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2004 Z4 2.5 M54 Compression Test
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2004 Z4 2.5 M54 Compression Test
See attached the results of compression test on a 2004 BMW Z4, E85, with 2.5, M54 engine. 126,000 miles. The engine was dry and cold. The pictures are labeled with cylinder number. I thought I would post this. The compression test is a simple test and not too time consuming. Remove all the plugs and pull the fuel pump relay. I bought this car recently and wanted to check the compression before proceeding with other repairs.
Oh my the water pump, there is a support frame directly in front of the water pump, so you must loosen the left motor mount and slightly raise the engine to get the water pump out. Clearly an oversight, I think. At least it has an electric radiator fan, so there is nothing mounted to the front of the water pump. Cheers!
Oh my the water pump, there is a support frame directly in front of the water pump, so you must loosen the left motor mount and slightly raise the engine to get the water pump out. Clearly an oversight, I think. At least it has an electric radiator fan, so there is nothing mounted to the front of the water pump. Cheers!
Last edited by BMW Spartanburg SC on Sat Feb 17, 2024 9:27 pm, edited 1 time in total.
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2004 Z4 2.5 M54 Compression Test
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2004 Z4 2.5 M54 Compression Test
I always thought a compression test had to be performed on a hot engine
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2004 Z4 2.5 M54 Compression Test
Dear Mike6, my understanding is that a hot engine would potentially give the best readings since metal parts have expanded. If I wasn't satisfied with the 'cold' readings, I would proceed to check with hot engine, putting small amount of oil in cylinders, etc.
Dear j3nks79, since I recently bought this car, I was trying to test that the engine was 'healthy' and no low compression on any one cylinder. I didn't do a leak-down test since its more involved, need compressed air and some extra fittings...
Dear j3nks79, since I recently bought this car, I was trying to test that the engine was 'healthy' and no low compression on any one cylinder. I didn't do a leak-down test since its more involved, need compressed air and some extra fittings...
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2004 Z4 2.5 M54 Compression Test
I'm no expert but I always thought removing plugs from a hot engine isn't a good idea due to the potential of stripping the threads
04 2.2i Sapphire Black Roadster
- BumpyZ4
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2004 Z4 2.5 M54 Compression Test
Nope, the aluminum heads expand more than the steel spark plugs when hot so should come out easier.
2003 E85 3.0i Sterling Gray
KLR 650
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Diva Roadster (Kit Car)
- grannyknot
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2004 Z4 2.5 M54 Compression Test
Those numbers look pretty good for a cold engine, did you also remove the spark plugs and wire the throttle open? Doing that eliminates any resistance to the incoming and out going air and gives a more accurate reading.
A reading on a hot engine will give you the most accurate numbers of that engine but a cold reading should still show if the readings are consistent, yours are.
A wet test, squirt of oil in each cyl will just let you see how worn the rings are, a leakdown is done if you find a cyl with low numbers and want to pin point where the leakage is happening.
A reading on a hot engine will give you the most accurate numbers of that engine but a cold reading should still show if the readings are consistent, yours are.
A wet test, squirt of oil in each cyl will just let you see how worn the rings are, a leakdown is done if you find a cyl with low numbers and want to pin point where the leakage is happening.
2008 E86 M coupe
Toronto, Ontario
Toronto, Ontario
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2004 Z4 2.5 M54 Compression Test
Thanks you all,
I did remove the spark plugs but didn't wire the throttle open.
I did remove the spark plugs but didn't wire the throttle open.