Do I have a bad tensioner????

[mr914]

Greetings,

I purchased a 74 911 Targa, 2.7 Cis last december with 84,000 miles.

The previous owner had done a tensioner update at about 79,000 miles. He drove the car about 6,000 miles in 14 years. Always used Valvoline 20-50 racing oil and basicly let the car sit 9-10 months out of the year.

When I bought the car. There would be a loud banging for the first 30 seconds when the car was started cold. I first thought that it was motor mounts (3/8" play in the mounts and 3/8" clearance between the muffler and valance panel) and I replaced them. The noise continued but now not as pronounced and only when the car was cold.

Oil pressure? I noticed that when the engine would start, the oil pressure would be in the 80-100 range and when the noise stopped the pressure would be 140psi.

At the recommendation of a long time porsche mechanic, I tried CD-2 and rislone. The noise at startup became occasional. Once every 10-12 cold starts.

Well, I changed my oil, 20-50 non-synthetic. Ran a couple of DE events at Waterford Hills, where my oil temperature hit 240-250. Still has the loop cooler in it and no missed shifts or over-revs.

Now when it starts, I get the banging for a few seconds and then a new noise from the engine.

I've never heard a chain dragging from a collapsed tensioner, but that is what I think I am hearing.


Wayne, Love your 101 Projects book! How about adding some sound files to your website to aid in diagnosis.... Pulled head stud, Flashed cylinder, timing chain... Plus some of the good sounds 917, 935 wastegates

Well, I'm planning on dropping the oil, pulling the sump to inspect the screen, check adjustment on the valves.

Do you think I should pull the cam covers to inspect?

[Early_S_Man]

You have to pull the muffler and the chain case covers to check the tensioners, and, yes, you are several months overdue on THAT check!

[rstoll]

Could be as simple as a broken chain ramp too. Pull the chain covers and check it out, TODAY!

[mr914]

The 911 is up on jack stands and the oil is draining. As soon as it cools off, I'll roll my sleves up and tear into it.

[Kemo]

mr914,
I am saving up for the tensioner kit as we speak. I had similar noises and sure enough, my passenger side tensioner had collapsed. Please post some pics, if you can.

[Wayne 962]

It's really tough to describe noises. Post a .wav file, and let's listen?

-Wayne

[rstoll]

Any updates?

[mr914]

After a mishap, which resulted in stitches in my knee

Pulled the sump screen - Nothing in it

Pulled the valve covers and adjusted the valves - A couple were loose by a couple thou...

Pulled the muffler - found where the muffler was contacting the rear tinwork.

Pulled the chain covers

Found that PO mechanic uses some form of gasket compound when installing...

Left tensioner - can't move by hand when pushing/pulling on idler arm.

Right tensioner - can move tensioner about 1/8" on shaft when pushing pulling by hand.

Took tensoners out - found that 2.5mm allen wrench works as a sutible retaining pin. and put them back in after reading the 101 projects book.

Checked play between tensioner and idler. Left one has about .050" play and the right one has .100" play.

Aparently, I have the early idlers. But, can anyone post the measuremens of the widths of the new idler arm????

The sprockets show some wear and there are pits on the left shaft.

I have not checked the ramps yet.... Tomorrow morning... 007 is on in HD

[Early_S_Man]

That sounds like two bad or worn out tensioners to me! With the locking pin pulled out ... there should be ZERO clearance between tensioner plunger and idler arm ... and the tensioner should be exerting significant force against the idler!

[mr914]

When installed, there was Zero clearance between the tensioner and idler.

When I pushed on the right idler by hand, I was able to move it about 1/8", then it would return to normal.

Shall I interpet that significan force, means that I cannot push the idler in by hand at all?

Anyone have a set of calipers and a new style idler arm handy?

I sure could use the widths of the flanges that go around the shaft to determine if I have the old or new ones.

I have the tensioners out on the bench now (with pins in). I'll chock it up in the vise and see what I have.

I seem to remember reading somewhere about sticking check vavles in the tensionsers, but, I can't seem to find the post. I think the tensioners releived @ 14psi.

[mr914]

I have the tensioners out on the bench now.

Each one the rod can be depressed between a 1/4 and 3/8 of an inch by hand.

They had been cycled a few times while I found out what size of pin to use to retain the piston. So I am fairly sure that there is no oil in the tensioner.


Sounds like I should replace them?

[Wayne 962]

These tensioners have become very confusing. Just because you can compress them with your hand doesn't mean that they are bad - it just means that they have had the oil bled out of them. If you pump them up while they are submerged in oil, then they will tighten up to the point where you will need a vise to compress them again. I have done this with new tensioners, and good used ones too.

As for noises when your car is warming up, there are many different noises that can occur when the engine is cold. It's not uncommon for a brand new engine to make semi-suspicious noises when warming up. Unless it's really loud, or scrapping, then I wouldn't worry too much about it. These engines can expand up to an eighth of an inch width-wise from cold to warm. That's a pretty significant distance, and can cause the engines to run not too optimally at cold temperatures. The 911 engine is a strange breed sometimes and cannot be governed by convential engine wisdom...

-Wayne

[Kemo]

This is a pic of my stock tensioner, and it is dead.

[Early_S_Man]

HEY, 914! Before masking the decision to replace them ... try pumping up/bleeding them is a pan of oil by hand. If they stiiffen-up as Wayne described ... they probably are still OK!

[FRED/LI]

When everything's in place, push hard on the tensioner end of the left idler arm and see how close it comes to the chain housing. This is essentially causing the same action as a fully extended tensioner. If your chain is worn, the arm can, at times, make contact and cause a rapping similar to the collapsed tensioner as the chain goes through a cycle.
It's worth checking before you close her up.

[Ned, NYNA 11]

Mr 914,
Get a set of ear plugs and 2 containers for the oil dribble. Install the tensioners and place the containers to catch the dribble. Small from the drivers side, negligible from pass side. Spin up the engine with the coil grounded to get oil pressure up. Connect the coil and start the engine while observing the tensioners. Note that the spring in the tensioner should be stiff enough to keep the plunger extended such that you cannot depress it by hand. Oil pressure adds to the force on the plunger but it's real job is to dampen the movement of the plunger, that is to hold it steady.
Get the help to vary the speed of the engine and watch the action at the tensioners. If they all are tight especially when you drop speed suddenly on the engine, you are fine. If the sprocket is not hard tight against the chains you need new tensioners.
Ask me how I know all this. Ah, got a couple of used tensioners in the garage. The new ones I installed were just as good as the couple I replaced.
Ned Monaghan

[mr914]

I'll give the tensioners the submerged oil test tonight.

ALA - As Long As...

I ordered the later style idlers and 2 new sprockets from Pelican on Wednesday AND there here at my door on Friday. Good Job Wayne.


I pulled the old idlers out and installed the new sprockets on the new idlers. The sprockets seem to be tight in the idler???

Put the new idlers in (with oil) and pivioted them. Seems that the right one has a momentary bind in it, almost like a notch. Pulled the idler back out and looked at the shaft. Found rust pits on the shaft.

Could that have been causing my noise??

[mr914]

Bummer, does not look like the idler shaft is a replaceable part.

Looks like it comes with the chain housing.

What about deburring it with a polishing wheel on a dremel?