Usage:
D399 (91B) Marine Engines, G399 (49C) Industrial Engine
- SUPPLEMENT: 04/06/92
SERVICE MAGAZINE; October 7, 1985; Page 3; "New Water Cooled Exhaust Manifolds Available; Existing Water Cooled Exhaust Manifolds Can Be Strengthened Or Salvaged" for D399 (91B) Marine Engines, G399 (49C) Industrial Engine.
The weld instructions on Illustration 3 are not correct. The correct Illustration 3 follows:
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Description of Change: New water cooled exhaust manifolds are available for D399 Marine Engines and G399 Industrial Engines. The new exhaust manifolds are stronger and more resistant to cracking than the former exhaust manifolds.
Former exhaust manifolds can be salvaged or strengthened by rewelding and adding a plate and gussets. The plate and gussets reduce flexing which can cause cracks to develop and allow the manifolds to leak.
Adaptable To: The new water cooled exhaust manifolds are direct replacements for the former water cooled exhaust manifolds. See the chart and the note.
NOTE: When installing a new or a reworked water cooled exhaust manifold it may be necessary to grind part of the flashing off the cylinder head between the exhaust ports. This will only be necessary on some engines.
Former 3N5805 and 3N5806 Water Cooled Exhaust Manifolds can be salvaged or strengthened by rewelding old welds and adding one 7W9157 Plate and 14-7W9158 Gussets to each manifold. The procedure to reweld and add the plate and gussets to the manifolds is as follows.
1. Remove the weld from the top and 25 mm (1.0") around the corners of each exhaust mounting flange. Use an air carbon arc torch or similar tool to remove the weld. See Illustration 1.
2. Reweld the exhaust mounting flanges. Stress relieve all welds as they are completed by striking them with a large hammer.
Illustration 1. Reweld exhaust mounting flanges.
3. Remove the material around any cracks or leak sources and reweld them. Stress relieve the welds.
4. Mark the location of the 14-7W9158 Gussets on the manifold. See Illustration 2.
Illustration 2. Location of 7W9158 Gussets.
5. Make sure the manifold is clean and free of weld splatter where the gussets are to be welded on. Weld the 14 gussets in position on the manifold as shown in Illustration 3. Weld the gussets on one side only.
Illustration 3. Weld 14-7W9158 Gussets to the manifold.
6. Clean and mark the areas of the 7W9157 Plates that are to be welded. See Illustration 4.
7. Clean the manifold and put the 7W9157 Plate in position on it. Position the plate so its ends are in alignment with the centerlines of the bolt holes in the exhaust mounting flanges. Also, put the bend in the plate even with the bend in the exhaust manifold. See Illustration 4.
8. When the plate is in the correct location, make a weld at the middle of the top side and at each end of the plate to hold it in position. Complete only the welds on the top side of the plate. Stagger the welds to reduce heat build-up and warpage. Stress relieve the welds.
Illustration 4. Locate and weld 7W9157 Plate to manifold.
9. Start at one end of the manifold and plate. Clamp the first two legs of the plate to the manifold as shown in Illustration 5.
10. Weld only the two bottom corners of the first (end) leg to the manifold. Remove the clamp from the first leg and clamp the third leg to the manifold. Leave the clamp on the second leg.
11. Weld the rest of the legs of the plate to the manifold the same way. Always keep a clamp on the leg that is being welded and on the next leg to be welded. Weld only the bottom corners of the legs at this time.
12. After all of the plate legs are welded at the corners on the bottom edge, complete the rest of the welds. Be sure to stagger the welds to reduce heat build-up and warpage. Stress relieve all of the welds as they are completed.
13. Grind all of the welds around the 7W9157 Plate so that they are even with it.
14. Connect an air pressure gauge with a shutoff valve to the manifold. Fill the manifold with water. Plug all water openings so the manifold can be checked for leaks.
15. Apply 280 kPa (40 psi) air pressure to the manifold and close the shutoff valve. Check for leaks or an air pressure drop. Repair the manifold if necessary.
16. Check the exhaust mounting flanges for flatness with a straight edge. To check for flatness, lay a straight edge across the first three consecutive exhaust mounting flanges and check the size of the gap. Move up one flange and check the size of the gap again. Repeat this process until all sets of three consecutive exhaust mounting flanges have been checked. The maximum amount that any three consecutive flanges can be out of flat is .254 mm (.0100"). If any flanges are more than .254 mm (.0100") out of flat, reface the flanges and check for flatness again.
Illustration 5. Location of clamps to weld first leg of plate to manifold.