Air Pump Removal: Hole Plugs
05-14-2009, 11:34 PM
#1
Drifting
Thread Starter
Air Pump Removal: Hole Plugs
I have removed my air pump and the associated plumbing, back to the pipe for the cats.
However, the cats have not been removed (yet). I may want to re-install the cats and the pump in the future, or the next owner may live in a more emisisons restrictive state, so I do not just want to crimp over the pipe coming from the cats that ran to the air pump.
So:
1. What is the thread size for the end of the pipe so I can look for a cap to screw on to avoid an odd sounding exhaust leak ? Any sources or other suggestions for this?
2. What has been used to cap the intake the the bottom of the air filter/box that is now left open? I can imagine anything from tin foil held on by a pony tail holder up to a fine CNC machined Delrin cap. However, all my daughters pony tail holders are pink, so they would clash, and I misplaced my three axis CNC machine.
I read what links I could find, and they seemed mostly concerned about making the belts fit on the older cars and the effect on the cats and the emissions.
I did run into this:
https://rennlist.com/forums/928-foru...-question.html
where the bottom of a chair leg was used to block the hole on the filter housing.
Those of you who have removed everything, what did you use?
-Ken
However, the cats have not been removed (yet). I may want to re-install the cats and the pump in the future, or the next owner may live in a more emisisons restrictive state, so I do not just want to crimp over the pipe coming from the cats that ran to the air pump.
So:
1. What is the thread size for the end of the pipe so I can look for a cap to screw on to avoid an odd sounding exhaust leak ? Any sources or other suggestions for this?
2. What has been used to cap the intake the the bottom of the air filter/box that is now left open? I can imagine anything from tin foil held on by a pony tail holder up to a fine CNC machined Delrin cap. However, all my daughters pony tail holders are pink, so they would clash, and I misplaced my three axis CNC machine.
I read what links I could find, and they seemed mostly concerned about making the belts fit on the older cars and the effect on the cats and the emissions.
I did run into this:
https://rennlist.com/forums/928-foru...-question.html
where the bottom of a chair leg was used to block the hole on the filter housing.
Those of you who have removed everything, what did you use?
-Ken
05-15-2009, 11:33 AM
#2
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The correct caps are available from Porsche for about $30 each - ouch!
It does not give the thread details - sorry.
Roger
It does not give the thread details - sorry.
Roger
__________________
Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission?
George Layton March 2014
928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission?
George Layton March 2014928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
05-15-2009, 11:59 AM
#3
Team Owner
you could go to home depot plumbing department , and buy a selection of brass caps find one that screws on and that should be good, use brass as its softer so it will give if the threads are not perfect
05-15-2009, 12:02 PM
#4
Drifting
Thread Starter
Roger,
You are the man!
Do you mean caps for the filter housing or for the exhaust pipe? ( or both?) You say threads, so I assume exhaust.
I am going to poke around the local hardware store to see if there is anything that could substitute.
If not, and barring better suggestions from others, I may add the $30 caps to a rather large order for you I am putting together. Hint: That order may make the exhaust pipe cap question moot.
Best,
-Ken
You are the man!
Do you mean caps for the filter housing or for the exhaust pipe? ( or both?) You say threads, so I assume exhaust.
I am going to poke around the local hardware store to see if there is anything that could substitute.
If not, and barring better suggestions from others, I may add the $30 caps to a rather large order for you I am putting together. Hint: That order may make the exhaust pipe cap question moot.
Best,
-Ken
05-15-2009, 12:07 PM
#5
Drifting
Thread Starter
MrMerlin,
Sorry, your response came in as I was replying to Rog. I am leaning that way too for the exhaust. A "close size" brass cap ( metric caps in a US harware plumbling aisle would be "unlikely").
What would you think of coating the steel threads with a wax or release compound ( vaseline ) and then JB welding the "close size" cap on? It would then prevent leaks and odd exhaust noises and still, in theory, be removable. Just brainstorming, and with any luck, the situation with the exhaust would be only temporary.
-Ken
Sorry, your response came in as I was replying to Rog. I am leaning that way too for the exhaust. A "close size" brass cap ( metric caps in a US harware plumbling aisle would be "unlikely").
What would you think of coating the steel threads with a wax or release compound ( vaseline ) and then JB welding the "close size" cap on? It would then prevent leaks and odd exhaust noises and still, in theory, be removable. Just brainstorming, and with any luck, the situation with the exhaust would be only temporary.
-Ken
05-15-2009, 12:11 PM
#6
Race Car
MrMerlin,
Sorry, your response came in as I was replying to Rog. I am leaning that way too for the exhaust. A "close size" brass cap ( metric caps in a US harware plumbling aisle would be "unlikely").
