Never ending problem for the 13th engine rebuild (very long post)......

[boyt911sc]

Originally Posted by Sub8

Oil pressure hot or cold? Was 30psi measured whilst your problem tapping was occurring?

James,

The engine oil temperature was not really hot because I did not run the engine long enough to get to operating temperature. But the very initial test run was long enough to make the engine hot and it sounded OK. But afterwards, I noticed the loud tapping or knocking noise coming from the motor. Since I did not have a pressure gauge installed at that time, it was not known if I had sufficient oil pressure.

I have installed a mechanical pressure gauge and tach to monitor the oil pressure and engine speed respectively. And the 'noise' is very noticeable and discouraging. The nagging question I have is what is the culprit causing this anomaly? At this point, I have no idea except to seek advices from the experienced people to share their thoughts. And do the investigation for the suggested 'culprit'. So far, I have not located nor identify the culprit. The investigation is on going.......case folder is wide open. Thanks.

Tony

[Sub8]

Well as the oil heats it's viscosity drops.

Potentially a bottom end problem with mains or bigend bearing might not be audiable until oil viscosity and hence effective pressure drops?

What about high leakage from the hydraulic tensioners, this potentially would also be worse with hot oil vs cold.

You would think a knock due to worn woodruff key would be there from cold? I would think worn little end bearings would also be noticeable from cold.

[boyt911sc]

Originally Posted by Sub8

Well as the oil heats it's viscosity drops.

Potentially a bottom end problem with mains or bigend bearing might not be audiable until oil viscosity and hence effective pressure drops?

What about high leakage from the hydraulic tensioners, this potentially would also be worse with hot oil vs cold.

You would think a knock due to worn woodruff key would be there from cold? I would think worn little end bearings would also be noticeable from cold.

James,

Oil viscosity is a function of temperature. The chain tensioners will be tested. Last time I looked at the tensoiners they were stiff and have not collapsed. That's one reason I want to run with mechanical tensioners. I agree with your evaluation. Some of these could not be checked without an engine teardown which eventually will happen soon.

Now, that I am more aware of the problem, the slapping/knocking/tapping noise is noticeable even with a cold engine (?). I have listed down the suggestions given in this thread and consider each and everyone as important as the others. But some of the tests prior to tear down could be done soon. Thanks.

Tony

[911 tweaks]

if eng is in car, which I think it is, so it can b started, i would trailer the car to speciality cars in allentown,,, call em to set up a time u can swing the car by so they can listen and give you their opinion... call them at 610 437 9333... ask for mark burkett the owner and one of the most knowledgeable porsche eng builders around... tell them bob at design assoc told you to call them... and yes i do know mark and all the people at his shop... as honest as the day is long... good luck... my opinion is a tear down and inspect & measure everything... good luck tony...

[Alan L]

Tony, Try the simple stuff first. Check the fan is not binding, the pulley is tight etc.
Alan

[boyt911sc]

Originally Posted by 911 tweaks

if eng is in car, which I think it is, so it can b started, i would trailer the car to speciality cars in allentown,,, call em to set up a time u can swing the car by so they can listen and give you their opinion... call them at 610 437 9333... ask for mark burkett the owner and one of the most knowledgeable porsche eng builders around... tell them bob at design assoc told you to call them... and yes i do know mark and all the people at his shop... as honest as the day is long... good luck... my opinion is a tear down and inspect & measure everything... good luck tony...

911 tweaks,

I personally know Mark Burkett for many years and have been in his shop numerous time. The engine is not installed in a car but mounted on my engine test stand. Never occurred to me that I could bring the engine test stand with the engine. The whole assembly is on large caster wheels and no problem getting the engine test stand plus engine on my Trailex. Great suggestion!!!!

However, there are several good Porsche shops much closer to me than Mark's shop. This would be a good fall back to consider. Thanks.

Tony

[boyt911sc]

Originally Posted by Alan L

Tony, Try the simple stuff first. Check the fan is not binding, the pulley is tight etc.
Alan

Alan,

I already did the alternator fan belt removal test earlier and the noise was still there growling. Thanks.

Tony

[Alan L]

Long handle screw driver test. it seems you can run the engine on the stand?
Alan

[faapgar]

Hi,give me a call today and I will come and listen to your motor.Fred Apgar

[boyt911sc]

Originally Posted by Alan L

Long handle screw driver test. it seems you can run the engine on the stand?
Alan

Alan,

This home-made engine contraption was originally built for my CIS troubleshooting to have complete access all around the engine. Tach and oil pressure gauges installed only 2 weeks ago. A second test stand is on the drawing board and put on hold until I sorted this nagging engine noise dilemma.



BTW, I have a mechanic's stethoscope that does a good job for vibration and tapping noises. Thanks for the suggestions.

Tony

[boyt911sc]

Originally Posted by faapgar

Hi,give me a call today and I will come and listen to your motor.Fred Apgar

Fred,

I left a message on your phone and will PM you. Thanks.

Tony

[txhokie4life]

I had an engine tapping noise on a Boxster rebuild -- drove me nuts.

Tried to find an app that would listen to the tap and tell me what the frequency of the tapping was so that I could calculate bottom or top end.

