E46 M3 Service Query - Valve Clearances
Discussion
Hi Chaps,
I have owned a 2002 E46 M3 Coupe for 2 years. It has covered 76,000 trouble free miles. Full BMW Service History to date.
The car is now due an Inspection 1 service, having covered 12,000 miles since last service Feb 2008.
I have heard mixed reports on the need for checking Valve Clearances. Obviously the franchised dealers are happy to take the rocker off at a cost of £700+.
Other garages I have spoken to adopt the "if it ain;t broke, don't fix it" approach to valve clearance checks.
I would be most grateful if you could provide any guidance / thoughts regarding the above.
Many thanks,
John
I have owned a 2002 E46 M3 Coupe for 2 years. It has covered 76,000 trouble free miles. Full BMW Service History to date.
The car is now due an Inspection 1 service, having covered 12,000 miles since last service Feb 2008.
I have heard mixed reports on the need for checking Valve Clearances. Obviously the franchised dealers are happy to take the rocker off at a cost of £700+.
Other garages I have spoken to adopt the "if it ain;t broke, don't fix it" approach to valve clearance checks.
I would be most grateful if you could provide any guidance / thoughts regarding the above.
Many thanks,
John
Great Pretender said:
Vroom2 said:
Hi Chaps,
Other garages I have spoken to adopt the "if it ain;t broke, don't fix it" approach to valve clearance checks.
And it is they whom you must avoid like the plague Other garages I have spoken to adopt the "if it ain;t broke, don't fix it" approach to valve clearance checks.
Do they need doing at the insp I on the E46?
I think they're insp II on my old E34, but that only goes 8-9k miles between indicated services.
Whatever, they are NOT an omit item. A garage told me that about my car, and that they only check them when the cars have a problem. I haven't been back.
Had a discussion once with a respected Indy regarding costs for my next inspection service (S54 engined z3). Made a point of telling me that it didn't include valve clearances and that that would cost extra (iirc he was in dispute with another customer who hadn't appreciated this). My understanding is it needs to be done and the car will need to be with the mechanic the night before so be ready to query whether the valve clearance is to be done if this isn't the suggested schedule.
Unique valve mechanism. All current BMW double-overhead-camshaft (DOHC) engines employ "bucket-type" hydraulic lifters, actuating the valves directly with minimum noise and no periodic adjustment. For the S54’s rpm potential, BMW M needed a valve train with less reciprocating mass.
To achieve this, they created a different actuating mechanism, using finger-type rocker arms. Pivoting on their own shafts (one on the intake side, one on the exhaust), these small – one could almost say dainty– arms reach out to provide the actuating surface between camshaft and valve. As the entire arm does not move the distance of valve lift, its effective reciprocating mass is less than its actual mass – and it weighs less than the "bucket tappets" in the first place. When all is said and done, the effective mass is 30%less; in turn, this allows lighter valve springs, which also reduce inertia. The lower valve train inertia helps the engine attain its 8000-rpmcapability.
As the system involves no hydraulic maintenance of valve clearance, it does have to be inspected periodically. Lead engine engineer Helmut Himmel asserts that it is unlikely that clearance will actually require adjustment, but if so it is done with shims (tiny metal discs of various thickness) without removal of the camshafts.
The rocker-arm arrangement also results in less friction. Unlike the rocker arms of BMW’s V-12 engine, however, these do not incorporate rollers, which would add too much mass for such a high-revving engine.
To achieve this, they created a different actuating mechanism, using finger-type rocker arms. Pivoting on their own shafts (one on the intake side, one on the exhaust), these small – one could almost say dainty– arms reach out to provide the actuating surface between camshaft and valve. As the entire arm does not move the distance of valve lift, its effective reciprocating mass is less than its actual mass – and it weighs less than the "bucket tappets" in the first place. When all is said and done, the effective mass is 30%less; in turn, this allows lighter valve springs, which also reduce inertia. The lower valve train inertia helps the engine attain its 8000-rpmcapability.
As the system involves no hydraulic maintenance of valve clearance, it does have to be inspected periodically. Lead engine engineer Helmut Himmel asserts that it is unlikely that clearance will actually require adjustment, but if so it is done with shims (tiny metal discs of various thickness) without removal of the camshafts.
The rocker-arm arrangement also results in less friction. Unlike the rocker arms of BMW’s V-12 engine, however, these do not incorporate rollers, which would add too much mass for such a high-revving engine.
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