try.