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Low compression

Tiny
KRHYNE
  • MEMBER
  • 2001 BMW X5
  • 3.0L
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 200,000 MILES
I have finally taken the head off I cleaned it up really good. It wasn’t warped but as I cleaned the engine I let the solution sit in the cylinders and I noticed the next day two of the cylinders the solution was gone. Is that a problem? And on the head three of the valve stems were in the open position while the rest were sealed is that a problem too if so what should be done?
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Wednesday, July 31st, 2019 AT 1:08 PM

10 Replies

Tiny
STEVE W.
  • MECHANIC
  • 13,573 POSTS
The cleaner will drain past the rings normally as they don't seal fully even in a new vehicle.
As for the valves, are the cams still installed? If so the open valves would be normal. If the cams are removed then open valves would be an issue.
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Wednesday, July 31st, 2019 AT 1:28 PM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
Hi Krhyne,

The fluid not staying in the cylinder is not necessarily an issue. Did you find that there was low compression on these cylinders? If so, then it is probably related to a ring issue. However, if you don't have low compression on these cylinders then I wouldn't worry about it. Also, you need to change the oil if you still have the oil pan on it. Because if this drained out and did not evaporate then that is in the oil now.

As for the valves, if the camshaft is still installed then some of the valves will be open because of the lobes on the cam. So I would not be worried about this either.

Let me know if you have more questions. Thanks
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Wednesday, July 31st, 2019 AT 1:29 PM
Tiny
KRHYNE
  • MEMBER
  • 8 POSTS
Thanks for the information. I have low compression only in the number two cylinder at 45. Now should I continue with just the head gasket change or should I now worry about the piston ring? Also the number three cylinder was 210 but the rest were fine I mean between spec.
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Thursday, August 1st, 2019 AT 5:16 AM
Tiny
STEVE W.
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What did the old head gasket show? Any damage around that cylinder? If you rotate the cams do the open valves close while others open? What do the cylinder bores look like? Clean and smooth with no scoring or damage? If the problem was a blown head gasket then a new one should repair the problem. If it was due to a bad valve or broken piston rings then it won't. No easy way to test those with the engine apart.
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Thursday, August 1st, 2019 AT 2:33 PM
Tiny
KRHYNE
  • MEMBER
  • 8 POSTS
Yes, the gasket had this white residue by the number two cylinder and on the end was a patch of cruddy oil, but not broken or anything. As for the cams when I rotate them the valves open and close I didn’t see any scores or damage as I turned them with my wrench. If you are talking about the bottom of the valves some had this hard crud on them, but I cleaned most of it. I will start putting everything back if it doesn’t work should I junk it and look for a used engine or another car?
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Friday, August 2nd, 2019 AT 3:55 AM
Tiny
STEVE W.
  • MECHANIC
  • 13,573 POSTS
Okay, that could be the indication that the leak was in the gasket. If you get it together and still have no or low compression you can test it to see where it is leaking out by using a simple leak down tester. It is very possible that the valve deposits and the gasket combined to cause the problem. It doesn't take much of a leak to cause compression loss. Just be sure you time it correctly.
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Friday, August 2nd, 2019 AT 1:00 PM
Tiny
KRHYNE
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  • 8 POSTS
What is when your car is cold and you start it up and the temperature gauge goes right to red, but the car is not hot at all?
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Sunday, March 8th, 2020 AT 10:42 AM
Tiny
STEVE W.
  • MECHANIC
  • 13,573 POSTS
If this is on the car with low compression, check that the temperature sending unit didn't get damaged or a wire pinched when you were putting it back together.
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Sunday, March 8th, 2020 AT 3:45 PM
Tiny
KRHYNE
  • MEMBER
  • 8 POSTS
Hi, I have a 2012 Audi A7. I changed the water pump and thermostat and now I have these codes: p10a6 and p10a7. I could use some expert knowledge.
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Sunday, July 11th, 2021 AT 8:39 PM
Tiny
STEVE W.
  • MECHANIC
  • 13,573 POSTS
Welcome back. We have a policy to try to keep makes and models separate so that people searching the site don't get all mixed up. So could you please use this link and ask this as a new question. https://www.2carpros.com/questions/new
Thank you.
As I recall those codes are both related to the intake flap control circuit. As such I would check that the wiring is plugged in properly and the harness is okay.
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Sunday, July 11th, 2021 AT 8:49 PM

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