Engine body - Service procedures

3

Now close the cock (B). The manometer should not drop for two minutes if the pressure testing device is to be considered reliable.

Leakage test

1

10 ltr: Fit the clamp 6685 and the expander screws 2124 (2 pcs), see fig.

12 ltr: Fit connecting washer 6683 and the expander screws 2124 (2 pcs), see fig.

Do not tighten the wing nuts too hard to avoid damaging the rubber seal.

Submerge the cylinder head in water, temp. approx. 70°C (158°F)

4

Connect the test device to the compressed air supply and open the cock.

IMPORTANT! Follow the relevant safety instructions. Do not stand over the expander screws.

2

Check that the knob on the reducing valve is unscrewed and connect the hose from the pressure testing device to the cylinder head.

5

Pull out the circlip for the knob on the reducing valve. Increase the pressure by screwing in the knob until the the manometer shows 50 kPa (7.25 psi). Hold this pressure for one minute, then increase to 150 kPa (21.75 psi) . Lock the knob by pressing in the circlip and closing the cock. Check after 1–2 minutes if the pressure drops or if air bubbles escape from the water.

6

Release the compressed air hose. Open the cock and reducing valve. Remove the testing equipment.

Cracks in cylinder head

During the renovation of engines which have gone many hours an inspection of the cylinder head may reveal heat cracks between the valve recess and hole for the injector; see Fig. below.

The cylinder head does not need to be replaced or scrapped because of these heat cracks, if there is no leakage found during pressure testing. Heat cracks stop after a time and they have proved not to have any effect on engine performance. The cracks begin at the copper sleeve of the injector and run towards the recess for the valve seat.

Cylinder head, inspection

The cylinder head warp shall be max. 0.02 mm (0.0008"). If the warp is greater than 0.02 mm, or if there are blasting marks, the cylinder head shall be machined flat or replaced.

12 ltr engines: after grinding new sealing grooves must be milled.

The flame edge groove does not require machining as long as the grinding stays within the tolerance for min. cylinder head height; see Cylinder head, surface grinding below.

Cylinder head, surface grinding

Special tool: 2479, dial test indicator

1

Cracks can be caused by over-tightening the fixture for the injector. This type of crack has when tested not resulted in gas or coolant leakage, since the crack has not continued through the base of the cylinder head. Where leakage has been confirmed this has proved to be the result of impurities or damage to the seat of the copper sleeve, which must therefore be corrected.

Cylinder heads in Volvo Penta’s replacement system may also display heat cracks. These cracks are checked during reconditioning and are not considered to be of importance, that is, the cylinder heads are guaranteed to be fully usable.

Surface roughness shall after surface grinding be max. 1.6 RA. The distance (A) from the machined surface of the cylinder head to the valve disc must not be less than minimun value specified in Workshop Manual, Technical Data for each engine concerned. If additional grinding of the cylinder head is necessary the valve seats must be milled to size.