What would you think of coating the steel threads with a wax or release compound ( vaseline ) and then JB welding the "close size" cap on? It would then prevent leaks and odd exhaust noises and still, in theory, be removable. Just brainstorming, and with any luck, the situation with the exhaust would be only temporary.
-Ken
Sorry, your response came in as I was replying to Rog. I am leaning that way too for the exhaust. A "close size" brass cap ( metric caps in a US harware plumbling aisle would be "unlikely").
What would you think of coating the steel threads with a wax or release compound ( vaseline ) and then JB welding the "close size" cap on? It would then prevent leaks and odd exhaust noises and still, in theory, be removable. Just brainstorming, and with any luck, the situation with the exhaust would be only temporary.
-Ken
Dan
'91 928GT S/C
475hp/460lb.ft
05-15-2009, 12:17 PM
#7
Drifting
Thread Starter
Dan,
You are probably right, the JB weld would either do what it does best, and HOLD, or the release agent would make it ineffective.
Im not so worried about it coming off, as a close fit ( crossthreading english to metric threads for instance) and any adhesive will make that unlikely, but I want it sealed and eventually removable. I don't think the Locktite would seal it all that well, and may not stand up to the temperature.
What about a high temp silicone? Are there versions that will stand up to exhaust temperatures? Or maybe thick layers of teflon thread tape, that stuff is pretty tough?
-Ken
You are probably right, the JB weld would either do what it does best, and HOLD, or the release agent would make it ineffective.
Im not so worried about it coming off, as a close fit ( crossthreading english to metric threads for instance) and any adhesive will make that unlikely, but I want it sealed and eventually removable. I don't think the Locktite would seal it all that well, and may not stand up to the temperature.
What about a high temp silicone? Are there versions that will stand up to exhaust temperatures? Or maybe thick layers of teflon thread tape, that stuff is pretty tough?
-Ken
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05-15-2009, 12:20 PM
#8
Race Car
Dan,
You are probably right, the JB weld would either do what it does best, and HOLD, or the release agent would make it ineffective.
Im not so worried about it coming off, as a close fit ( crossthreading english to metric threads for instance) and any adhesive will make that unlikely, but I want it sealed and eventually removable. I don't think the Locktite would seal it all that well, and may not stand up to the temperature.
What about a high temp silicone? Are there versions that will stand up to exhaust temperatures? Or maybe thick layers of teflon thread tape, that stuff is pretty tough?
-Ken
You are probably right, the JB weld would either do what it does best, and HOLD, or the release agent would make it ineffective.
Im not so worried about it coming off, as a close fit ( crossthreading english to metric threads for instance) and any adhesive will make that unlikely, but I want it sealed and eventually removable. I don't think the Locktite would seal it all that well, and may not stand up to the temperature.
What about a high temp silicone? Are there versions that will stand up to exhaust temperatures? Or maybe thick layers of teflon thread tape, that stuff is pretty tough?
-Ken
Dan
'91 928GT S/C
475hp/460lb.ft
05-15-2009, 01:42 PM
#10
Drifting
Thread Starter
My reading of the lug nuts fix was that they fit the test bung on the pipe/header. I think the cat pipe is too large for a lug nut, but I will certainly check when I get home.
If not, off to the hardware store and auto supply for close fit cap and suitable goop to hold and seal it.
Any suggestions on a good looking plug for the air filter housing? That will be more permanent and more obvious, so it is more critical.
-Ken
If not, off to the hardware store and auto supply for close fit cap and suitable goop to hold and seal it.
Any suggestions on a good looking plug for the air filter housing? That will be more permanent and more obvious, so it is more critical.
-Ken
05-15-2009, 06:18 PM
#11
Drifting
Thread Starter
Took measurements with my trusty caliper:
O.D. of Cat pipe fitting, edge of threads: 0.860 inches. ( way too big for lug nut)
O.D. of fitting for filter housing: 0.766 inches. If I can find a 3/4" chair leg cap or cane/crutch end, it may be perfect.
-Ken
O.D. of Cat pipe fitting, edge of threads: 0.860 inches. ( way too big for lug nut)
O.D. of fitting for filter housing: 0.766 inches. If I can find a 3/4" chair leg cap or cane/crutch end, it may be perfect.
-Ken
05-15-2009, 06:28 PM
#12
Addict
Rennlist Member
Rennlist Member
For the air filter housing I bought a big pack of caps at Autozone or Kragen and there was one that was perfectly sized for this. I think it may have been in the Help! brand section.
