87 911 carrera clatter after engine was hot

Booney1golf · 04-10-2009, 12:40 PM

I have an 87 911 3.2 that was rebuilt about 20,000 miles ago. I sat in my car idling for about 20 minutes when I started to leave I had clatter which sounded like bad gas. I run only Shell Premium from the same station and have never had this problem. After the car cooled down it has all but went away????

I have not noticed this before but I usually don't sit out idle for this long and my temp gage was above half way which was not that high??

Even though it does not seem to do this when I get in the car and drive immediately could this mean I might need my valves adjusted??

Thanks to all of you for your support and help thru the years!!

Booney1golf
87 911 Turbo look Cab - And I thought Golf was addicting

88-diamondblue · 04-10-2009, 01:02 PM

Did the sound come from the engine or transmission? The 87-89 have the G-50 trans which tends to have a rattle when idling. After rebuilding the engine I was very attuned to listening for strange noises. It rattled and I thought something in the engine was bad. Just the G-50 rattle. If you push the clutch in it will normally go away also.

The other possibility is a tensioner is starting to fail and with lower oil pressure from being at idle may have caused this. For that I would have your mechanic do a listen and see what he thinks.

old man neri · 04-10-2009, 03:17 PM

Could of had some sort of build up somewhere after 20 min of idling. You really shouldn't let your car just sit there idling for 20 min.

Zeke · 04-10-2009, 03:20 PM

Sounds like he had some detonation until the temps came down.

jurhip · 04-10-2009, 03:52 PM

I would start again, drive it to warm up then let it idle. Compare hot and cold sound. Also, verify hot and cold oil pressure readings at idle. It could be oil pressure related. But if it is, it would not take 20 min to happen. It would be linked to the oil pressure.

Though it's not great to let your car idle, 20 min will not cause damage that would result in a clatter.

Booney1golf · 04-13-2009, 08:28 AM

Update - I drove the car around 300 miles this weekend (top down - it does not get much better than this!!!) and the car ran as good or better than ever.

When I had the clatter it was not at idle only when giving it gas. If I eased into it, everything sounded normal, however if I gave it a little more gas then the clatter started. Probably not a good idea, but when I really accelerated, it also sounded normal. I also put the clutch in (during the time that the clattering was happening) and ran up the RPM's and everything seemed normal??

Anyway thanks to all of you for reading my Post and especially to you all that took the time to respond. I hope it does not come back. When it happened my heart sank, thinking $$$$$$$$$$$.

Best regards,
Booney1Golf
87 911 Turbo-Look Cab - And I thought Golf was addicting

uwanna · 04-13-2009, 10:10 AM

Many years ago, I had a similar problem with my '68 911. I got the engine very hot while in a miles long traffic jam on the way to Willie Nelson's 4th of July picnic, in Dripping Springs, Texas. (I said it was many years ago!!) Anyway, I abandoned the car by the side of the road rather than continue overheating it. Returned the next day and drove home. After that episode, I continued to drive the car for several days, but had the exact clatter noise you have.
I then went to a very good Pcar mechanic, who said, "I don't know what it is, but I would not drive it anymore, and I would tear it down to find the problem!"
Not to alarm you, but in tearing it down, I found a piston pin snapped in two, right in the center of the piston boss! Engine had been running fine, except for the clatter noise, just like yours.
With the snapped pin, the piston had been rocking, and wearing the cylinder to an oval.
I ended up getting new high comp 2.5 piston/cyl set from Ray Litz at Competition Enginering. Had him machine the case and heads, and did a complete rebuild. Had a nice little rocket after that (for it's day). I had never torn apart a Pcar motor before, so that little overheat episode was a great learning experience and prepared me for the eight 911s I've had since then.
If I were you, I would take your car to a real good Pcar mechanic, and get his opinion. Good luck
Grant

jurhip · 04-13-2009, 11:37 AM

Grant makes a good point about seeing a good P-car mechanic, but I would say go see several mechanics if you hear it again to get different opinions.

"Clatter" means different things to different people unless you are both hearing it, so its hard to diagnose. Also the cause of one clatter, as in Grant's case, does not mean its the cause of yours. I would not expect anything is broken in your car from a 20 min idling stint but I also don't know the full history of your car/motor.

In the meantime, keep an eye on oil consumption, power delivery and as always, noises.

timc · 04-13-2009, 12:00 PM

When my hydraulic tensioners began to fail, they would only rattle after the car had been driven for a while, and would rattle only right off of idle, like when pulling away. Was not related to oil pressure, the oil pressure was normal at the time of tensioner rattle. I've experienced many tensioner failures, not a big deal, but the noise from this one was so sporatic.

masraum · 12:13 PM

Quote:

Originally Posted by milt

Sounds like he had some detonation until the temps came down.

Quote:

Originally Posted by Booney1golf

Update - I drove the car around 300 miles this weekend (top down - it does not get much better than this!!!) and the car ran as good or better than ever.

When I had the clatter it was not at idle only when giving it gas. If I eased into it, everything sounded normal, however if I gave it a little more gas then the clatter started. Probably not a good idea, but when I really accelerated, it also sounded normal. I also put the clutch in (during the time that the clattering was happening) and ran up the RPM's and everything seemed normal??

Based on Booney's update, I think Milt is correct. Pinging/detonation happen under load. Having sit and idled for 20 minutes, the car would be HOT. Cars are more likely to ping/detonate when really hot. The only statement that seems contrary is "when I really accelerated, it also sounded normal". But that could be from either different fuel maps at full throttle or just the engine being louder making it harder to hear the pinging.

What fuel do you run in your carrera? 87, 89, 91/92/93? I'd always run the premium in it if I was you (especially in HOusTon, the heat here would definitely warrant premium), that should help. When was the last time it was tuned up/checked out? In the weather that we have had here recently, you should be able to sit and idle (but I recommend against it). I had an '88 and the temp would run up until the fan kicked on and that would save the temp from going super high. Maybe you need to check to see if your fan is coming on. That could cause a problem.

Are you aware of the temps for the lines on your temp gauge? IIRC, the 3.2L cars' temp gauges are roughly 150, 200, 250, 300 from the top down (in *F). (In C they are 60*, 90*, 120* and 150*).

This could have been from bad gas, but you need to run it down for sure before the weather gets hot.

jurhip · 04-13-2009, 12:49 PM

"when I really accelerated" could put the car into WOT fuel map or at least near it. The extra gas could help to cool the charge and prevent detonation.

Detonation under "lean" conditions is more likely anyway, which is where these cars run at part throttle.

keep listening for it, but Milt and Steve make good points.