Thermal reactor location & engine sound
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Joined: Nov 2004
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From: Cartersville, GA
Thermal reactor location & engine sound
Does a '75 911 ROW engine have the thermal reactors? If so, where are they located? I believe I read that they are in the header system somewhere. My original headers which I plan to replace with SSI's don't look to have any 'extra' components....bolt directly to the engine, run through a euro pre-muffler, then muffler. I haven't taken them off yet to look inside though.
Engine sound...I've finally got the engine running and tunned up (big milestone). I've noticed a sound when cold coming from the air box which sounds like a bad bearing (originally I thought it was coming from the fan but it is not). I've concluded that it must be the pistons riding in the chambers sounding dry. I do have plenty of oil...now about 11 quarts of 20W50. I let the engine run until it was warmed up and the sound went away. Checked oil and it is between the marks when warmed up and oil must be circulating as the inlet / outlet hose / tube were warm by touch. Is this a normal sound with the engine cold?
Thanks for any input in advance.
Engine sound...I've finally got the engine running and tunned up (big milestone). I've noticed a sound when cold coming from the air box which sounds like a bad bearing (originally I thought it was coming from the fan but it is not). I've concluded that it must be the pistons riding in the chambers sounding dry. I do have plenty of oil...now about 11 quarts of 20W50. I let the engine run until it was warmed up and the sound went away. Checked oil and it is between the marks when warmed up and oil must be circulating as the inlet / outlet hose / tube were warm by touch. Is this a normal sound with the engine cold?
Thanks for any input in advance.
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From: Virginia
I believe thermal reactors were only installed on 76/77 2.7 liter engines that were destined for the US market. Thermal reactors were Porsche's crude attempt to comply with the US's tightening emmissions standards back in the 1970's.
Thermal reactors were bolted directly to the cylinder heads, like exhaust headers on normal cars.
I would suggest taking the car to a Porsche wrench and let them listen to your noise after the car sits overnight. Very hard to id a cold start noise by your description. As a point of reference, neither of my 911's make the type of sound you describe when started cold.
Thermal reactors were bolted directly to the cylinder heads, like exhaust headers on normal cars.
I would suggest taking the car to a Porsche wrench and let them listen to your noise after the car sits overnight. Very hard to id a cold start noise by your description. As a point of reference, neither of my 911's make the type of sound you describe when started cold.
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From: Bakersfield, CA, for now...
Bruce is right, thermal reactors bolt, using three flanges each, directly to the cylinder head exhaust ports. They look like a tube, closed off at each end, they are about 3" in diameter and a little over a foot long. They were used on CA cars beginning with '75 models (they are pictured on page 63 of my book), but were not used on ROW cars. You're safe...
The noise you describe, are you listening with the air filter and its cover installed, or off? With the filter off you can clearly hear more injection/engine related noises. Again, Bruce is right, if you have a valid concern you should leave your car with a Porsche shop, overnight, and let them listen to it in the am. Also, to be sure the noise is not fan/alternator related, remove the alternator belt one evening and start the car without it the next morning. Noise gone? You've found your culprit. Noise still there? Alt/fan are OK...
Pete
The noise you describe, are you listening with the air filter and its cover installed, or off? With the filter off you can clearly hear more injection/engine related noises. Again, Bruce is right, if you have a valid concern you should leave your car with a Porsche shop, overnight, and let them listen to it in the am. Also, to be sure the noise is not fan/alternator related, remove the alternator belt one evening and start the car without it the next morning. Noise gone? You've found your culprit. Noise still there? Alt/fan are OK...
Pete
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Joined: Nov 2004
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From: Cartersville, GA
I am listening with the air filter / cover removed. When air filter / cover are installed and deck lid closed, the sound is definately more difficult to hear. I'm not overly concerned about the noise, just curious if anyone else had noticed it before as these engines have alot of expanding to do before the pistons and heads start to close their gap.
Glad to hear no thermal reactors.
By the way Pete, I started my emergency brake job last night (my cable broke when I was attempting to adjust). I haven't disassembled everything yet but with the rotor off I don't see any broken expansion plates. I'll have to continue to investigate. Maybe I'll bring up that old thread once I figure what's wrong for others to reference.
Paul
Glad to hear no thermal reactors.
By the way Pete, I started my emergency brake job last night (my cable broke when I was attempting to adjust). I haven't disassembled everything yet but with the rotor off I don't see any broken expansion plates. I'll have to continue to investigate. Maybe I'll bring up that old thread once I figure what's wrong for others to reference.
Paul
