Oil Pressure

[David Edgar]

Twas about two weeks ago that I had the misfortune of having one of the
external oil lines break create a loss of oil pressure resulting in a
knock on my TC. My rescuer as able to bring my TC back to me on Thursday
and I proceded to determine what kind of damage I had. Taking a
compression test resulted showed 140/135/140/140 which looked good and
then tore down the bottom half of the engine to inspect. The number 4 rod
journal showed some scoring but all the other journals were quite fine.
Mains indicated .001 under standard (right where it was 15 years ago) and
three of the rod journals measured out at .011 under (again right where it
was 15 years ago). Took the crank in to have it manufluxed and if OK,
build up the #4 journal so as to have the rod journals ground to .020
under. Am having the Chevy rear seal conversion done also. Rest of the
engine looks fine visually.

Over the last 10 years I have been running about 40 pounds of oil pressure
when cruising and about 15 pounds at idle. Running at these pressures
resulted in no wear on the journals over the years. My theory is that
this seeming low pressure (everyone else I talk to reports 60 or more
pounds at cruising) was either acceptable or is a result of an
inaccurate gauge. I have been told that the insides of the guage can
become clogged and cause the gauge to read low and I should take a known
accurate gauge to test the working system. This is kind of hard to do
with the engine appart now.

My questions to everyone are:
How can I check the oil pump to see if it is pumping properly now?
What should I look for to determine if my pump is worn?
Should I just put the engine back together and then test and if necessary
then pull the pump off and repair?
What kind of oil pressure is adequate vs desirable?

Dave Edgar, TC 5108

[Skip Kelsey]

Dave:

The oil pumps used on all XPAG/XPEG engines is really over kill. They are a
solid gear type pump, and will pump more oil than you will ever need. About
the only thing that is usually necessary is to lap the end plate. ( the
part where the relief valve assembly is).Get rid of the wear swirls left by
the driven gear.
I would check the spring and ball for wear. If in doubt, replace these two
inexpensive parts. Other than that you should be just fine.

Cheers;



Skip Kelsey............................

At 01:09 AM 5/7/00 -0700, David Edgar wrote:

>Twas about two weeks ago that I had the misfortune of having one of the
>external oil lines break create a loss of oil pressure resulting in a
>knock on my TC. My rescuer as able to bring my TC back to me on Thursday
>and I proceded to determine what kind of damage I had. Taking a
>compression test resulted showed 140/135/140/140 which looked good and
>then tore down the bottom half of the engine to inspect. The number 4 rod
>journal showed some scoring but all the other journals were quite fine.
>Mains indicated .001 under standard (right where it was 15 years ago) and
>three of the rod journals measured out at .011 under (again right where it
>was 15 years ago). Took the crank in to have it manufluxed and if OK,
>build up the #4 journal so as to have the rod journals ground to .020
>under. Am having the Chevy rear seal conversion done also. Rest of the
>engine looks fine visually.
>
>Over the last 10 years I have been running about 40 pounds of oil pressure
>when cruising and about 15 pounds at idle. Running at these pressures
>resulted in no wear on the journals over the years. My theory is that
>this seeming low pressure (everyone else I talk to reports 60 or more
>pounds at cruising) was either acceptable or is a result of an
>inaccurate gauge. I have been told that the insides of the guage can
>become clogged and cause the gauge to read low and I should take a known
>accurate gauge to test the working system. This is kind of hard to do
>with the engine appart now.
>
>My questions to everyone are:
>How can I check the oil pump to see if it is pumping properly now?
>What should I look for to determine if my pump is worn?
>Should I just put the engine back together and then test and if necessary
>then pull the pump off and repair?
>What kind of oil pressure is adequate vs desirable?
>
>Dave Edgar, TC 5108
>
>
>
>
>
>

[Bob McKarney]

Dave - I can't answer any of your questions, but can observe that my TC
has been running 40 pounds oil pressure at speed and about 15 at idle
since 1975, even after major Mike Goodman engine rebuild in 1998.
Bob

[David Edgar]

Bruce -
That was an excellent article on oil pressure vs oil flow you attached to
the e-mail. Who wrote it? There were only initials at the end. Also,
thank for you comments as well. I should have all my pieces and parts in
a week and I can then put the engine back together.

Thanks everyone for the oil pressure and pump suggestions. I should be
back on the road soon. There was a thread several months ago and several
mentions recently on putting in a buzzer or other warning signal to warn
of no oil pressure. Mike Goodman showed me a little fitting that replaces
the fitting on the TC where the flex oil line joins the oil pressure
gauge line on the firewall. It comes from an MGB and looks similar to
the TC fitting but has a third threaded connection to fit an oil pressure
switch sending unit.

