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Discussion Starter · #1 ·
Two days in a row now, only after the car has been sitting in the sun for 8+hours, when I started it I could here a rata-tat-tat noise coming from the engine compartment. At first I wondered if it was bearings going in one of the pulleys but it was not that type of sound. I then thought it may be coming from the valve cover/timing chain cover on the passenger side, maybe like a loose bicycle chain riding the chain guard. It lasted about 30 seconds before a louder tapping noise and then like that, its gone and everything is normal. Oil pressure is indicating O.K., guides apparently looked fine last time motor was opened about 3000km ago.....and it is not happening all the time, only those two times after sitting in the sun all day at work? Would the tensioner not be functioning properly right at start up?

I am not sure what to do next, I am new to these cars. Any insight or advice you guys can give me is appreciated.

Thanks, Kyle...
 

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1991 500SEC 55K mi. 1987 560SEC Now 153K mi. 2020
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You've recently acquired this car. V8 T/chains need to be changed at the 100K miles mark. It might be a really good idea to check out the T/chain, guide rails & tensioner... Sounds as though you have a ticking time bomb there.....

Look for Ben_Twombley's great picture posting on his timing chain.

Good luck, MBL
 

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1991 500SEC 55K mi. 1987 560SEC Now 153K mi. 2020
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Take a look in the DIY section. There are some scary photos of the plastic bits I refer to. If your guides are that color... whoa baby!

:eek:) MBL
 

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Discussion Starter · #6 ·
Read BenTwombley`s diagnosis post after searching the forum...Very good reading. Upon leaving for work this morning at 5am, I started the car and no sound, nice and normal....Then when I left work this afternoon after the car had been sitting in 25ish Celsius sun all day, the noise was there again. Upon closer inspection, it sounds like a fan blade tapping against something, it speeds up with the engine and slows with it too...It goes for 30-60seconds then right before it disappears it sounds like an air valve quickly letting off pressure. I am wondering if it may be part of the HVAC system or maybe the engine cooling system...Is this possible? BTW, if it makes any difference, the AC compressor currently has no belt or R134 charge....

That is the kicker for me though, only on cold starts after sitting in the sun and the fact that it makes that pfffftt pressure relief sound right before it stops...

Any clues or am I still likely looking at a timing issue???

Thanks again
Kyle
 

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Sounds EXACTLY like timing... You are playing with a 5K time bomb by continuing to drive the car.

The oil line clips look OLD and cooked..typically one does those when the chain/rails/tensioner are replaced so if I had to wager I'd say your's have not beed done.

Went to the bone yards today..Say NO LESS then 5 116's/117's w/ cracked valve covers/jumped timing.

Were it my car I would have done the job yesterday.

Jonathan
 

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Discussion Starter · #8 ·
Ran the problem by both of my mechanics and they each think it is the air pump located down infront of the engine. Told me to unplug the wiring harness from it and see if the noise is there when I start it again.

I am liking the sound of this diagnosis for obvious reasons. I will let you know what happens.

Kyle
 

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Discussion Starter · #9 ·
I only knew it was coming from the front right, and to be honest did not know the air pump existed. Tried unplugging it and no noise. Plugged it in and there it was again.

Am I better off to run with it unplugged until it is repaired or should I just deal with the noise. Anything I can do with it in the meantime ie; lube, oil or is it just something that needs to be replaced immediately?

Thanks again....
 

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the air pump is dispensable, so it's your call about whether or not you unplug it.
 
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