05-16-2009, 08:39 PM
#13
Drifting
Thread Starter
Okay, here are the solutions I found:
For the Air Box, the solution was easy, I followed the advice of devilinblack and went to the "Help" parts area of my local Advance Auto and found part# 02254, which is a pack of two 3/4 inch rubber plugs, technically "Bypass Caps". Fit perfectly,look great and problem solved for about $3.50
For the Cat Pipe, I took my Calipers into the plumbing aisle at Lowe's and found that a 3/4" cooper cap has an ID of about .870" ( remember it fits OVER 3/4" copper pipe). This fit very well over the cat pipe end. I sealed it with the high temp (700 deg.) cooper looking Silicone and held it in place with a small sheet metal set screw for extra security. Total cost, about $0.75 plus glue and screw.
My only concern is that either the pipe will get above 700 deg, or that the pressure will overcome the limits of the set screw and glue. In that case I am out one $0.75 piece of copper, and I will try again, but this time would use muffler repair putty, which will certainly hold, but may be impossible to remove. I'll post more on the durability after I get a few miles on it.
-Ken
For the Air Box, the solution was easy, I followed the advice of devilinblack and went to the "Help" parts area of my local Advance Auto and found part# 02254, which is a pack of two 3/4 inch rubber plugs, technically "Bypass Caps". Fit perfectly,look great and problem solved for about $3.50
For the Cat Pipe, I took my Calipers into the plumbing aisle at Lowe's and found that a 3/4" cooper cap has an ID of about .870" ( remember it fits OVER 3/4" copper pipe). This fit very well over the cat pipe end. I sealed it with the high temp (700 deg.) cooper looking Silicone and held it in place with a small sheet metal set screw for extra security. Total cost, about $0.75 plus glue and screw.
My only concern is that either the pipe will get above 700 deg, or that the pressure will overcome the limits of the set screw and glue. In that case I am out one $0.75 piece of copper, and I will try again, but this time would use muffler repair putty, which will certainly hold, but may be impossible to remove. I'll post more on the durability after I get a few miles on it.
-Ken
Last edited by KenRudd; 05-16-2009 at 08:39 PM. Reason: typo
05-16-2009, 09:20 PM
#14
I would like to make my 84' emissions legal again. The PO removed the cat and cut off the air tube about 24" from where it would attach to the cat. The air pump has been gutted too. Guess I need to find a parts car with these items still intact. I could get one of the new generation cats that don't require air to be pumped into them. They are actually pretty inexpensive from Sumitt Racing.
05-17-2009, 09:28 AM
#15
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My air pump was disconnected by the previous owner by removing the belt.
Appart from the anti-pollution effect that is hard to measure, the most noticeable effect of the removal was the center console getting hot from excessive heat generated by the cats down under. It was sufficiently hot so that the A/C cold air was barely keeping the cockpit comfortable during hot days. The other problem was the "CAT TEMP TOO HIGH" warning going off from time to time (originating from Japan, my car has 2 temperature probes in the CATs).
I decided to rebuild the the air pump and reconnected it. The CATs temperature is now more normal. The center console heat is no longer a problem. I also noticed that some water/humidity (car washing)was flowing through the pump air intake and rust had built up in the pump. Fortunatly, the pump bearings were untouched and I managed to clean the thing up. So if you plan to leave yourself the option to reconnect the pump, make sure the tubings are properly sealed.
Also I'm not sure if the CATs can be damaged from running warmer than normal. I think it is something to consider before removing the air pump system.
This is an opinion based on my observations. I may be technically wrong...
Michel.
89 928 S4 ROW
Appart from the anti-pollution effect that is hard to measure, the most noticeable effect of the removal was the center console getting hot from excessive heat generated by the cats down under. It was sufficiently hot so that the A/C cold air was barely keeping the cockpit comfortable during hot days. The other problem was the "CAT TEMP TOO HIGH" warning going off from time to time (originating from Japan, my car has 2 temperature probes in the CATs).
I decided to rebuild the the air pump and reconnected it. The CATs temperature is now more normal. The center console heat is no longer a problem. I also noticed that some water/humidity (car washing)was flowing through the pump air intake and rust had built up in the pump. Fortunatly, the pump bearings were untouched and I managed to clean the thing up. So if you plan to leave yourself the option to reconnect the pump, make sure the tubings are properly sealed.
Also I'm not sure if the CATs can be damaged from running warmer than normal. I think it is something to consider before removing the air pump system.
This is an opinion based on my observations. I may be technically wrong...
Michel.
89 928 S4 ROW