D7 Cylinder Head Repair Experience
This last spring my BMW-D7 in my S2 7.9 would not start after the winter layover. Even after repeated efforts of cranking for a full minute with rest periods in between, it would not start. The cold starting techniques in the manual no longer worked either. The engine had become progressively harder to start all the previous summer. The public library had many books on repair of diesel engines (big and small) which I had read over the winter. Didn’t qualify me as a diesel mechanic, but gave me a much clearer idea how they worked and what may have been the trouble. Tried a new injector thinking that the old one had been overheated because of having lost the water pump the previous summer. No fire, only gray-white smoke was emitted from the exhaust. A diesel technician informed me that gray or white smoke was consistent with loss of compression. The owner’s manual says compression ratio is 22:1, but this is of little value without knowing the volumes of the combustion chamber and the test gage. With little to lose, I removed the head and found evidence of leakage across the head gasket. Not wanting to disconnect electrical, fuel, and water lines, I chose to remove the head and cylinder without removing the engine from the boat. It’s a tight fit, but by lowering the engine mounts nearly all the way, there was clearance. However perhaps a few unkind words concerning the builders were said in the process. One does need to improvise a little to apply torque to fasteners that can be felt but not seen.
On a suggestion from this forum, I contacted Hatz Diesel in Waukesha WI. They informed me that BMW and Hatz had made the D7 and D12 in a joint venture. The Hatz version of the D7 was an HE 673. They sent a parts list. However they said parts had to come through the local distributors which for me was Great Northern Equipment in Rogers MN. They in turn sent me to a local repair shop that didn’t stock them. It was much easier getting the required parts from V12 Engineering. V12 was very prompt, helpful in finding the correct parts, and lent a little free advice. I would do business with them again. V12 has a complete BMW parts list which helps in locating and ordering the correct part and provides a detailed exploded view which helps in assembly.
Jack’s Small Engines in Rogers MN repairs Hatz diesels. Took the head there to have the valves lapped and the cylinder honed. He was very deliberate in checking out the specifications for extraction height etc. because tolerances are closer in a diesel. He found that the exhaust valve seat was pitted. This was probably the main problem all along. So another shop bored out the seat and installed an insert. I then somehow managed to re-install everything (apparently) correctly, and the D7 fired up easily and has run great all this summer. I mean to tell you it runs sweet.
The total bill for the valve work, the new rings, the new seals, and shipping came to just under $350 and a couple trips to the confessional. (If I can be forgiven, I suppose so can the BMW designers)
don harasyn
Repair of a BMW-D7 cyclinder head
Moderators: Tim Bosma, Tom Elsen
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Ray Suarez
Do you have a parts list?
Thanks for your great post on the D7. I am having the same problems you described! I was contemplating a change to OB, but would prefer to keep my D7. Would you have:
o A list of parts you used,
o Special tools (if any),
o Time of project,
Any info would be greatly appreciated.
--ray
raymond.suarez@veritas.com
o A list of parts you used,
o Special tools (if any),
o Time of project,
Any info would be greatly appreciated.
--ray
raymond.suarez@veritas.com
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Don Harasyn
- Posts: 2
- Joined: Wed Sep 24, 2003 12:00 am
RE: Repair of D7
Ray,
If you decide to tackle this, buy the BMW parts list from V12 Engineering. The exploded views are excellent, helping both with correct assembly and determining which seals to replace. The parts I installed were as follows:
1125 1329 686 (1) D7, Ring set, std., 73.0 mm (74 mm is also alvailable)
1112 1329 528 (1) D7 Cylinder head o-ring
1111 1329 520 (2) D7 Cylinder head stud o-ring
1112 1329 530 (1) D7 Head gasket
1112 1329 531 (4) Head gasket o-rings
1711 1329 391 (1) D7/D12 thermostat 50deg C
1353 1329 667 (1) Fuel injector, hose bib style (banjo fitting style also available)
1162 1329 005AM (1) D12 Exhaust manifold gasket, Aftermarket (the OEM exhaust gasket caused extreeme acute sticker shock)
I should have ordered an extra copper shim or two (1111 1329 759), but I successfully field fabricated (not a recommended activity) one from SS shim stock. This shim effectively adjusts the clearance between the head and the piston at TDC.
For tools I mainly relied on the tool kit that came with the engine and my own metric sockets, open, box-end wrenches etc. I purchased no special tools and did not make any. Although in a couple places I had to be a little creative by setting a small wrench on a hard-to-reach fastener and then using a wrench to turn the wrench. Keep a pencil and paper handy to sketch how some of the assemblies go together. For example the compression piston rings have tapered IDs that face upward (presumably common knowledge to a mechanic, but new to me). I think the idea is for the force of compression and combustion to spread the ring against the cylinder wall. Turned out that a piston ring installation tool was unnecessary. Didn't have room for it anyway. I was able to compress the rings sufficiently by hand and slip the cylinder over. The cylinder has a tapered entry bore which greatly helps to lead the rings into the cylinder proper. You will want a micrometer and vernier calipers and be patient about making the measurements. Once the head is back on, check the clearance between valves and piston at TDC by mashing electrical solder (use a wire diameter close to the recommended clearance) and measuring it with the micrometer. I had to disassemble and add the shim.
