I have mentioned my car is knocking and thought I would throw a video on here to see what others might think the noise is. I am assuming a dropped valve. I tried to drag and drop the video here, but it says the type of file is not allowed. I went ahead and uploaded to Youtube. The link is below. I tried the hyperlink icon and it spit out the second line of text. I copied the link off of youtube for the first one. Don’t know if you will be able to click these after I post. You may have to paste into a browser. If there is a way to simply place a video here, the information would be fantastic. Thanks.
Okay, I guess the video posted itself twice no less. Now I get it. Thanks.
I am hoping to get a response or someone who will take the time to listen to my issue who may have some experience with this before I commit to yanking the entire engine apart. I have another entire engine in the garage and maybe it would behoove me to simply rebuild that motor. I guess if I can’t get a response maybe I am on the wrong site or am not following some etiquette?. Thanks
There are people who come to this site with a great deal of experience with Jaguar V12 engines, and I am sure one of them has heard your noise before. Your post is only one day old. Be patient.
Sounds like a dropped valve seat. I have heard the noise three times on three different 1984 V12 heads. Tapping increases with increase in rpms. You can confirm with a compression test, or better yet with a leakdown test (which will tell you if it’s intake or exhaust valve) SD Faircloth
My white 85 dropped a valve seat 5 yrs ago and it sounded similar though probably worse than one in video … ( seat was put back in place and pinned so it couldn’t drop again… )
Now 5 yrs later it still makes a similar click / tapping on warm up but the sound disappears after about 20 seconds … but it doesn’t always make a noise … if it’s started daily and engine is kept warm there’s no sound
If the engine is VERY cold the tapping is louder but soon Goes away
I put it down to a sticky valve due to a slight crud or xtra thick goop build up around valve seats ( tapping noise comes from front right side close to AC compressor )
I kick myself because I think I might have caused it by pulling the rubber pipe off ECU, causing it to run really rich … (the smoke out of exhaust was BLACK … embarrassed grin … it failed smog because of this and I got a “gross polluter” stamp on fail slip )
when I realized what was going on I assumed over rich fuel had left a carbon deposit on inlet valve seat, preventing it from fully closing ( because in addition to black smoke It would sometimes backfire which I assumed came from too much gas )
… to Remove residue on valve seat I poured about 1/3 bottle of fuel Lucas upper cylinder lubricant in tank which I continue to do. I was a bit pessimistic at first since I view bottled miracle cures as equivalent to band aids …but guess what ? … After about 1month backfire stopped. The tapping is sometimes still there for a few seconds on warm up, but since I have another XJS and the engines been rebuilt once I will keep moving forwards
Thanks for that information. I haven’t started tearing it down yet as I am still looking around to have a shop fab me up a head puller. I will also pull off the valve cover first. I am assuming the one of the valves will not come up all the way into its seat if the seat has fallen out and will also show less than full retraction under the cam? Also, how do you go about pinning a seat? Thanks.
Perform a compression test and report the readings.
If it is a valve seat, one would expect a loss of some compression since the seat would not seal gas tight.
pinning valve seat … hmmm … I think it’s a workshop trick where you take a punch and punch round the edge of the valve seat … aluminum expands and makes an even tighter interference fit at that point … or points … it was done on my 1985 5.3 about 5 yrs ago and I haven’t had a problem since, although nothing is guaranteed
Yeah, I recall that old saw. A bit inelegant, but, it works.
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A local machine shop, decades ago, showed me an example of a Corvair head done by the peen method. He was not complimentry! My Corvair had dropped a seat. It battered the head a bit. His solution was to send my head out for TIG welding to restore the alloy ands then machine a new recess for the seat.
He claimed his technique meant a tighter fit than the original GM method. Hot head and chilled seat. -
Another time, one of my old Ford V8’s blew a head gasket.
The combustion fire ate away some steel between bores. No way was a gasket going to seal with that hollow.
So, I used the peen method to raise the metal. Then filed it to the level of the surrounding metal. It worked, the gasket held.
- A more elegant pin is to drill very small holes in he seat and surrounding alloy. Tough as the seat is very hard. Then drive in small pins. Similar to the tappet “stake” on Jaguar I6 heads.
Carl .
Carl