Dave Edgar, TC 5108

On Sun, 7 May 2000, Bruce J. Obbink wrote:

> David:
>
> I went through this oil pressure issue about a year ago and I will share my
> experience. Two of the more obvious "fix it" is put in a new ball and spring
> in the oil pump cap. This is what controls the pressure. Do not try and shim
> this set up. If everything else is working right you will get the right
> pressure. The oil gauge could also be a problem. After the car is
> re-assembled you can try an alternate gauge. You don't necessarily need a
> Jager gauge. Any pressure gauge will work. Oil pressure can bleed off the
> rocker bushings. Check these and if even slightly worn, replace them. Might
> as well do it now that you have the engine down. The cap of the oil pump
> needs to be smooth. Make certain that the gear in the pump hasn't worn down
> the cap so the clearance too great. You may have to put a belt sander in the
> vice, and very carefully smooth out the cap and then further smooth is on
> sand paper on a plate of glass. In my dilemma I could get to 35 pounds and
> no more. The end of the road was the wrong size bearings were in stalled. A
> .010 excess clearance will take the pressure down about 25 pounds. Once I
> re-ground the crank and installed the proper bearings, the pressure was
> perfect. So, you may find that your re-doing the crank and having it ground
> to the exact bearings, you may have solved the problem. You won't know until
> it is all back together. Trying to find a problem in the oil pump is not
> likely. Very little ever goes wrong with them. Good Luck Attached is a good
> discussion about oil pressure that was sent to me when I had my problem. I
> reproduced it in our club newsletter.
>
> Bruce Obbink
>
>
> Bruce J Obbink
>
> -----Original Message-----
> From: David Edgar [mailto:dedgar@pwa.acusd.edu]
> Sent: Sunday, May 07, 2000 1:10 AM
> To: T-ABC's Forever
> Subject: [mg-tabc] Oil pressure
>
> Twas about two weeks ago that I had the misfortune of having one of the
> external oil lines break create a loss of oil pressure resulting in a
> knock on my TC. My rescuer as able to bring my TC back to me on Thursday
> and I proceded to determine what kind of damage I had. Taking a
> compression test resulted showed 140/135/140/140 which looked good and
> then tore down the bottom half of the engine to inspect. The number 4 rod
> journal showed some scoring but all the other journals were quite fine.
> Mains indicated .001 under standard (right where it was 15 years ago) and
> three of the rod journals measured out at .011 under (again right where it
> was 15 years ago). Took the crank in to have it manufluxed and if OK,
> build up the #4 journal so as to have the rod journals ground to .020
> under. Am having the Chevy rear seal conversion done also. Rest of the
> engine looks fine visually.
>
> Over the last 10 years I have been running about 40 pounds of oil pressure
> when cruising and about 15 pounds at idle. Running at these pressures
> resulted in no wear on the journals over the years. My theory is that
> this seeming low pressure (everyone else I talk to reports 60 or more
> pounds at cruising) was either acceptable or is a result of an
> inaccurate gauge. I have been told that the insides of the guage can
> become clogged and cause the gauge to read low and I should take a known
> accurate gauge to test the working system. This is kind of hard to do
> with the engine appart now.
>
> My questions to everyone are:
> How can I check the oil pump to see if it is pumping properly now?
> What should I look for to determine if my pump is worn?
> Should I just put the engine back together and then test and if necessary
> then pull the pump off and repair?
> What kind of oil pressure is adequate vs desirable?
>
> Dave Edgar, TC 5108
>
>
>
>

[John T. Seim]

David Edgar wrote:

> My questions to everyone are:
> How can I check the oil pump to see if it is pumping properly now?

Should be no problem, as it was pumping before.

> What should I look for to determine if my pump is worn?

I just sent you am itemized "by the numbers" check of your oil pump.

> Should I just put the engine back together and then test and if necessary
> then pull the pump off and repair?

On a TC, you have to pull the engine, to remove the oil pump. On TD &
TF, you can extract the oil pump, by releasing engine from front motor
mount.

> What kind of oil pressure is adequate vs desirable?

It is the low idle pressure that you should worry about, not the running
pressure. When you rebuild the oil pump, replace the ball and spring.
Seat the ball to the ball seat. Surface the cover plate. Use plastigage
to determinbe the gear clearance to the cover plate. The housing might
have to be milled to obtain the correct clearance, as the gears also
wear into the housing. A rebuit pump will have 60-70 psi running and 40
psi at idle. A pump that drops to 10-15 psi at idle should be rebuilt.
You were wondering about your gauge accuracy. You can borrow another
gauge, and oil pipe (should you not want to change the connection at the
dash). Compare the readings between the the gauges.
John Seim, TC 6590

[PMS GB Ltd]

Message text written by "John T. Seim"

>> How can I check the oil pump to see if it is pumping properly now?

