Low oil pressure

[chuck1006]

When 1st starting my 100-6 my oil pressure is about 40 at idle (600 rpm) and 52 at 3000 rpm. After a 15-20 minute drive in Phoenix (105 degrees), the oil pressure is down to 5 at idle and about 25-30 at 3000 rpm. I am working on getting the engine to run cooler but what else could be causing the low pressure? The rocker arm was rebuilt but the oil pump was not. Could be be the pump? Anything else to check? The gauge seems to work OK but is not correct for my 100-6 so I am having a correct one rebuilt for it now.
Thanks,
Chuck

 

[AndrewMawson]

My otherwise OK BJ8 was showing similar figures to that when I got it. Especially bad when oil good and hot after a fastish run but no signs of excessive oil pouring out of rocker shaft etc.

Having replaced the oil pressure relief valve & spring to no effect I changed the oil pump and totally cured the problem - now run at 30 psi at 500 rpm tickover hot and 50 on the fly.

Old pump measured 'OK' against the book with feeler guages but had very slight scoring on the body.

Original pump was the gear variety, new one is the (older style) vane pump. /ubbthreads/images/graemlins/england.gif

 

[chuck1006]

Thanks for the input Andrew. Where did you get your new pump from? Did you select the vane type or is that all they had? Do you know of pros and cons of the vane vs gear type?

 

[AndrewMawson]

Chuck,

As per my message offline it was a vane type from SC Parts by Gatwick Airport https://www.scparts.co.uk/sc_homepage.asp they have a useless web site but a good catalogue !

I suspect that the vane type have a greater swept volume per rev than the gear type and probably the gear type took over on price grounds rather than technical superiority

 

[WALTER]

I have the same problem on my BJ8. How difficult is the oil pump to replace? Does the engine need to be pulled?

Thanks
Walter

 

[AndrewMawson]

[ QUOTE ]
I have the same problem on my BJ8. How difficult is the oil pump to replace? Does the engine need to be pulled?

Thanks
Walter

[/ QUOTE ]

Walter,

I used my pit: Drop the sump, unbolt the old pump, clean all the gasket surfaces, bolt on new pump with new gaskets, likewise the sump. End to end was perhaps 2 hours (plus shower time !) The only complication I had was when I came to drop the sump it wouldn't come off at the front despite all bolts being out. Turned out someone had put a bolt in the front engine cover plate that was slightly too long and it fouled the sump - just a matter of backing it out and remembering to tighten it ! /ubbthreads/images/graemlins/england.gif

 

[WALTER]

Thanks Andrew,
Now, if I go to Moss for a pump I have the choice Of standard ($240) or upgraded ($480). Any thoughts? Better sources?

Walter

 

[AndrewMawson]

[ QUOTE ]
Thanks Andrew,
Now, if I go to Moss for a pump I have the choice Of standard ($240) or upgraded ($480). Any thoughts? Better sources?

Walter

[/ QUOTE ]

Walter,

No experience of the Moss pumps or what they call standard or upgraded. I bought a "rotor" type as fitted to the earlier cars as this is all that SC Parts local to me carry. They charged me £99 plus VAT. The original in the BJ8 is a gear pump which I suspect has lower output per rev than the rotor type. /ubbthreads/images/graemlins/england.gif

 

[Healey 100]

Wait on that pump! I think your oil pressure sounds fine to me, it's about what my 100 has had for the last 25 years of driving it.

You don't say what kind of oil you are using. Suggest you go to 20-50, that might give it a bit of a lift.

Since you have repaired the rocker shaft, the oil pressure is probably low because of wear in the main bearings. I seriously doubt if the oil pump is warn, there is really not
much that can wear in those gear pumps. But I suggest you relax, I think 25 to 30 psi is plenty of oil pressure for these cars. Mine actually runs lower than that, and I would not consider replacing the bearings or the pump unless it were much worse or I had the engine apart for other reasons. That replacement of the oil pump is not a small job. I would not do it unless I was rebuilding the whole engine -- then you can get the oil pump, main and rod bearings, pistons, rings, etc.

That's my two cents....

ps, I would not make a big decision like you are about to without confirming that the oil pressure guage is reading accurately.

