Zero oil pressure at 4000 RPM

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Jurjen

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• Apr 17, 2018

• #1

Is it in any way possible a broken piston pin circlip can stop the oil circulation and cause a 100% drop of oil pressure when driving at 85 MPH?

(Edit) Some details:

- Freshly rebuilt MK3 engine; 4,000 miles driven
- Sudden loss of power driving at 80 - 90 MPH / 3,000 - 4,000 RPM
- Zero oil pressure on gauge at 80 - 90 MPH / 3,000 - 4,000 RPM
- After cooling down, the engine still ran (oil pressure was up, but lower than normal)

After pulling the engine:
- Piston/gudgeon pin circlip 2nd cylinder broken (see pictures)
- 2nd cylinder damaged
- All bearings worn (bearings at 6th cylinder show the most wear - 1st cylinder bearings - main and rod - look ok)

I'm trying to find out what happened, because I don't want to pay for a new rebuild.

 

Last edited by a moderator: Apr 21, 2018

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bob hughes

Luke Skywalker

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• Apr 17, 2018

• #2

Re: Zero oil pressure at 4.000 RPM

I guess that it could depend on where that broken piece ended up.

That is extremely unlucky.

The real question is why did it break? Installed correctly - there should be very little stress on that part.

Have a look inside your oil pump and see what the parts look like, the strainer should have stopped anything large from entering, have you found all the bits of the circlip?



Bob

 

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Jurjen

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• Apr 17, 2018

• #3

Re: Zero oil pressure at 4.000 RPM

No, I didn't find all the bits and the strainer was on the pump.

Nobody knows why the circlip broke, but the engine builder will repair the damage to the piston and cylinder free of charge. The damage to the crank though, I have to pay myself because it's uncorrelated, supposedly. I know next to nothing, but have some doubts.

For me, this is about finding an argument to convince the builder there is a scenario where both issues are correlated.

 

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dancrim

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• Apr 17, 2018

• #4

Re: Zero oil pressure at 4.000 RPM

Sounds like that motor got too hot. 2 reasons for that: Water pump failed or oil pump failed. Either
would cause crank bearings to start to seize and act like a loss of power. Pistons become too tight
in the bore and this can cause the clip to pop out. Be sure to check the oil pump for a sheered gear key.
Can you be sure the pump didn't loose pressure just before the power loss. At 85 we normally don't
have our eyes on the gauge and it would only take a minute to seize things up.

 

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Jurjen

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• Apr 17, 2018

• #5

Re: Zero oil pressure at 4.000 RPM

Thanks for the replies!

Yes, the dip of oil pressure could have well happened just before the loss of power. It was only after the car slowed down, that I looked at the gauge and stopped the car.

The engine getting too hot is another scenario. But it’s hard to say what caused it to overheat at that moment, now the engine is out. The 2,500 miles in summerly Italy before the breakdown were without any heating problems.

The oil pump is still looking good by the way.

And the cylinder was badly damaged by the circlip. I don't know how long it takes for that to happen?

 

Bob_Spidell

Yoda

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• Apr 17, 2018

• #6

Re: Zero oil pressure at 4.000 RPM

Is that excessive carbon buildup on the piston (asking because I don't know, but wouldn't expect that on a low-time engine)? Would that be a clue?

 

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Jurjen

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• Apr 17, 2018

• #7

Re: Zero oil pressure at 4.000 RPM

Good question, I don't know whether it is excessive.

On this piston (the 2nd) the carbon was partly washed of, due to the head gasket being blown after the overheating/breakdown. Altogether I have driven the car for 100 miles after that (on different occasions, trying to figure out what was the problem).

 

Last edited: Apr 17, 2018

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bob hughes

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• Apr 17, 2018

• #8

Re: Zero oil pressure at 4.000 RPM

Jurjen said:

Altogether I have driven the car for 100 miles after that (on different occasions, trying to figure out what was the problem).

Click to expand...

That would not have helped matters at all I am afraid.



Bob

 

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dancrim

Jedi Hopeful

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• Apr 17, 2018

• #9

Re: Zero oil pressure at 4.000 RPM

As a note, you might want to get caps that fit into the piston pin holes
as a safety measure. Not sure if they replace the clips or are just to
prevent damage if a clip fails. Man, that engine did overheat. The
head will have to be checked and possibly be resurfaced. I once had
a motor act the same many years ago. After cooling it started. Turned
out to be a overheating problem but I forgot if it was the water pump
or not. Luckily I stopped before any real damage was done. Once the
motor is at operating Temp. it would only take a mile to lock it up.
By the way, I worked for Philips many years and had to travel to
Eindhoven quite a few times. Good luck with your motor.

 

Bob_Spidell

Yoda

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• Apr 17, 2018

• #10

Re: Zero oil pressure at 4.000 RPM

Here's a couple photos of 2 pistons removed from my BJ8 engine at overhaul (one was cleaned-up for inspection). These pistons had about 100K miles on them since a prior overhaul, and they probably had about 150K miles total (I don't remember if we cleaned them up when we reused them). So, the carbon buildup on yours may not be excessive:







I vaguely recall when we did the first overhaul the pistons had a lighter-colored, dry-appearing coating on top that didn't have the dark, oily appearance of these. But, at that time I was still running on mostly ethanol-free gas.

