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CorsePerVita
Joined: 25 Jul 2008
Posts: 1992
Location: Redmond, Oregon
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 Posted: Sat May 22, 2010 6:32 am Post subject: Heat exchanger seals |
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okay to sand down the heat exchanger ends with a sanding block to make a flat surface? or do i absolutely 100% need to take them in to get milled? 
do not want to take shortcuts, but if i can do it myself, I'd rather.
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- 1977 Porsche 924 2.0 N/A (Trackday Project)
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CorsePerVita
Joined: 25 Jul 2008
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Location: Redmond, Oregon
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| Posted: Fri May 28, 2010 11:46 am Post subject: |
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sanded them down and replaced the seals - no exhaust leaks - happy 914 once again 
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Rasta Monsta
Joined: 12 Jul 2006
Posts: 11733
Location: PacNW
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| Posted: Sat May 29, 2010 12:56 am Post subject: |
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Use copper locknuts, and DON'T overtighten.
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- WeiBe (1987 924S 2.5t) - 931 S3
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CorsePerVita
Joined: 25 Jul 2008
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Location: Redmond, Oregon
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| Posted: Sat May 29, 2010 1:56 am Post subject: |
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yeah that's what's on there - what is the torque rating on them exactly
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- 1977 Porsche 924 2.0 N/A (Trackday Project)
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CorsePerVita
Joined: 25 Jul 2008
Posts: 1992
Location: Redmond, Oregon
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| Posted: Sat May 29, 2010 2:04 am Post subject: |
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oh - you mean because i could strip the copper locknuts i assume... gotcha.
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- 1977 Porsche 924 2.0 N/A (Trackday Project)
- 1979 Porsche 924 2.0 N/A (The other daily)
- 1980 Porsche 931 (Daily)
- 1987 Lamborghini Jalpa
- 1999 Ducati 900SS |
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Rasta Monsta
Joined: 12 Jul 2006
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Location: PacNW
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| Posted: Sat May 29, 2010 2:36 am Post subject: |
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No, because the studs like to pull out of the head. No big deal to repair. . .with the heads off!
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fiat22turbo
Joined: 18 Jan 2006
Posts: 4040
Location: Portland, OR
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| Posted: Sat May 29, 2010 2:47 am Post subject: |
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That's why god created helicoils. It doesn't mean you should use them if you could avoid it 
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CorsePerVita
Joined: 25 Jul 2008
Posts: 1992
Location: Redmond, Oregon
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| Posted: Sat May 29, 2010 4:08 am Post subject: |
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| Rasta Monsta wrote: | | No, because the studs like to pull out of the head. No big deal to repair. . .with the heads off! |
oh that is way gay, i didn't know that. hmm, well i didn't torque them down to an insane amount, and used a short hand ratchet, they are snug. but not deathly torqued down. i wish i knew what the torque spec was so i knew if i was on the money or not. i noticed the stainless steel exchanger required a bit more oomph than the OEM exchanger to make a seal.
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- 1977 Porsche 924 2.0 N/A (Trackday Project)
- 1979 Porsche 924 2.0 N/A (The other daily)
- 1980 Porsche 931 (Daily)
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- 1999 Ducati 900SS |
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Rasta Monsta
Joined: 12 Jul 2006
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Location: PacNW
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| Posted: Sat May 29, 2010 4:14 am Post subject: |
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Those SS units are awesome, but will fry your starter. Make a heat shield.
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CorsePerVita
Joined: 25 Jul 2008
Posts: 1992
Location: Redmond, Oregon
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| Posted: Sat May 29, 2010 4:25 am Post subject: |
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so snug is plenty good then i assume? i guess i could attach a reducer on my torque wrench and get it out and see where i'm at. but it's definitely snug.
loving the ss exchangers - but the previous owner didn't flatten the tips of any of the exchangers so i had exhaust leaks out the wazoo. the leak may be on the opposite side since i can't hear much of one. it's a very faint leak - just enough to irk me beyond control. all the major ones are fixed. i am afraid to get the other side any tighter, i guess if i do need to i should just unseat it and grab new seals and try again just to be on the safe side.
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- 1977 Porsche 924 2.0 N/A (Trackday Project)
- 1979 Porsche 924 2.0 N/A (The other daily)
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- 1999 Ducati 900SS |
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TJC
Joined: 04 Apr 2010
Posts: 828
Location: Northwestern-ish Arizona, USA
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| Posted: Sat May 29, 2010 5:38 am Post subject: |
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Hope this may help, the spec for my Vanagon Type 4 is 15 foot pounds or 20 Nm. Unfortunately my 911 and 914 manuals don't give this spec. This same spec applies to the intake manifold to the head. I'd probably go just a tad lower as long as it seals and stays tight. You may want to use an inch pound wrench for better accuracy.
