In the article, we will consider how to disassemble the cylinder head, grind the valves and assemble the head

Preparing the car for the task

Remove the cylinder head as described in the article "How to replace Mazda 6 cylinder head and cover gasket"

Remove the intake manifold, as indicated in the previous article

Remove the exhaust manifold

Unscrew the spark plugs

Cleaning the combustion chambers from soot

Cylinder head: A - with variable valve timing 2.0 and 2.5 l; 1 - electromagnetic valve of the phase regulator; 2, 5 - camshaft bearing caps; 3 - mechanism for adjusting the position of the intake camshaft; 4, 7 - camshafts; 6 - camshaft sprockets; 8 - bolts; 9 - pusher; 10 - a bolt of fastening of a head of cylinders; 11 - cylinder head; 12 - gasket; 13 - cylinder block

Inspecting the head of the block

If the cylinder head has cracks or traces of burnout in the combustion chambers, replace the head

Removing burrs and nicks on the surface of the block head

Repair of Mazda 6 cylinder head

Checking the flatness of the surface adjacent to the cylinder block

We put a metal ruler with an edge on the surface of the head, first in the middle along, and then diagonally and measure the gap between the surface of the head and the ruler with a probe

The head must be replaced if the gap exceeds 0.025 mm

Repair of Mazda 6 cylinder head

Remove the camshafts

Pushers are more convenient to remove with a magnet or suction cup

Pushers cannot be interchanged, so we mark them

Store the tappets in the position in which they are installed on the cylinder head so that oil does not leak out of them

We clean the surfaces of the flanges of the head for installing manifolds from the remnants of gaskets and carbon deposits

Check for deformations for the intake and exhaust manifolds, replace the deformed head

We repair damaged threaded holes by threading with taps or installing a repair sleeve

Check the tightness of the cooling jacket plugs. When their fit is weakened, we restore it by chasing

To check the tightness of the block head, plug the hole in the head under the thermostat socket.

This can be done, for example, by installing a blank gasket made of thick cardboard under the thermostat housing and tightening the bolts of its fastening.

Pour kerosene into the channels of the water jacket.

If the level of kerosene decreases after 15-20 minutes, it means that there are cracks in the head and it must be replaced.

After checking, do not forget to remove the cardboard spacer.

Check the condition of the bearing surfaces under the camshaft journals in the head of the block.

If at least one of them shows signs of wear, scuffing or deep risks, grind the bearing beds and measure the gap between the beds and the camshaft journals after grinding.

If the gap is greater than the nominal, replace the block head.

To check the tightness of the valves, pour kerosene into the inlet and outlet channels of the head.

If within 3 minutes kerosene does not seep from the channels into the combustion chambers, then the valves are tight. Otherwise, lap or replace the valves.

Place a suitable stop under the valve to be removed (for example, a socket from the tool kit)

Repair of Mazda 6 cylinder head

We install a device for compressing valve springs on the head of the block

Compress the valve springs with the tool and remove the valve cotters

Then, gradually loosening the pressure on the device handle, we completely release the valve spring

Remove the fixture from the head of the block

Prying with a screwdriver, take out the valve spring plate and take out the spring

Car Cylinder Head Repair Mazda 6

Remove the valve from the block head

In the same way, we take out the remaining valves and remove the valve stem seals

Repair of Mazda 6 cylinder head

Removing carbon from the valves and inspecting them

Deformation of the valve stem and cracks on its plate are not allowed. If there is damage, replace the valve

Repair of Mazda 6 cylinder head

Check if the working bevel is too worn or damaged

Grinding of the working chamfer of valves is allowed

Minor scratches and scratches on the chamfer can be removed by lapping the valve against the seat

Do not clean the valve stems with wire brushes and scrapers, so that there are no marks on the stems

Check the concentricity of the valve disc and the seat: apply a thin layer of graphite (pencil lead) to the chamfer of the valve head, insert the valve into the guide sleeve and, slightly pressing against the seat, turn

Repair of Mazda 6 cylinder head

Traces of graphite on the chamfer of the seat indicate the concentricity of the valve and seat

Valve wear zones: 1 - the zone of the least rod wear; 2 - end of the rod; 3 - groove for crackers; 4 - zone of the least wear of the rod; 5 - working chamfer; 6 - plate edge

Check the wear of the valve stem in the places shown in the figure

Nominal valve sizes:

  • Diameter of inlet valve head 35.95 mm;
  • Exhaust valve head diameter 31.45 mm;
  • Inlet valve stem diameter 6.980 mm;
  • Exhaust valve stem diameter 6.956mm;
  • Intake and exhaust valve height 89.95mm;
  • The angle of the working chamfer of the intake and exhaust valves is 45º.

Check the condition of the grooves 3 of the valve stem for crackers.

If traces of chipping of the edges of the grooves and wear of the cylindrical part are found, replace the valve

Check the condition of the valve guides by measuring the inner diameter of the hole. The gap should not exceed 0.1 mm

Check the condition of the valve seats. The seat bevels must be free of wear, pitting, corrosion, etc.

Valve seats can be replaced at a specialist workshop.

Minor damage (small marks, scratches, etc.) can be removed by lapping the valves

More significant defects in valve seats are eliminated by grinding, maintaining for engine valve seats, dimensions 45 ° with a belt width after grinding for all valve seats 1.56 mm

It is recommended that saddles be ground in a specialized workshop, as this requires special tools and equipment.

If grinding fails, replace the valve seats.

Replace the valve stem seals regardless of their condition.

Inspect the valve springs. Cracks and reduction of elasticity of springs are not allowed.

If possible, determine the elasticity of the springs by the force developed.

Replace warped springs (deformation in the free state more than 1.6 mm) and springs with cracks.

Always replace the gaskets of the intake pipe, exhaust manifold and cylinder head with new ones, since the gaskets removed, even outwardly not damaged, may be heavily compressed and will not ensure tightness of the seals