Engine roars (and vibrates)
Thread Starter
Instructor
Joined: Jun 2009
Posts: 107
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From: NOVA
Engine roars (and vibrates)
So, my car (and my credit rating) recently went through new clutch surgery and major service. all went well. However, I have noticed a peculiar problem. Under load (3500+ RPM) and with the a/c engaged a loud "roaring" emanates from the rear and a vibration travels to the gear shift.
When I disengage the a/c the gentle tapping of the valves returns.
I have been able to repeat these symptoms several times, turning the a/c off and on. The a/c works normally. It is impossible to know if this existed prior to the engine drop as I hadn't used the a/c all winter.
I am guessing this is either motor mounts or a bad belt. Any opinions out there?
If it is the motor mounts can anyone offer the definitive replacement? The car is not tracked. I am unclear which of the Wevos are best for daily driver use. I understand this is a relatively simple DIY project.
Thanks!
When I disengage the a/c the gentle tapping of the valves returns.
I have been able to repeat these symptoms several times, turning the a/c off and on. The a/c works normally. It is impossible to know if this existed prior to the engine drop as I hadn't used the a/c all winter.
I am guessing this is either motor mounts or a bad belt. Any opinions out there?
If it is the motor mounts can anyone offer the definitive replacement? The car is not tracked. I am unclear which of the Wevos are best for daily driver use. I understand this is a relatively simple DIY project.
Thanks!
Rennlist Member
Joined: Dec 2003
Posts: 7,211
Likes: 490
From: NC
...with the a/c engaged a loud "roaring" emanates from the rear and a vibration travels to the gear shift.
When I disengage the a/c the gentle tapping of the valves returns.
I have been able to repeat these symptoms several times, turning the a/c off and on. The a/c works normally. It is impossible to know if this existed prior to the engine drop as I hadn't used the a/c all winter
When I disengage the a/c the gentle tapping of the valves returns.
I have been able to repeat these symptoms several times, turning the a/c off and on. The a/c works normally. It is impossible to know if this existed prior to the engine drop as I hadn't used the a/c all winter
I experienced the same thing after I converted my AC to 134. I hadn't used my AC in months, but when I turned it on I heard the same "roaring" noise you mention.
I couldn't figure it out until a couple months later a forum member (John Boggiano) mentioned something about the AC lines running across the engine. I opened the lid and saw that the AC lines had a pressed marks on it from where it came in contact with the engine lid. I also put a piece of paper down on the engine to see where the contact was coming from. (see pics)
I had also changed the motor mounts over the winter too (which raised the engine about an inch).
Last edited by 911Jetta; May 3, 2011 at 03:18 PM.
Rennlist Member
Joined: Dec 2003
Posts: 7,211
Likes: 490
From: NC
I still hear it, but it's not as loud since I've moved the little rubber holders on the refrigerant line. Since they wrap around the refrigerant lines, they protrude a little higher in the engine bay. It's hard to find a spot where they don't come in to close contact with the lid.
Your A/C clutch might be going bad also, but try engaging/disengaging the A/C with the lid down, then try it again with the lid up? I get my car back from the shop tonight (hopefully!) and I'll try it with the engine lid open/closed also.
Your A/C clutch might be going bad also, but try engaging/disengaging the A/C with the lid down, then try it again with the lid up? I get my car back from the shop tonight (hopefully!) and I'll try it with the engine lid open/closed also.
Thread Starter
Instructor
Joined: Jun 2009
Posts: 107
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From: NOVA
Me and a guy at work spent some time examining the problem. The deck lid was not vibrating so I don't believe it is related to the lines rubbing.
We also reviewed the workings of the compressor clutch. It seemed to work smoothly, clicking on and off. Under power it did not wobble or act as if there was a bad bearing or anything.
But, the vibration came up through the shifter and things did get loud (the "roar").
So...I don't think the A/C is the culprit other than adding to the load at higher rpm. The wrench has suggested a bad belt or adjustment. My money is on the motor mounts.
We also reviewed the workings of the compressor clutch. It seemed to work smoothly, clicking on and off. Under power it did not wobble or act as if there was a bad bearing or anything.
But, the vibration came up through the shifter and things did get loud (the "roar").
So...I don't think the A/C is the culprit other than adding to the load at higher rpm. The wrench has suggested a bad belt or adjustment. My money is on the motor mounts.
