Because hydraulic tensioners keep the chains constantly taut, regardless of chain stretch or shoe wear, there is no need to adjust the chain tension during operation

Hydraulic chain tensioner

Plunger 4 is installed in housing 5. Spring 6 is inserted into the plunger, which is compressed by a threaded plug 1. Check ball valve 2 is installed in plug 1. Locking ring 3 and retaining ring 7 are put on plunger 4.

In the figure, the tensioner is shown in a non-working "charged" state, when the retaining ring 7 keeps the plunger 4 from moving.

To bring the tensioner into working condition, to "discharge" it, you need to press the end of the plunger so that the retaining ring 7 moves into the groove of a smaller diameter on the plunger, and under the action of the spring 6 the plunger moves out of the housing 5.

The hydraulic tensioner is installed on the engine in a charged state.

Plunger 4, under the action of spring 6 and oil flowing through valve 2 from the engine lubrication system, presses on the tensioner shoe and keeps the chain taut.

As the chain stretches and the tensioner shoe wears out, the plunger 4 moves further out of the body 5, while the locking ring 3 moves into the next annular groove on the body, preventing the plunger from moving in the opposite direction.

When the chain hits the tensioner shoe, for example, when the engine operation mode changes, the plunger 4 moves back into the housing 5 by the width of the groove for the locking ring 3.

At the same time, it compresses spring 6. In addition, valve 2 closes and additional damping occurs due to the fact that oil is squeezed out through the gap between the plunger and the body.

The hydraulic tensioners of the upper and lower chains are exactly the same.

Removal and disassembly

ZMZ camshaft drive chain hydraulic tensioner

Removing and installing hydraulic chain tensioners

Remove the screws 1 while holding the cover 2, as the spring force acts on it.

Then, carefully remove cover 2 with the cover gasket and the noise-insulating gasket of the hydraulic tensioner.

Remove the hydraulic tensioner from the channel in the block head.

ZMZ camshaft drive chain hydraulic tensioner

Remove screw plug 1.

The hydraulic tensioner must not be clamped in a vice, so you need to clamp the key in a vice and insert the hydraulic tensioner into it.

Remove plug 1 and take out spring 2.

ZMZ engine camshaft drive chain hydraulic tensioner

Remove plunger 1 from hydraulic tensioner body 2

Inspection

It is forbidden to dismantle the plunger and the hydraulic tensioner housing.

1. After disassembly, wash all parts in gasoline and dry.

Inspect the plunger, if there are scratches or nicks on its surface, the locking or retaining ring is broken, the hydraulic tensioner needs to be replaced.

2. Examine the hull. If there are scuffs, deep scratches on the inner surface of the housing, or the annular grooves for the locking ring are damaged, replace the hydraulic tensioner.

3. The plunger in the housing must move freely. If the plunger in any position “sticks” in the body, the hydraulic tensioner is replaced.

4. The plunger must move in the body when the stop ring has entered the annular grooves on the body, only in the direction in which it moves under the action of the spring.

If the plunger moves in the opposite direction, replace the hydraulic tensioner.

Build and install

Before assembling, lubricate the plunger and the inner surface of the housing with engine oil. To assemble the hydraulic tensioner, it is recommended to make a mandrel, the dimensions of which are shown in the figure: "Charging" the hydraulic tensioner using the ring.

1. Clamp the mandrel vertically in a vise.

ZMZ engine camshaft drive hydraulic tensioner

2. Install the hydraulic tensioner housing on the mandrel.

3. Insert the plunger into the body until the locking ring of the plunger stops against the mandrel.

4. standing up Insert a spring into the plunger and fill the tensioner with engine oil. While compressing the spring, tighten the screw plug. In this case, the locking ring of the plunger must enter the groove on the body and keep the plunger from moving, i.e. the tensioner will be charged.

5. Remove the hydraulic tensioner from the mandrel. Do not press the plunger, as this will cause the plunger lock ring to come out of the groove on the body and the plunger will come out of the body, i.e. the hydraulic tensioner will be discharged.

ZMZ engine camshaft drive chain hydraulic tensioner

6. If there is no mandrel for assembling the hydraulic tensioner or it is not possible to make it, you can assemble the tensioner as follows: bend the ring from a strip of metal 1.0 mm thick and about 15 mm high.

