What would a dropped valve seat sound like, and how loud would it be? What's the best way to tell? How easy is it for this to occur? Should it be a consistent sound or only noticeable when accelerating?

86 xjs 5.3.

Thanks very much.

 

It will be a rhythmic clacking sound coming from the vicinity of the valve cover. It may also be accompanied by rough idle.

Has the engine been seriously overheated?

 

yes the car overheated, but i caught it almost instantly. It got hot, no steam just bubbling in the coolant. It wouldnt have run hot for more than 10 seconds. Im not sure if this noise was there before, and im wondering if im being overly cautious here. Its a subtle but noticeable "ticking" coming from the front. Only upon acceleration and not at idle. No loss of power noticed and it idles fine.

I have a video of the noise but it seems to large to attach.

Do you agree that it would be unlikely for a valve to drop if it was caught early and wasnt really that serious? How loud would this "clacking noise" be do you think?

Runs very smooth and temp and oil pressure fine.

thanks.

 

It's pretty loud, like hitting the valve cover with a small hammer.

A light ticking noise under acceleration could simply be an exhaust leak or a cracked manifold. Not enough exhaust pressure to hear at idle, necessarily.

 

Okay, I think that sounds like good news. I'm thinking about putting a water pump lubricant and a Lucas product in the oil. Can't hurt.

But the dropped valve would most likely be heard at idle aswell? And it would be significantly loud correct? The idle would most likely be severely rough? If I accelerate slowly, the light ticking goes away. Also once once I'm past about 70kph it goes away entirely. Exhaust system looks good.


Anything else jumping out at you that I could try?

Sorry for all these questions! Your help is really appreciated! Thanks!

 

Ticking noise can also be electrical arcing across the distributor cap (I know because I have it on mine). An easy check for this is have a look with the engine running in the dark; blue sparks mean that the cap is cracked.
This may not be your problem but it is an easy check and one to tick off the list of possibilities.