chain noise when hot

rgmrgm · 05-31-2011, 04:16 PM

i have been experimenting with a fire damaged engine. i have it running fairly well, no smoke or leaks but i am concerned with what sounds like chain noise when the engine is hot. no noise on acceleration but slight rattle when i let off the throttle. sounds like a tensioner may be allowing slack when hot. it has oil fed tensioners so i am concerned that there may be an oil restriction or internal leak, pressure is good. how can i test a tensioner for a hot running problem, by the time i remove the muffler and expose it, it will be cooled down. any suggestions?
the fire damaged the rubber portion of oil line to the right chain housing so i replaced the line. it appears the fire was most intense in the right chain housing area. i think i will replace the left line and both tensioners

DRACO A5OG · DRACO A5OG's Garage

Have you removed the covers to take a look at the rails, I believe they are made of some plastic. May have melted or damaged them with the heat from the fire?

rgmrgm · 05-31-2011, 04:36 PM

would one or more bad rails only make noise when hot, the engine sounds perfect on a cold start (80 degrees) and remains so for a couple of miles then the noise gradually starts and gets worse as the engine gets hotter. can you believe the cd unit works fine pretty tough construction

DRACO A5OG · DRACO A5OG's Garage

OMG!, wow.

Well you never know until you open her up. Will be easier with the engine out.

rgmrgm · 06-02-2011, 05:19 PM

prior to putting this engine together i inspected the tensioners, oil fed, they were tight, good clearance, no signs of excessive wear. runs great when cold but i hear chain noise when its hot and i get off of the throttle, no noise while under load. today i changed the tensioners. left side was very stiff could hardly compress it with channel lock pliers so i secured the chain and pulled it out. i could not compress it with my thumb so i put it in a vise and as i compressed it oil came out from under the hardened cap on the piston not from the hole where grenade pin goes. put two new tensioners and lines in. now it runs like an old sc and only makes those noises 911's are supposed to make. this is new to me a tensioner being too tight. i should take it apart to see what caused this but at least i am on the road again with a "hot" engine

911Freak · 06-02-2011, 07:17 PM

Man that's one tough little SC you got there

. Glad to hear you got it sorted!

Please snap a few pics of the tensioner and what you find 'on the inside', I'd be very interested to see if the little o ring inside is deformed from the heat from the fire.

What was the fire from?

Again, nice save!

kidrock · 06-03-2011, 10:01 AM

is that a Dunkel Blau? What a survivor....I like hearing stories like this.

rgmrgm · 06-03-2011, 10:47 AM

i took the piston and spring out of the tensioner can't see any problems. i did not know how to go any further. the bottom has a snap ring but after removal the bottom would not press out. the top has what looks like a ball valve that is pressed in. engine sure idles smoother with the new tensioners. i guess the tensioners, when working properly,allow the chain to bounce while maintaining a certain level of tension. we know the problems with a loose chain but if the chain is too tight it can also cause problems. seems to work ok after i put it back together. pic is out of focus but you can see the oil forced out under the hardened cap when compressed.

Jonny042 · Jonny042's Garage

It strike me that there is nothing to go wrong here.... everything I've read indicates to me that there is no such thing as a failed hydraulic tensioner?

But you're saying you think the tensioner was too tight? And there really is a difference in the way it runs, sounds, and idles, with the new tensioners. Interesting.

I have my engine out, one of the "while I'm in there" things I'm up to is replacing the tensioners, just because occasionally there are noises from the engine that I don't care of (when hot, like yours). So just to be sure the new tensioners are going in.

Based on your results I'm looking forward to seeing how she runs after.

rgmrgm · 06-04-2011, 05:38 AM

i suspect the tensioner problem i had was related to the engine fire, but i cannot believe how much better it runs and sounds with new tensioners. its like resealing the cis system w/ new injector and sleeve o-rings makes them run like new engines

Jonny042 · Jonny042's Garage

Well, I changed mine out today, and I can say I'm not sure if it was money well spent or not... time will tell. Motor will hopefully be back in the car in a week or so.

What I can say is that the new tensioners are indistinguishable from the old ones (other than a little cleaner on the outside). Same amount of force required to compress them (after "collapsing" the old ones in the vise)... other than that there's nothing to compare.

rgmrgm · 06-04-2011, 05:55 PM

i physically removed four tensioners from two engines i have and additionally tested two new tensioners that had never been installed or pumped up. once the oil is out of the tensioners they all can be compressed with strong thumb pressure. even the one i suspect is bad can now be compressed with strong thumb pressure after i put it back together. the difference was the amount of force required to compress the four that had oil in them three required channel lock pliers and a vice to completely evacuate the oil and the oil came out of the grenade pin hole. on one channel lock pliers would not compress it and strong vice pressure was required and the oil came out from under the cap on the piston. i put the two new ones in and the chain noise when hot is gone and the car is running "seat of the pants" better