Engine tapping when unloaded
#1
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Hi guys,
Let's see what the brain-trust has for this:
I have a distinct tapping coming from the engine only when it's not loaded. At idle, in Park or Neutral, it's tapping about 200 times a minute. Put it in gear (forward or reverse) and the tapping stops.
Same thing when I driving at a medium speed: If the engine's unloaded I can hear the tapping echo off a curb or wall. However, if add the slightest bit of throttle or take my foot off the gas (negatively loading the engine) the tapping disappears.
I have a stethoscope on order, but it won't be here for a week or two.
Any ideas?
Let the theories begin!
Thanks! - Jim M
Let's see what the brain-trust has for this:
I have a distinct tapping coming from the engine only when it's not loaded. At idle, in Park or Neutral, it's tapping about 200 times a minute. Put it in gear (forward or reverse) and the tapping stops.
Same thing when I driving at a medium speed: If the engine's unloaded I can hear the tapping echo off a curb or wall. However, if add the slightest bit of throttle or take my foot off the gas (negatively loading the engine) the tapping disappears.
I have a stethoscope on order, but it won't be here for a week or two.
Any ideas?
Let the theories begin!
Thanks! - Jim M
Last edited by scardini1; 08-16-2013 at 07:57 PM.
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scardini1 (08-16-2013)
#5
The following users liked this post:
scardini1 (08-16-2013)
#6
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Thanks guys. It's definitely coming from the engine compartment, but I'll remember the purge valve for future reference.
The cat? Hmmm,... that's interesting, because I've been getting P0430 (Left Cat efficiency low) for quite a while now, and its getting more frequent too. And the tapping echo does seem to be louder on the left than on the right. That could be it.
I am hoping it's the idler pulley though. I have to put a new S/C belt on sometime soon. With this many miles on the car (125K) should I just order new idler pulleys as well?
The cat? Hmmm,... that's interesting, because I've been getting P0430 (Left Cat efficiency low) for quite a while now, and its getting more frequent too. And the tapping echo does seem to be louder on the left than on the right. That could be it.
I am hoping it's the idler pulley though. I have to put a new S/C belt on sometime soon. With this many miles on the car (125K) should I just order new idler pulleys as well?
#7
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#9
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All good advice. Thanks. I took a look today. There are three idler pulleys - I'd probably replace (or rebuild?) all three.
However, the S/C idler pulley is right up against an electrical connection on the right radiator fan. If I figure out how to disconnect it, will there be room for any kind of normal wrench or breaker bar?
Has anyone ever tried inserting a piece of 1/2" bar stock and then just using a 1/2" open end wrench? (I "assume" it's 1/2"). I really hate the idea of pulling the fan for this.
However, the S/C idler pulley is right up against an electrical connection on the right radiator fan. If I figure out how to disconnect it, will there be room for any kind of normal wrench or breaker bar?
Has anyone ever tried inserting a piece of 1/2" bar stock and then just using a 1/2" open end wrench? (I "assume" it's 1/2"). I really hate the idea of pulling the fan for this.
#10
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I did my s/c tensioner and idler in my xj w/o removing the radiator. This is the tool that I used.
Serpentine Belt Tool Kit
Serpentine Belt Tool Kit
![](https://www.jaguarforums.com/forum/attachments/xk8-xkr-x100-17/51524-engine-tapping-when-unloaded-image_16281.jpg?dateline=1376893590)
#14
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I have 2 videos on my link that might help if it is related to the tensioner.
Link JagRepair.com - Jaguar Repair Information Resource
Link JagRepair.com - Jaguar Repair Information Resource
#15
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While nothing is impossible it's unlikely that placing it into gear would have any effect on a tensioner - chain or belt. Likewise an exhaust leak would probably get louder with the added load. Placing the transmission in gear provides a load against the torque converter which loads its bolts to one side, eliminating the clearance required to 'click'. Same would be true of a cracked flex plate. That's the reasoning behind my response.
#16
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