Tensioners broken or am I weak?

[Sam1905]

Me again - why don't you all just come to my house and lets do this together..would save a lot of typing!

I am trying to refit my chain tensioners.

I believe I have the last non-hydraulic tensioners - 930.105.501.0R and collars. (Collars were installed right at top of tensioner piston so not sure what they would do..).

Am I right in assuming these are just spring force tensioners?

If so what is the side feature with the M5 bolt and brass washer for?

My issue is that I cannot depress the piston at all from the position shown - even if I put it against a wall and lean my 220lbs in behind it...

Is the spring THAT strong or do I have an issue. If the prior how the hell do you install?

Thanks again all,
Sam

[Flat6pac]

The tensioner is a hydraulic unit.
Put the tensioner in place close to the idler.
Take a long and hefty screwdriver and place it between the running idler area and the top of the piston, pressing down slowly collapsing the tensioner.
Tap the tensioner in place while holding the screwdriver level until the tensioner is seated.
Bruce

[Sam1905]

Bruce - thanks for the help.
I am thinking something must be wrong with them. I am using an 18" screwdriver and whether I lever against the idler, or even the inside top of the cam box I cannot get any movement at all with either unit.
It just doesn't seem I should have to put this much force on them...

[Sam1905]

Looking at the two units it seems there is something differing...??



May look into a rebuild kit...

[itsme]

Do you have a vise? You could stick it in and try to collapse it and see if it is locked up. Probably best to put something between each end and the vise jaws to keep from marring the end and shaft.

[Flat6pac]

I wouldnt touch the cam box to pry against, I ve done the install many times using the described method.
It doesnt collapse in the second or easily but keep pressure on the screwdriver.
Bruce

[Walt Fricke]

You are lucky - when I tried to pry against the cam box (chain housing), I cracked the box. Had to have it welded. Don't do that.

But the vise suggestion is what I thought too.

These are both spring and hydraulic functioning units. The spring is pretty strong, and it is all that puts pressure against the idler wheel assembly. The oil in the unit adds extra resistance against compressing the spring. And when the rod part is able to move out, the oil fills in behind it.

So it should be hard to depress the rod, as it is not just the spring you are pressing against. But the vice will do things, and should tell you if there is a mechanical obstruction inside (seems unlikely, but maybe) or not.

Do a search on chain tensioner function and you'll find exploded diagrams of the unit, which will tell you what the bolt is for - I think it is a lock holding some of the innards in place, but may be wrong.

The collar is a fail safe. You install the tensioner, and then the collar, and you lock the collar one eighth of an inch above the unit. That way, if the oil gets out or its seal fails, the whipping around the chain wants to do will not be able to depress the rod more than that 1/8". That may make a bit more noise than usual, but no chance of the chain skipping a tooth at either end sprocket.

It is widely believed that this "turbo" style tensioner, with the wide bushed idler levers/carriers, and a safety collar is adequate for all purposes, including especially race motors.

The later Carrera hydraulic tensioners are sometimes thought to be a solution applied after an earlier solution had fixed the problem. The oil pressure fed to these later tensioners is not actually pressure which pushes the rod part up. Rather, it just insures that the chamber below the rod is always kept full of oil. Oil enters the chamber under the rod part through a one way valve. When the chain compresses the rod some, oil slowly oozes out the top of the rod through a passageway. More than you wanted to know, since what you have should be fine if it is in good shape.

[Sam1905]

All - thanks for all the help. Latest below.

I did get one of the tensioners compressed in the vice and got it installed.
As you will see from the picture with my new chain the amount of compression required was significant. Because of this I was not comfortable with the lever approach - the angle of the screw driver was 45Deg and put as much side load on the arm and piston as vertical load. Things just looked bad... (See image.)





To get around this I compressed the tensioner in a vice across the mounting boss at the bottom and piston (Indicated). I then tightened a hose clamp as I depressed to keep it depressed (Clamping across the boss and not base ensures the hose clamp can move and take up the slack). I then dropped the tensioner straight in and removed the clamp with needle nose pliers. (ensure clamp adjuster is on front or it will stop you putting the tensioner in..)

I tried this with the second unit but it finally gushed oil everywhere....I guess it needs a rebuild..

[tharbert]

I'm not a big fan of those collars. When I diagnosed my failed tensioners and pulled the covers off, I saw that the PO had installed those exact same blue anodized collars but there was only one. After a bit of fishing, I pulled the missing collar, broken into 3 pieces, out of the sump. There is a thread somewhere here where someone disassembled the tensioner and placed washers inside, effectively limiting the travel of the tensioner the same as a collar but the washers remain safely tucked inside the tensioner. My search foo is weak. Maybe someone can find it...

[cmcfaul]

I belive there is a gernade pin that is used (or nail). You slowly compress the tensioner in a vise. Once completly compressed you insert the pin which holds it in place. Install the tensioner then pull the pin, expanding the shaft to spec.

Chris

73 911 E

[Sam1905]

I think that is just with the later Carrera tensioners..
May be wrong though...

[tharbert]

Ah, I found it... It's called the Jerry Wood modification?

Others simply put in washers.

To further promote my campaign against those collars, while I was looking for the link above, one thread mentioned those collars are not for hydraulic tensioners, only mechanical ones. You may want to check...or just toss the damn things away.

[cmcfaul]

I saw the not for hydraulic tensions mention and wondered why.

Chris

[Sam1905]

Different design...

[304065]

Sam the pin fits across the top of the tensioner and holds the piston down. When fitted the pin is perpendicular to the axis of the tensioner piston.

[DSPTurtle]

The art of this install required that you slip the tensioner on as lightly as possible before levering your screwdriver in there. 1/4 of an inch can make a simple task almost impossible. Rubber mallet, big screwdriver, lots of patience = win!

[Walt Fricke]

Guys - the collars are for both types of tensioner - the hydraulic and the pressure fed. The one kind of tensioner these are NOT for is the mechanical. You don't want to use mechanical tensioners for any purpose other than setting cam timing. Or maybe if you are very old school with a full race motor.

I believe the Jerry Woods system is only for the pressure fed tensioners, and won't work with these older style tensioners. Their internal construction is very very different.

The hose clamp is clever. There is a C shaped tool you can purchase. The idea is that you compress the tensioner in a vice, and slip the tool over both ends of the tensioner. This is tricky, because this means you are trying to have the vice press on only half of the narrow rod part, and I was never able to make it work. Then, when you have the tensioner installed, you pop this off. However, the tool didn't cost much. I'll keep the hose clamp in mind.

The pressure feds are much much easier to work with in this regard. A prudent guy keeps the pins which come with them (if new) for reuse next time the motor is apart. But a suitable nail works about as well.

[tharbert]

Oops, terminology got me... I did not mean mechanical, i.e. solid tensioners but rather non-pressure fed. (My pins hang on the peg board in my shop.)