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100M starts to drink oil..................

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356roadster

356roadster

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I had a great tour through the swiss alps on the weekend with my 100M which had a full engine rebuilt 9000mls ago (but: this was in the 80s..... the car was sitting in a collection then for a long period afterwards). the tour was a great experience we have passed a lot of scenic routes and towns like st.moritz, klosters or davos..... the car performed well; perfect oil pressure, perfect water and oil temperature, perfect alfin drum brakes. it was a sheer pleasure....

but: :crazy:

the car needed lot´s of oil (around 2 litres for 1000kms) but there is no blue smoke, only the normal leaks (which we all know) and also no other bad signs (no oil in the water etc.).

Now I don´t know what to think about this??? It never consumed so much before and I had a new oil service (20W50) before starting to switzerland.

Do you have any ideas how to proceed now???

Thank you for your recommendations!!

Wolfgang
 
Hello Wolfgang,

I did not have special experience in 100 M engines. But I have some ideas which way the oil can gone...the way over the valve stem seals( only an o-ring) and over the piston oil seal rings. Do you know your oil specification is really 20-w50 ? (mineralisch)
But I hope for you , the crank case ventilation is the reason of your challenge. Check the way from the valve cover to the area of the sucking access. Is the way completly open or closed and you have some missing deflector sheets or metal spongs?
Or a new AL-valve cover with no deflector...
If there is all ok ,I would change first the stem seals....
Did you check your compression parameters, with and without oil filling in the spark plug holes ? This is only to get a feeling for your cylinder condition.

I hope the best.


Yours Michel- who lives near Frankfurt
 
I'm not familiar w that particular engine...

BUT I'd be looking for excessive venting of oil, OR leaking past valve stem seals or piston rings. MIGHT be just enough of a leak to consume oil, but not enough for you to notice blue smoke.

2 Liters does seem like a lot of oil... What does the bottom of the car look like? Any signs of oil being sprayed on the underside?

I had a Jag E-type once where the previous owner had reversed the crankcase ventilation hoses. Blew oil EVERYWHERE!! Got so bad that I could barely see cars behind me!! This was on a cross-country trip right after purchase.... After MANY stops and refills we finally gave in and put the car on a trailer for the remainder of the trip. This saved the engine, but blew the initial purchase/transportation budget. "Oh Well!"

I had a Ford F-250 Pick-up once that drank about a quart of oil w every fill-up of gas. Never saw any smoke, but oil kept "disappearing". Turned out to be bad valve stem seals.

As mentioned above, check the compression, check the crankcase ventilation.

Good Luck! :cheers:
-Bear-
 
356roadster said:
the car needed lot´s of oil (around 2 litres for 1000kms) but there is no blue smoke, only the normal leaks (which we all know) and also no other bad signs (no oil in the water etc.).

Do you have any ideas how to proceed now???
Wolfgang
Click to expand...
One of the most common causes of this problem is worn rocker arm bushings.

With the cover removed & the engine idling, there should be no more than a drip about every two seconds from any individual rocker arm. These engines do not tolerate excessive oil flow down the valve guides/stems.

A steady stream, or heaven forbid, an oil gusher would indicate the need to rebuild the rocker arm/bushing assembly. Not as easy as it would first appear. Some replacement bushings do not have their slots in the correct places & can make the problem worse.
D
 
Thank you for all your recommendations. I have checked the compression yesterday evening and the instrument has shown between 11,5 and 12,5 bar at the single cylinders which - in my opinion - is more than adequate. So I do not have worn cylinders as it seems.

I will check Dave´s recommendation concerning the rocker arms this evening and will report again.

The only thing I did not understand well is how to check out the crankcase ventilation. Could anybody explain how to proceed there???

Thank you again, Wolfgang
 
The crankcase ventilation consists of a road draft tube exiting the side cover on the left side & a baffled vent from the tappet cover to the air intake.
D
 
Wolfgang, just a thought, on the oil change recently, do you know who did it?

Did they know that these cars take lke twice as much oil as most modern cars? maybe it wasn't filled properly in the first place.

Two liters is a lot of oil, it is hard to lose that much without a visible sign, also my motor seemed to have some blowby--oil leak issues until the rings were fully seated after and engine rebuild, maybe a blowby/crankcase pressure issue.
 
Hi Dave,
thank you for your explanation. I already found the tube on the left side cover. I can take it off and check whether there is any dirt in it.
I am so sorry but I cannot understand the second thing (baffled vent...). Can I see this thing on any drawing in a catalogue or so????
Sorry again for my bad english and thank you so much for your help!!!
Wolfgang
 
Dave's reference to the baffled vent is I believe is the one in the valve cover I believe, this should be a little metal extension coming out of your valve cover which will have a rubber hose attached to it going to the carburators--it is baffled on the inside of the valve cover.