Bill S
Albuquerque, NM

 

[AndrewMawson]

Healey 100, I must take issue with you on that one '..replacement of the oil pump is not a small job.' It is IF (and its a big IF) you can get good access under the sump. Over a pit or on a ramp it's relatively trivial to change the oil pump - certainly that's my experience on a 29K engine in my BJ8.

Also the old gear pump, although slightly scored round the periphery, measured 'good' with feeler guages, but putting the replacement 'vane' pump in restored pressure from under 5psi at tickover / 25ish at speed to 25ish at tickover and 50 psi at speed with not much variation between oil VERY hot and just warmed up, whereas before when oil very hot it hardly registered at tickover. Now at least it's more in the comfort zone.

 

[Stretch]

I had a similar problem with low oil pressure once the car warmed up. I rebuilt the rocker assembly and it really needed it, but oil pressure stayed low. I pulled the oil pump and took it apart. Saw wear and scoring. So, I replaced it, and oil pressure is now normal. Looking inside the pump was a relatively easy check before going after the major engine bearings. I just raised the car onto blocks so I could get under it, and the job was relatively easy.

 

[WALTER]

You guys are killin me!!

Anyone else .........has anyone lost an engine due to low oil preasure?

so confused,
Walter

 

[Dave Russell]

[ QUOTE ]

Anyone else .........has anyone lost an engine due to low oil pressure?
Walter

[/ QUOTE ]
On low pressure no. On zero pressure yes. What you may not understand is that what the needle position should be, according to subjective feelings about such things, is not usually what is actually required.

People are just more comfortable with an oil pressure needle that runs at the higher end of the scale or at least doesn't go below half. If half scale on a gage is 50 people get uncomfortable when it isn't there. No matter that it is widely agreed that 10 psi/1000 rpm is adequate. Just human nature. If full scale on a Healey gage were at 50 instead of 100, few people would ever worry.

There is a reason that most new cars don't have any calibration markings on them & are set to run at middle of scale or higher, no matter what the actual pressure is. Some "pressure" gages are actually a switch that comes on at low pressure & puts the needle somewhere near mid scale.
D

 

[chuck1006]

Thanks for all the info. I purchased an vane type oil pump from Moss and installed it before my rebuilt gauge was ready. The oil pressure improved to 20 at idle and 42-50 at approx 3000 rpm when hot. My correct style ebay bought oil/water gauge was rebuilt at Mo Ma Manufacturing - instrument repair 1321 Second Street NW Albuquerque, NM 87102 and I was totally satisfied with the results. I will be sending my speedo gauge there soon since it is reading very high. After the rebuilt correct type gauge was installed, it read the same as the old so, my old wrong type Jaeger gauge was OK in calibration. The process to change the oil pump is easy enough if you don't mind spending a couple of hours on your back to get all the bolts off and back on the oil pan. Get a soft pad to lay on and it is easy enough even at my age. I agree with Andrew that the oil pump is best to replace if the oil flow thru the rocker looks OK. If you don't agree, I have an used oil pump to sell cheap.

 

[chuck1006]

PS. I forgot to say I was running 20W-50 oil with the old pump and when the engine was very hot my oil pressure would go to zero at idle if I didn't rev the engine.

 

[EV2239]

I never got to drive my BJ7 very far before I sent it to the body shop for restoration, the engine sounded very sweet and didn't use much oil, but oil pressure was low. Now it's back I find that after thirty miles it is below 30 psi, so having read this thread I dropped the sump and took the pump off. It is a gear type and completely worn out, so I have a vane one to go in.

Interestingly the big ends have obviously been in there for a very long time and there are score marks, but the crank is in spec, so I'm fitting new shells while the sump is off.

I'm interested to see what it runs at when the work is done.

 

[bob hughes]

Just finished my engine rebuild and changed my pump to a DW high output job at the same time. I have excellent pressure on tick over and running at 50mph on a hot engine but of course everything is new.



Bob

 

[BOBBYR]

Hi Bob, Hope you are doing well. I was wondering what type of pump you have and what vender you used to purchase it.
Regards, Bobby R

 

[EV2239]

I blagged a second hand 100/6 vane type or high output pump for my BJ7, it was in spec and it gave a huge increase in oil pressure, which is now as the book says. I'm very pleased because this engine runs beautifully and pulls from 600rpm in top gear. No need for a rebuild now.

 

[Bob_Spidell]

Denis Welch sells a vane-type pump for use in non-racing applications.