For this, you can use a piece of tape from an old band clamp; insert the plunger into the body of the hydraulic tensioner so that the retaining ring on the plunger is opposite the groove in the body; put the bent ring on the table.

Install the body with the plunger on it so that the ring fits between the body and the plunger until it stops in the retaining ring; insert a screwdriver into the plunger and with a light hammer blow on the screwdriver move the plunger down.

In this case, the retaining ring will move to a larger diameter of the groove on the plunger and enter the groove on the body, holding the plunger in a charged state; insert the spring into the plunger.

Fill the tensioner with engine oil and tighten the plug against the spring force; take out the made ring.

Do not press the plunger, so as not to discharge the hydraulic tensioner.

7. Lubricate the channel for the hydraulic tensioner in the head of the block with engine oil and install the hydraulic tensioner there until it stops against the tensioner shoe.

Do not press the hydraulic tensioner so as not to discharge it.

8. Install the rubber noise-insulating gasket in the cover 2. Install cover 2 with gasket on the block head, tighten bolts 1.

Unscrew plug 3 and press the hydraulic tensioner with a suitable rod through the hole under the plug, moving it to the stop, and then release it.

The hydraulic tensioner will be discharged, its body will rest against cover 2 under the action of the spring, and the chain will be tensioned. Screw plug 3 into cap 2.

9. In the same way, remove and install the hydraulic tensioner of the lower chain.

If there is no mandrel for assembling the hydraulic tensioner or it is not possible to manufacture it, you can assemble the tensioner as follows:

Removing and installing hydraulic chain tensioners

We reduce the vise jaws, leaving a gap of 19 mm between them.

Do not vise the tensioner housing. When disassembling two hydraulic tensioners at once, do not confuse their plunger pairs, as they are matched with a certain clearance.

Removing and installing hydraulic chain tensioners

Removing and installing hydraulic chain tensioners

Having installed the tensioner body in a vise, as in the mouth of a key, we unscrew the valve with a wide-blade screwdriver.

Removing and installing hydraulic chain tensioners

Removing and installing hydraulic chain tensioners

Remove the spring from the body

Remove the plunger.

We wash all parts in gasoline or kerosene, blow with compressed air and lubricate with engine oil.

Removing and installing hydraulic chain tensioners

From a steel sheet with a thickness of 0.8-1.0 mm, cut out a strip (10-15 mm wide and 25 mm long).

With round-nose pliers or on a mandrel, bend it into a ring with a diameter like that of a plunger.

Removing and installing hydraulic chain tensioners

Removing and installing hydraulic chain tensioners

With a manufactured mandrel, we press the spring in the hydraulic tensioner body.

Installing the plunger into the body.

Removing and installing hydraulic chain tensioners

Removing and installing hydraulic chain tensioners

If necessary, use a thin screwdriver to guide the locking ring

Use a screwdriver to press the bottom of the plunger all the way.

Removing and installing hydraulic chain tensioners

Removing and installing hydraulic chain tensioners

We install the spring into the plunger, and the body itself into a vise.

Overcoming the resistance of the spring, we wrap the valve into the hydraulic tensioner body.

Removing and installing hydraulic chain tensioners

Removing and installing hydraulic chain tensioners

For a properly charged tensioner, the plunger must be fully inserted into the body

Use a screwdriver to tighten the valve, holding the body in a vise (as in disassembly).

Do not press on the protruding end of the plunger, and after installation in the channel of the head of the block - on the tensioner itself

Discharging the hydraulic tensioner

After installing the hydraulic tensioner on the engine, it must be brought into working condition - discharged. To do this, use a 12 key to unscrew the plug from the hydraulic tensioner cover.

Removing and installing hydraulic chain tensioners

Removing and installing hydraulic chain tensioners

Using a screwdriver through the hole, press the tensioner, which, “discharged”, will push it out.

Removing and installing hydraulic chain tensioners

Install the cork in place.

Removing and installing hydraulic chain tensioners

This is what an “undischarged” hydraulic tensioner looks like.

Removing and installing hydraulic chain tensioners

...and so - "discharged".