If you have an aftermarket valve cover you may or may not have the vent.
 
Hi Glemon, thank you for your explanation. Now I know what is meant. The metal extension ist there and there is also a rubber hose to the col air box. My valve cover is aftermarket and it is not baffled on the inside; I hope that this is no problem. Sorry again for taking part in the forum with a bad technical english like mine....

Dave, I have checked the oil-flow coming from the rocker arms. I think that you are completely right: This seems to be the problem. There is a slow but steady flow form every rocker arm at idling revs. The flow looks very equal on every rocker arm. I am not so clear about the problem which results from this.... I assume that the oil flow is too much at normal driving revs and the oil is looking for a way out as the normal way through the valve guides/stems is not sufficient for the capacity which has to pass. Right? But what happens then? Does the oil come out through the crankcase ventilation or what happens next??
 

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Dave,

another thing: Would it maybe be possible that my engine has too much oil pressure?? Can this lead to the steady flow coming out from the rocker arms?? As I have learned the oil pressure at the 100 engine should be around 50psi at 3000revs; mine is between 60psi and 70psi when warm. If this could be the problem: Are there any adjusting possibilities to bring back the oil pressure to a normal level??

Thank you again, Wolfgang
 
The basic problem is that the oil must drain back down to the sump via the very limited areas round the pushrod clearance holes in the cylinder head. The normal way. Excessive oil tends to flood the valve stems if it can't drain down fast enough. The simple o ring valve stem seals cannot withstand much excess oil flow.

Higher than normal oil pressure, I would say 60 psi maximum, could increase the problem somewhat but would not be the sole problem. This pressure is somemhat adjustable by changing the relief valve tension.

Someone asked earlier, SAE 20-W 50 oil is used by many Healey folks.
D
 
Dave,
thank you for your answer. So the next step will be to lower the tension of the relief valve a little bit and see what happens to the oil flow on the rockers. If this will not cure the problem - which is obviously very likely - I will have to put in new bushings. I will report again as solving the problem could maybe also be interesting for other members.

What I am also wondering about is that there is no blue smoke from the exhaust if the problem is that the o ring seals cannot withstand the oil flow? According to my understanding there should be blue smoke in the is case. Right?
 

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I don't know how you could be losing that much oil from excessive valvtrain seepage wirhout seeing either blue smoke (may no appear or get too bad until the car is pretty warm) or seeing it leaking down the block somewhere.
 
I think you need to recheck your observations/assumptions.

If the engine really is using that much oil, it has to be going somewhere.

Into the combustion chambers & out as blue smoke

Into the cooling system

Leaking out various locations to the ground

Someone is playing jokes on you

It cannot just evaporate into thin air
D
 
Your engine unknown to me but changing the rocket gear on my '63 BJ7 made an incredible improvement to both oil consumption and overall pressure (10/15 psi). Mine, prior to change, resembled a row of mini waterfalls : the 'new'' one ( I installed a reconditioned) bothered me on initial startup because there were only dribbles apparent --- I wondered if the was any oil there at first!!
 
I agree with Dave, maybe the best step at this time is to make sure oil is topped up, wipe any evidence of leakage/seapage you can get to off the motor, and monitor oil use, leakage, or any other evidence of use such as blue smoke.

These engines have relatively huge sumps and you have to lose a lot of oil before you run into any sort of oil supply/lubrication problems, so as long as you are monitoring it you should be OK.
 
Dave, John, Glemon,
thank you for your comments. It´s so helpful especially for a technical novice concerning the 100 engine like me. Based on this I will do the cleaning job on the weekend, top up the oil and do a longer drive to see where oil is coming out. I will report again....
I wish all of you a very nice weekend!
 
I occasionally use a "black light" oil tracer system to pinpoint hard to find leaks. These tracer systems are readily available from many auto supply stores & vary from quite cheap to more elaborate.

All external leaked oil should be as throughly removed as possible. Very important.

A small quantity of chemical would be introduced into the engine crankcase oil.

A typical low cost system would use a 12 volt, 50 watt detector light in conjunction with contrast enhancing glasses. It probably still should be viewed under low ambient light conditions to get maximum contrast.

It's surprising how many times the leak is originating from a completely different location than you might imagine. It is frequently only necessary to only run the engine on jack stands to spot the leak origin. If you drive the car, it's likely to just spread the leak around & make the source less distinct.

The same method can be used to spot leaks of the transmission oil.
D
 
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