I spent a few weeks reading about diesels before starting this project. The total elapsed time of the project was 8-9 weeks. I'm guessing it was 25-50 hours of my time (wrenching, measuring, wondering, ordering, drinking). I never wanted to start the project, but felt the situation demanded I give it a try because there was no one to take it on at a reasonable price and schedule. It helped that the engine had been progressively running poorly (especially in reverse) and finally just wouldn't start. There was nothing to lose. Glad I stayed with it and hope this helps.
don harasyn
If you decide to tackle this, buy the BMW parts list from V12 Engineering. The exploded views are excellent, helping both with correct assembly and determining which seals to replace. The parts I installed were as follows:
1125 1329 686 (1) D7, Ring set, std., 73.0 mm (74 mm is also alvailable)
1112 1329 528 (1) D7 Cylinder head o-ring
1111 1329 520 (2) D7 Cylinder head stud o-ring
1112 1329 530 (1) D7 Head gasket
1112 1329 531 (4) Head gasket o-rings
1711 1329 391 (1) D7/D12 thermostat 50deg C
1353 1329 667 (1) Fuel injector, hose bib style (banjo fitting style also available)
1162 1329 005AM (1) D12 Exhaust manifold gasket, Aftermarket (the OEM exhaust gasket caused extreeme acute sticker shock)
I should have ordered an extra copper shim or two (1111 1329 759), but I successfully field fabricated (not a recommended activity) one from SS shim stock. This shim effectively adjusts the clearance between the head and the piston at TDC.
For tools I mainly relied on the tool kit that came with the engine and my own metric sockets, open, box-end wrenches etc. I purchased no special tools and did not make any. Although in a couple places I had to be a little creative by setting a small wrench on a hard-to-reach fastener and then using a wrench to turn the wrench. Keep a pencil and paper handy to sketch how some of the assemblies go together. For example the compression piston rings have tapered IDs that face upward (presumably common knowledge to a mechanic, but new to me). I think the idea is for the force of compression and combustion to spread the ring against the cylinder wall. Turned out that a piston ring installation tool was unnecessary. Didn't have room for it anyway. I was able to compress the rings sufficiently by hand and slip the cylinder over. The cylinder has a tapered entry bore which greatly helps to lead the rings into the cylinder proper. You will want a micrometer and vernier calipers and be patient about making the measurements. Once the head is back on, check the clearance between valves and piston at TDC by mashing electrical solder (use a wire diameter close to the recommended clearance) and measuring it with the micrometer. I had to disassemble and add the shim.
I spent a few weeks reading about diesels before starting this project. The total elapsed time of the project was 8-9 weeks. I'm guessing it was 25-50 hours of my time (wrenching, measuring, wondering, ordering, drinking). I never wanted to start the project, but felt the situation demanded I give it a try because there was no one to take it on at a reasonable price and schedule. It helped that the engine had been progressively running poorly (especially in reverse) and finally just wouldn't start. There was nothing to lose. Glad I stayed with it and hope this helps.
don harasyn
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Doug
D7 Reverse
Don,
I am having trouble with my D7 backing up. The motor seems loaded very heavily. After reading your post I believe that possibly it is time for rings and a valve job. It runs very well going forward though. Any thoughts?
Doug Pope
I am having trouble with my D7 backing up. The motor seems loaded very heavily. After reading your post I believe that possibly it is time for rings and a valve job. It runs very well going forward though. Any thoughts?
Doug Pope
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Ray Suarez
Doug,
A 3 years ago my D7 started with the same problem that you described when backing up. The gear is taller in reverse, making a weak engine fail first in reverse. Also, tough to start in the cold.
2 years ago it became tough to start. After it was warm, forward was ok.
Last year it would only run if I revved the engine and threw the transmission into into forward. Near the end of the year it just would not start.
After contemplating an outboard, I had the head cleaned, valves replaced and exhaust ports scraped of crud. The mechanic described Don's post exactly.
After trailering it back from the mechanic, I was anxious to turn it over. It started it in the cold this winter at a 45 degrees. It never would have done that 3 years ago.
Total cost $350 parts and $500 in labor. That was $1,200 cheaper than a new OB (not including all the headaches of retrofitting).
A 3 years ago my D7 started with the same problem that you described when backing up. The gear is taller in reverse, making a weak engine fail first in reverse. Also, tough to start in the cold.
2 years ago it became tough to start. After it was warm, forward was ok.
Last year it would only run if I revved the engine and threw the transmission into into forward. Near the end of the year it just would not start.
After contemplating an outboard, I had the head cleaned, valves replaced and exhaust ports scraped of crud. The mechanic described Don's post exactly.
After trailering it back from the mechanic, I was anxious to turn it over. It started it in the cold this winter at a 45 degrees. It never would have done that 3 years ago.
Total cost $350 parts and $500 in labor. That was $1,200 cheaper than a new OB (not including all the headaches of retrofitting).