We eventually found it the hard way -- a wrist pin was loose and clicking against the cylinder wall.
It eventually separated -- what a mess -- expensive tuition that day....

Thats not relevant -- but I was wondering if anyone did find something (reasonably priced) that could listen to a rhythmic sound and measure the frequency.

Mike

[VFR750]

Tony, yes the gear that is press-fit on the front of the crankshaft. It uses a fairly precise woodruff key to hold timing. My gear, over the years loosened up. Wore the crankshaft. Most people I talked too said that was not common, but with 32 years and lots of track time maybe inevitable?

Install the mechanical tensioners and eliminate one possible issue. Racers use mechanical tensioners because they rarely fail. They rebuild often enough that any gradual wear is readjusted during the next rebuild.

If you do this, any issue with the hydraulic tensioners will be eliminated.

[VFR750]

The ticking sound was coming from the front and was very hard to tell what was wrong.

Sound resonates on flat surfaces. The chain housing could be transmitting sound energy that is emanating from somewhere nearby.

Only after my crankshaft was inspected was the issue discovered. Gear has to come off to confirm it.

It was repaired and the sound disappeared.

That was a $800 "learning experience"

[smarens]

ok just read the whole thread, don't give up Tony you will find it and now I really want to know what the issue is, good luck hope you solve it soon

[boyt911sc]

Originally Posted by faapgar

Hi,give me a call today and I will come and listen to your motor.Fred Apgar

After my morning breakfast, I picked up my IPad and read my emails and proceeded to visit the PP forum like a daily ritual. Then saw the above post by Fred Apgar. And for those of you who are following the ups and downs of my 13th engine rebuild know that I have been struggling to determine the root cause of this annoying problem (knocking/slapping/tapping noise from the engine). I met Fred last week when I went to visit his garage to look for the slant nose fenders he is selling. I had no idea who this guy is except that he lives in Costa Rica and comes and visits USA a few times a year. And I thought, he could be one of the many affluent Americans living in this tropical paradise.

When I arrived at his garage, we exchanged greetings and introduced ourselves. I was interested in the slant nose he is selling that I am buying for an acquaintance. He walked me around and showed some interesting cars including the the car he is doing the engine rebuild in a few weeks schedule. That caught my attention that he does engine rebuild like a daily chore. It takes me months if not years to complete an engine rebuild.

In my desperation to solve my nagging engine noise problem, I mentioned to him about this 13th engine rebuild debacle. I was hoping he could give me some directions and to my surprised he got interested and gave some very specific instructions. He mentioned his trip to Philadelphia City and might swing by to look at the problematic engine. In the meantime, I decided to do some investigation by measuring the valves to piston clearances as suggested by some PP consultants (people I communicated via email or phone). To do this check, I have to remove the engine and put it on an engine stand. Drained the oil and some disassembly.

Back to the main story. I called Fred and left a message this morning (Tuesday). And sent an email informing him that tomorrow (Wednesday, doctor appointment and baby sitting), and Thursday or Friday would be good for me. An hour later he called me and told me he was available and would be coming to my place in 3 hours. The big problem was that the engine was not installed on the engine test stand and partially disassembled. Quickly and hurriedly picked up the engine up and installed it back on my engine test stand, connect oil lines, pour oil, etc. and finally a quick shower. Dressed up and jumped into my car to meet and pick up Fred at a local dinner I have never been before.

So we drove back to my place and had some car talks. I forgot something, he was carrying a mechanic stethoscope and pack of cigarettes. Got to my place and showed him the 'patient'.



Synopsis:

Without wasting any precious time, he asked me to start the engine and put on his stethoscope. I started it and it ran but I quickly turned the engine off. I could not bear to hear the noise and he instructed me to keep it running!!!! After a few minutes I stopped the engine and observed for his reaction. He instructed me to remove the left side chain housing cover to inspect the hydraulic tensioners.

I was so excited that my hands were shaking and could not remove the nut and washers from the chain housing cover. Fred took over and did the removal by himself. And the next thing I heard was 'you have a failed tensioner'. He lit his second cigarette and prepared to leave.

I told Fred that I have suspected the tensioners but I misdiagnosed it when I inspected the tensioners not once but twice. And I was thinking of installing a mechanical tensioners for a short test run. Now that the culprit has been identified and confirmed, I feel relieved and happy to proceed to the next stage.

BTW, Fred is a retired Porsche mechanic and took an early retirement at the ripe age of 52. He lives in Costa Rica and regularly visits USA to do some work and help his old clients.

Yesterday, I was desperate and confused. Today, I feel blessed and fortunate to meet the right person at the right time. After I took Fred back to our rendezvous, I was talking to myself while driving back home saying "perseverance and motivation" are the main characters in this story. Moral of the story: Do not quit, do not give up, help is available in many different ways and forms.

Tony

[Rich76_911s]

Tony,

Fantastic story! So glad you guys found the culprit. Hopefully this puts the 13th engine build in the books permanently! When I get to engine #13 I'm just calling it #14.

Cheers
Rich

[DRACO A5OG]

Outstanding!

[Rawknees'Turbo]

What a great read (post #98 especially, buttofcourse!) and outcome - nice!

[kenikh]

Made my night! Congrats.

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