Make sure the copper nuts are still "locking" as used nuts will vibrate loose over time. When using new copper nuts I always made a habit of applying a small amount of anti-sieze on the threads to help "cut" the threads into the locking portion of the nut.
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CorsePerVita
Joined: 25 Jul 2008
Posts: 1992
Location: Redmond, Oregon
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| Posted: Sat May 29, 2010 6:00 am Post subject: |
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Definitely using more than 15lbs of force I believe. First side was a sinch, it's the SS side I'm having issues with. I am near 100% positive it's perfectly flat on the surface.
Although I have noticed that the SS exchanger opening has a thinner metal surface area than the other exchanger, so perhaps it is having a harder time making a 100% seal due to the surface area and potential angle?
Do the bolts pull out of the head overtime from overtightening, or as you tighten them as that is a concern :-/
So antiseize compound will help seal them? If that's the case then I will pull the exchangers off when I get home and do that. I assume you mean neverseize or something like that, you'd use it on spark plugs?
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- 1977 Porsche 924 2.0 N/A (Trackday Project)
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- 1980 Porsche 931 (Daily)
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- 1999 Ducati 900SS |
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TJC
Joined: 04 Apr 2010
Posts: 828
Location: Northwestern-ish Arizona, USA
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| Posted: Sat May 29, 2010 6:35 am Post subject: |
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| CorsePerVita wrote: | Definitely using more than 15lbs of force I believe. First side was a sinch, it's the SS side I'm having issues with. I am near 100% positive it's perfectly flat on the surface.
Although I have noticed that the SS exchanger opening has a thinner metal surface area than the other exchanger, so perhaps it is having a harder time making a 100% seal due to the surface area and potential angle?
Do the bolts pull out of the head overtime from overtightening, or as you tighten them as that is a concern :-/
So antiseize compound will help seal them? If that's the case then I will pull the exchangers off when I get home and do that. I assume you mean neverseize or something like that, you'd use it on spark plugs? |
First I would check your ss side to make sure that nothing is in a bind. If you did not losen the rest of the exhaust system, this will affect your seating at the head. Generally speaking, the exhaust system from the tailpipe back (In nearly every application that I can think of right off) should be loose at the joints until the heat exchanger, exhaust manifold, header...whatever...is at least snug to the head ensuring a good seal at the head. A binding situation and therefore a poor seal can occur if the system is "forced". This may be one cause of you having trouble with the ss side.
In regards to threads "stripping" or "pulling out", remember that the aluminum threads in the head are relatively "soft" and when the nut on the steel stud is being overtightened you are "pulling" the "hard" steel threads of the stud against the "soft" threads in the head and if you tighten too much then the soft threads will start to be torn away or "stripped" from the base material of the head. Basically the steel, with force, will overcome the aluminum.
The use of anti-sieze in my example is not for the benefit of sealing...you see NEW copper lock nuts have what could be described as a "crown" on them which is the locking device. This "crown" does not have threads cut into it when it is new, you are essentially "tapping" this part of the nut when you first install it, and that is my reason for using anti-sieze. This is not a big deal since copper is softer than steel, but anti-sieze makes the job of tapping easier. HOWEVER, this is exactly the reason that NEW copper exhaust nuts should be used every time the exhaust system comes apart at this point of fastening since once this area or "crown" is tapped, and the nut is taken off it basically is like any other non-locking nut and that is why they vibrate loose over time.
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'95 BMW 318i/5 ..."Pearl"
'87 Porsche 944 NA... "Liebchen"
'02 Porsche Boxster..."Sunbeam"
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CorsePerVita
Joined: 25 Jul 2008
Posts: 1992
Location: Redmond, Oregon
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| Posted: Sat May 29, 2010 6:48 am Post subject: |
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ok that makes good sense, thank you for the clarification! i will double check when i get home.
_________________
- 1977 Porsche 924 2.0 N/A (Trackday Project)
- 1979 Porsche 924 2.0 N/A (The other daily)
- 1980 Porsche 931 (Daily)
- 1987 Lamborghini Jalpa
- 1999 Ducati 900SS |
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CorsePerVita
Joined: 25 Jul 2008
Posts: 1992
Location: Redmond, Oregon
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| Posted: Sat May 29, 2010 3:13 pm Post subject: |
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I am just about to shoot this stupid thing - I thought I had it fixed. Sounded flawless.
Took it for a drive. Heard ONE pop.
Thought "awesome it's fixed!"
1 mile on my way back to home after the car is warmed up, decel.... POPOPPOPOOPOPOPOPOPOP.......
Pulled over, stuck it in neutral.... went to go hear under the car, sure as hell, unmistakable sound of exhaust leak.
_________________
- 1977 Porsche 924 2.0 N/A (Trackday Project)
- 1979 Porsche 924 2.0 N/A (The other daily)
- 1980 Porsche 931 (Daily)
- 1987 Lamborghini Jalpa
- 1999 Ducati 900SS |
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