 

Patrick67BJ8

Obi Wan

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• Apr 17, 2018

• #11

Re: Zero oil pressure at 4.000 RPM

If you checked your oil pump and it’s good I’d check the oil pressure relief valve next.

 

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Jim 58 BN6

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• Apr 17, 2018

• #12

Re: Zero oil pressure at 4.000 RPM

Patrick67BJ8 said:

If you checked your oil pump and it’s good I’d check the oil pressure relief valve next.

Click to expand...

That's a really good idea. About 40 years ago, I was flying down Interstate 280 just south of San Mateo/Belmont, in my original TR4 . The oil pressure suddenly went to zero. Fortunately, I saw it and shut the engine down and coasted to the shoulder. I found about 1/4 of a rather large (~1" dia) internal tooth washer blocking open the pressure relief valve (kind of similar to part of a piston pin clip??). It looked like nothing I remember seeing when I had put the engine together from a box of parts about a month before, and I had just driven the car from Northern New Mexico to the Bay Area. At least it didn't happen in ELY, NV! I reassembled the valve, the oil pressure came back, and I never had that problem again. I never did figure out where the 1/4 of a washer came from.

Good luck getting your car sorted out and back on the road.

 

Michael Oritt

Yoda

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• Apr 17, 2018

• #13

Re: Zero oil pressure at 4.000 RPM

Jurjen--

Naturally we are only able to speculate on what happened but if I understand post #7 correctly the fact that you have operated the engine for an appreciable amount of time since the incident is going to make it very hard to reach a definitive answer as to what failed first, etc. etc. I could be very wrong but I'm with dancrim when he says that the circlip's becoming dislodged was a result, not a cause.

 

BigGreen

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• Apr 18, 2018

• #14

Re: Zero oil pressure at 4.000 RPM

Jurjen said:

... For me, this is about finding an argument to convince the builder there is a scenario where both issues are correlated.

Click to expand...

Jurjen said:

... Altogether I have driven the car for 100 miles after that (on different occasions, trying to figure out what was the problem).

Click to expand...

Not a good combination.

Was the builder a Healey expert ? Thought about a second opinion by one of the builders known by the AHOCN ?

 

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Jurjen

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• Apr 18, 2018

• #15

Re: Zero oil pressure at 4.000 RPM

No, not a good combination at all. But after the breakdown it was serviced by a respectable mechanic who couldn’t find anything unusual. It was only after 100 miles of strange behavior (as the owner, you know when something is wrong) I thought it best to pull the engine. I spoke to a lot of connoisseurs about this, including some AHOCN people.

But alas, thanks for all the reactions; I think I have my answer: bite the bullet, pay the bill and drive the car.

I've learned so much the past few months, whatever it was that caused the failure, it won’t happen again.

Or will... I don’t know. But in that case, I’ll repair it myself!

 

Michael Oritt

Yoda

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• Apr 18, 2018

• #16

Re: Zero oil pressure at 4.000 RPM

What happened to Jurjen might have been prevented by a prominently-displayed "idiot light" wired to a normally-open 5-10 psi switch plumbed into the oil flex line.

Warning lights got a bad rap when manufacturers tried to do away with or marginalize gauges. However when the OP gauge is not prominently mounted in our line of sight, as is the case with the "Safety Gauge" supplied on our cars, it is easy to miss seeing the needle plunging to zero or waivering as bearings fail/spin, etc.

Because I have a Smitty's five speed the hole for the OD switch offered me a great place to mount such a light and though it is below my line of sight it is big enough to be in my peripheral vision and catch my eye. I know many owners are averse to drilling holes in their dash fascias and there are other options. In any case the stakes are high as this topic demonstrates.

 

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Jurjen

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• Apr 18, 2018

• #17

Re: Zero oil pressure at 4.000 RPM

That's actually the first thing I will do when I get the engine back. Install an oil pressure switch and drill a big hole right next to the indicator light.

 

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dancrim

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• Apr 20, 2018

• #18

Re: Zero oil pressure at 4.000 RPM

The "idiot" light is a "better" but a sonar alert is best. Emits a high pitched sound.
Again, will you notice a light going on when driving? Especially in the summer sun?
If the sonar alert goes off, you WILL notice it. They are cheap, 12v. and as easy
to wire as a light. Again, I see you tested the oil pump, be sure you keep a good
eye on the Temp. gauge as well once you run the car.

 

GeorgeC

Member

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• Apr 21, 2018

• #19

Re: Zero oil pressure at 4.000 RPM

Will these sonar alerts work with positive earth?

 

steveg

Yoda

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• Apr 21, 2018

• #20

Re: Zero oil pressure at 4.000 RPM

dancrim said:

The "idiot" light is a "better" but a sonar alert is best. Emits a high pitched sound.
Again, will you notice a light going on when driving? Especially in the summer sun?
If the sonar alert goes off, you WILL notice it. They are cheap, 12v. and as easy
to wire as a light. Again, I see you tested the oil pump, be sure you keep a good
eye on the Temp. gauge as well once you run the car.

Click to expand...

How about a link? All I could find was OEM switch replacements. Will they work if attached to a 12V buzzer?