Pressure Fed Tensioner failed

timc · 12:48 PM

Drove the 930 down to Orlando this weekend for my daughters swim meet, and as I pull into the hotel I hear the classic rattling just off of idle. (Had several fail in early cars) So this morning I go out to the car, crank it up, no noise. After the swim meet I begin the 7hr drive back home, stopped after 2hrs, (no noise), 3.5 hrs (no noise) then after approx 5 hrs heard the rattling just off of idle. Funny thing is it takes a while for it to start making noise. I stopped on the way home at a friends house just to confirm. So I then shut the car down after we both agreed it was the dr side tensioner, and we talked for about an hour, then started it back up for the 30min drive home and no noise the entire way home.

This is my first experience with a pressure fed tensioner failure. Any way to rebuild/ clean? or do i just replace.

Friend was also telling me that Porsche updated the orifice on each of the two oil lines that supply oil to the tensioner to a smaller diameter for better pressure, so I'm wondering if that could help????

BReyes · BReyes's Garage

When they fail do they go intermitently, or go all at once? Is it normally something that can be heard before it fails?

Regards,

timc · 05-09-2008, 05:51 AM

Quote:

Originally Posted by BReyes

When they fail do they go intermitently, or go all at once? Is it normally something that can be heard before it fails?

Regards,

Thru the years, I've had 4 sets of hyd. tensioners fail, and they all gave warnings that they were begining to fail, usually rattling just off of idle. I've never had one fail completely, and I've driven 911's many miles over the last 25 years of ownership.

Now, regarding the pressure fed tensioners, this is my first. Mine has only made noise twice, both times after driving the car for more than 4 - 5 hours (same trip to Orlando), and only noisey just over idle, then they quiet down, (which is what I experienced in the hyd. tensioers). I've driven the car several times since, and they are quiet. This, I've never experienced, must be a characteristic of the pressure fed technology. I've ordered a new tensioner just to be safe. And mine is only the dr side that is "sometimes" noisey.

And yes, sure it could be something else, but with it not making anymore noise pretty hard to diagnose. But I've heard enough tensioners, that I'm pretty sure that's it. I'll replace the dr side and go from there.

A930Rocket · 05-09-2008, 06:57 AM

Just one? If you are in there, why not go with two?

timc · 05-09-2008, 08:07 AM

I don't know, Good point!

356-930 · 356-930's Garage

Quote:

Originally Posted by timc

. . . .Porsche updated the orifice on each of the two oil lines that supply oil to the tensioner to a smaller diameter for better pressure, so I'm wondering if that could help????

Smaller orifice in a hydraulic system of any kind will reduce flow and possibly pressure after the orifice.
If Porsche reduced the orifice on the fittings feeding the tensioners, it wanted them to have less flow, less pressure or both.

timc · 05-09-2008, 11:08 AM

Quote:

Originally Posted by 356-930

Smaller orifice in a hydraulic system of any kind will reduce flow and possibly pressure after the orifice.
If Porsche reduced the orifice on the fittings feeding the tensioners, it wanted them to have less flow, less pressure or both.

I'd sure be curious to know why? Better tensioner reliability or More pressure to other parts of the engine???

356-930 · 356-930's Garage

Quote:

Originally Posted by timc

I'd sure be curious to know why? Better tensioner reliability or More pressure to other parts of the engine???

Since engine oil pressure is regulated via a spring loaded bypass valve circuit that bleeds pressure over the spring's control pressure, the smaller orifice is most probably used to lower oil pressure in the tensioner.
We can't know Porsche's reasoning for the smaller orifice without asking but since engine oil pressure is otherwise regulated, the change was probably motivated by premature failure of the tensioner's oil seals.

NathanUK · NathanUK's Garage

This "mod" was talked about in the 911 section and very briefly here on the 930 section.

Do a search on the 911 section.

DonE · 05-26-2008, 07:36 PM

I had two fail just after the rebuild, but at different times. And the symptoms were exactly as you describe. I did the oil pressure valve shim mod and so far, all has been OK, so it seems as though low oil pressure at start is the culprit with mine.

sand_man · 05-27-2008, 06:33 AM

See post number 43:

http://forums.pelicanparts.com/showthread.php?threadid=199819&perpage=20&pagenumber=3

When I rebuilt my engine, I sent all of my parts out to "the old master" - Neil Harvey (Performance Developments) and had him do all the machine work and and reset all of the specs/tolerances on my engine parts. Anyway, I discussed this mod with him, as I have heard about many pressure fed tensioner failers. Something that I worry about, especially since my car is daily driven. Neil rebuilt my factory hydro-tensioners (they only had about 40K on them) and didn't think I'd have any trouble. I dunno, next time I have my chain covers off, I'm tinking about doing it.

DonE · 05-28-2008, 07:13 PM

I called Neil Harvey today and told him about the problem. Even he stated that he uses the carrera hydraulic tensioners on race motors and has not had one crap out in a very long time. He said one of a couple things is going on: chain is worn (too long) or the cam center to crank center has been shortened somehow (shaved heads, new cylinders, etc). So, he offered to make me a couple of hardened steel caps to go over the tensioner pistons in order to put greater tension on the chains. Although my chains seem taught, I think the tension could be tighter. The only other option is to use mechanical chain tensioners - which I am OK with since I would use the race tensioners made by JB Racing. Let's see....

sand_man · 08:23 PM

Quote:

Originally Posted by DonE

I called Neil Harvey today and told him about the problem. Even he stated that he uses the carrera hydraulic tensioners on race motors and has not had one crap out in a very long time. He said one of a couple things is going on: chain is worn (too long) or the cam center to crank center has been shortened somehow (shaved heads, new cylinders, etc). So, he offered to make me a couple of hardened steel caps to go over the tensioner pistons in order to put greater tension on the chains. Although my chains seem taught, I think the tension could be tighter. The only other option is to use mechanical chain tensioners - which I am OK with since I would use the race tensioners made by JB Racing. Let's see....

Yeah, I recall him mentioning that to me about the use of hydraulic tensioners in some race engines.

Of course a race engine, that is subject to regular tear downs and scrutiny, can easily get away with the meachanical type.

Being that I'm always into my engine, I'd probably be okay with the mechanical ones too...a lot of shops make a good argument for them.