Heavy head rattle - dropping revs

Christopher

Christopher

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I took my car out this morning for a beautiful summer’s day drive, windows down, sunroof open. With all the noise I carelessly didn’t notice I was still in third gear whilst hammering along at 90mph – Doh.

Next thing rattling noise from the engine, so I pull over for closer inspection.

As I slow down the revs drop with clutch in to about 2000 and almost stalling before letting the clutch back out and rising to just 7000.

Rattling coming from cylinder head. Got it home and removed. Given the intensity of the rattle was expecting a broken spring or rocker arm, but all seemed OK. Checked the banjo bolts on the oil rail (correctly fitted forwards) and nice and tight.

Back from garage now and investigations here point me towards checking the chain tensioner valve – and having the issue with the dropping revs this seems a sensible next step.



Any other clues as to what my reckless driving may have caused with my noise and rev symptoms, and what else to check when I’m back at my garage tomorrow ?
 
At 7000 RPM with single valve springs I would guess you had a serious valve float and I would be looking to see if bent valves
I would do a compression test
 
With a 3.64 diff, and a 4 speed trans, 92 mph is 6250 RPM, so just above redline. I'd start with the tensioner first. Make sure it is properly primed. If you crashed a valve, I would expect it would not have made the drive home... But do a compression test too...
 
ScottAndrews said:
With a 3.64 diff, and a 4 speed trans, 92 mph is 6250 RPM, so just above redline. I'd start with the tensioner first. Make sure it is properly primed. If you crashed a valve, I would expect it would not have made the drive home... But do a compression test too...
Click to expand...
Only US got the 3.64, a CSi has a 3.25 diff.
 
Thanks All -

Don - thanks for the advice. I've taken a look but if there's a break in one it's not obvious. I'll revisit tomorrow
Boonies / Scott - i've checked the tensioner and all seems OK. The rattle does appear to be coming from the front of the head, but it's difficult to tell.

Appreciate the advice - will try again tomorrow to find the culprit
 
did you use a screw driver to depress the piston?


Note that an old chain guide is very brittle and could have broken a chunk loose

Borescope time.
 
No harm in starting the engine with the valve cover off, just prepare yourself for oil spatter. You can use some cardboard to keep things contained. Doing so may allow you to better identify the position, if not the source, of the rattle.
 
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