Should be no problem, as it was pumping before.<

Ah - It aint necessarily so! - not due to the pumps failure, but those who
have not done this before might not realise that they will need to prime
the pump with oil or a very light grease or all it will do is spin air
around without picking up any oil and just show no oil pressure - I have
had more than one engine, newly rebuilt, brought in with dry and ruined
bearings as the owner revved the engine trying to find some oil pressure on
first start up.

Regards

Clive

[CFritz7001@aol.com]

Clive,
Good point; priming the pump is the thing to do!
So is filling the filter with oil (if it's a vertically-mounted one)
before installing it. So is using a good quality assembly lubricant
liberally on all engine bearings and the camshaft lobes as the engine goes
back together. So is "spinning" the engine on the starter (with ignition
off) until one gets some oil pressure showing on the gauge, THEN actually
starting the engine.
Betcha dollars to doughnuts that one or more of these precautions were
not carried out on the fresh engine overhauls which resulted in ruined
bearings on first start-up.
Regards to all,
Carl Fritz

[PMS GB Ltd]

Message text written by INTERNET:CFritz7001@aol.com

> Betcha dollars to doughnuts that one or more of these precautions were

not carried out on the fresh engine overhauls which resulted in ruined
bearings on first start-up.<

Hi Carl - Yes in each case the guy said he had had no oil pressure - just
kept running the engine to find some and ended up scraping the dry bearings
to death. And as you point out, filling a vertical filter can certainly
save 10 seconds dry running time.

I always prefer to turn the engine over on the starter or by hand - without
the plugs in - to ensure I've got oil up to the rockers before firing up
and giving it 5000 revs down the Motorway!

Another point - Some rebuilders seem to end up with incredibaly stiff
engines - if whilst assembling it at any stage you cant turn the engine by
hand with just a bit of friction - stop and find out why - dont even begin
to try and start it up.

Clive
Nr. Oxford, UK

[Harry Pyle]

Hi Everyone,

The ultimate in guaranteeing instant oil pressure after new rebuild is to
1) assemble all parts with 'assembly' oil/grease.
2) prime the the pump with same as above.
3) fill the oil filter with engine oil
4) fill ALL the oil galleries in the block, head, rockers, crankshaft with
engine oil by the use of a bicycle pump or similar adapted to the oil
pressure guage fitting at the block. I have found that 6 bicycle pumps full
of oil will show oil coming out of the rockers at the top.(and you will hear
air/hissing and then oil/gurgling sounds from the crankcase....MUSIC to yer
ears)

At this stage you KNOW that you have oil in every conceivable gallery in the
engine and it is safe to startup without any chance of damaging
bearings/surfaces. There will be a slight delay in the guage reading as that
line will not yet be primed..but the total engine will have INSTANT
pressure.

This is what is called the REAL WORLD and was taught to me many years ago by
a farmer/TC friend by name of John Bowles.

Hope this helps.
Regards

Harry

----- Original Message -----
From: PMS GB Ltd
To:
Cc: [unknown] ; [unknown]
Sent: Tuesday, May 09, 2000 9:10 PM
Subject: Re: Re: [mg-tabc] Oil pressure


> Message text written by INTERNET:CFritz7001@aol.com
> > Betcha dollars to doughnuts that one or more of these precautions were
> not carried out on the fresh engine overhauls which resulted in ruined
> bearings on first start-up.<
>
> Hi Carl - Yes in each case the guy said he had had no oil pressure - just
> kept running the engine to find some and ended up scraping the dry
bearings
> to death. And as you point out, filling a vertical filter can certainly
> save 10 seconds dry running time.
>
> I always prefer to turn the engine over on the starter or by hand -
without
> the plugs in - to ensure I've got oil up to the rockers before firing up
> and giving it 5000 revs down the Motorway!
>
> Another point - Some rebuilders seem to end up with incredibaly stiff
> engines - if whilst assembling it at any stage you cant turn the engine by
> hand with just a bit of friction - stop and find out why - dont even begin
> to try and start it up.
>
> Clive
> Nr. Oxford, UK
>
>
>

[sculptart@aol.com]

To All,
My thanks to everyone that had suggestions on my odd oil pressure
problem. I will approach this from the gauge/tube/relief ball/etc. in order.
From the sounds of it, I have oil that has thickened or air is trapped in the
oil gauge line and there is no problem with the pump itself. This suits me
fine as my Scottish ancestry shows up whenever I have to lay out $ for more
parts!
Ben Cordsen, TC 4260