| Author |
Message |
AB westy nut
Samba Member
Joined: June 01, 2010
Posts: 1124
Location: Calgary, Alberta
|
 Posted: Tue May 23, 2017 8:47 am Post subject: PSA on vacuum leaks - check your intake manifold nuts! |
 |
|
Hey guys,
Been a while since I've posted anything. I took the bus out of hibernation yesterday and did all of the pre-camping maintenance like valve check/adjustment, oil change, dwell and timing check. Towards the end of last season I was noticing the idle speed creeping up, especially when warm. I did a cursory check of all the vacuum hoses and they were all fine (keep in mind, the motor was fully rebuilt 4000 miles ago) so I put it on my list of things to check in the spring. So in my process yesterday, I re-torqued the intake manifold nuts and found that every single one was loose. I'm guessing no more than 5 ft-lbs each. The engine now settles into a perfect 900 rpm idle. So I just thought I'd throw it out there in case anyone is having trouble tracking down a vacuum leak.
Can't wait to get out there!
_________________
1963 Ruby Red 356 Cabriolet
1976 Sage Green Westfalia Deluxe |
|
| Back to top |
|
 |
raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21511
Location: Oklahoma City
|
| Posted: Tue May 23, 2017 1:52 pm Post subject: Re: PSA on vacuum leaks - check your intake manifold nuts! |
|
|
| AB westy nut wrote: |
Hey guys,
Been a while since I've posted anything. I took the bus out of hibernation yesterday and did all of the pre-camping maintenance like valve check/adjustment, oil change, dwell and timing check. Towards the end of last season I was noticing the idle speed creeping up, especially when warm. I did a cursory check of all the vacuum hoses and they were all fine (keep in mind, the motor was fully rebuilt 4000 miles ago) so I put it on my list of things to check in the spring. So in my process yesterday, I re-torqued the intake manifold nuts and found that every single one was loose. I'm guessing no more than 5 ft-lbs each. The engine now settles into a perfect 900 rpm idle. So I just thought I'd throw it out there in case anyone is having trouble tracking down a vacuum leak.
Can't wait to get out there! |
Do you use the spring washer underneath the nuts?
I know in the 411/412 book they list a spring washer of part # N 12 2412 2 (8mm Id and 15mm OD).
Over the years many 1.7 and 1.8 that have had extensive dealer work I have found using a very thin flat washer and an old school, tab type self-locking nut (part # 113 415 431 A) which is actually a 14mm outside hex with 8mm ID.
Its the same part # that is used to hold my strut mounts.
It was odd to find them there...but they work much better, do not come loose and were available from the dealer.
The stock spring washer works well but must be replaced at every gasket change. The heat takes the spring tension out of them. Ray |
|
| Back to top |
|
|
curtp07
Samba Member
Joined: November 28, 2007
Posts: 874
Location: Mass
|
| Posted: Tue May 23, 2017 8:04 pm Post subject: Re: PSA on vacuum leaks - check your intake manifold nuts! |
|
|
Good tip thanks!
_________________
Subaru |
|
| Back to top |
|
|
airschooled
Air-Schooled
Joined: April 04, 2012
Posts: 12721
Location: on a bike ride somewhere
|
| Posted: Tue May 23, 2017 9:23 pm Post subject: Re: PSA on vacuum leaks - check your intake manifold nuts! |
|
|
I have yet to work on a bus with all eight at proper spec. I'm starting to recommend a torque check on those at every oil change.
_________________
Learn how your vintage VW works. And why it doesn't!
One-on-one tech help for your Volkswagen:
www.airschooled.com |
|
| Back to top |
|
|
Abscate
Samba Member
Joined: October 05, 2014
Posts: 22639
Location: NYC/Upstate/ROW
|
| Posted: Wed May 24, 2017 3:33 am Post subject: Re: PSA on vacuum leaks - check your intake manifold nuts! |
|
|
Need to summarize the correct torque for single and dual port intake manifold and dual carb riser nuts to complete this thread.
I first read this, thought the mantra about heat was ridiculous, saw author ray, said to myself...uh oh, what am I not getting right?
Then I realized I was thinking about the carb to manifold nuts, not the manifold to cylinder head nuts.
The best part of getting old isn't that you know everything...you don't....but you get better at recognizing those that do and those that don't.
_________________
.ssS! |
|
| Back to top |
|
|
AB westy nut
Samba Member
Joined: June 01, 2010
Posts: 1124
Location: Calgary, Alberta
|
| Posted: Wed May 24, 2017 8:43 am Post subject: Re: PSA on vacuum leaks - check your intake manifold nuts! |
|
|
| raygreenwood wrote: |
| AB westy nut wrote: |
Hey guys,
Been a while since I've posted anything. I took the bus out of hibernation yesterday and did all of the pre-camping maintenance like valve check/adjustment, oil change, dwell and timing check. Towards the end of last season I was noticing the idle speed creeping up, especially when warm. I did a cursory check of all the vacuum hoses and they were all fine (keep in mind, the motor was fully rebuilt 4000 miles ago) so I put it on my list of things to check in the spring. So in my process yesterday, I re-torqued the intake manifold nuts and found that every single one was loose. I'm guessing no more than 5 ft-lbs each. The engine now settles into a perfect 900 rpm idle. So I just thought I'd throw it out there in case anyone is having trouble tracking down a vacuum leak.
Can't wait to get out there! |
Do you use the spring washer underneath the nuts?
I know in the 411/412 book they list a spring washer of part # N 12 2412 2 (8mm Id and 15mm OD).
Over the years many 1.7 and 1.8 that have had extensive dealer work I have found using a very thin flat washer and an old school, tab type self-locking nut (part # 113 415 431 A) which is actually a 14mm outside hex with 8mm ID.
Its the same part # that is used to hold my strut mounts.
It was odd to find them there...but they work much better, do not come loose and were available from the dealer.
The stock spring washer works well but must be replaced at every gasket change. The heat takes the spring tension out of them. Ray |
I think this is the likely issue here. I'm 99% sure I reused the spring washers. For now I'll keep this on my list of things to do/check at every oil change.
_________________
1963 Ruby Red 356 Cabriolet
1976 Sage Green Westfalia Deluxe |
|
| Back to top |
|
|
tootype2crazy
Samba Member
Joined: October 08, 2007
Posts: 1276
Location: St. Louis Missouri
|
| Posted: Wed May 24, 2017 11:44 am Post subject: Re: PSA on vacuum leaks - check your intake manifold nuts! |
|
|
I've worked on hundreds of VWs in my time working at various ACVW shops and can tell you that all ACVW engines have the intake-stud-nut-loosening problem. Just as Ray said, the heat takes the 'spring' out of the wavy washers over time, although some are made better than others. My solution has always been to assemble with blue loctite in lieu of using expensive locking nuts. Works well, never saw one come loose on customer's cars.
_________________
air-cooled or nothing for me
1978 Sunroof Deluxe Bus (daily driver)
1978 Transporter (mom's, making into a camper)
1970 Single Cab 2.1 turbo/EFI 6 Rib, 78 front beam, vanagon backing plates on rear (project)
2001 GTI VR6 (wife's) |
|
| Back to top |
|
|
THall
Samba Member
Joined: August 25, 2010
Posts: 324
Location: Verona, WI
|
| Posted: Thu May 25, 2017 6:01 am Post subject: Re: PSA on vacuum leaks - check your intake manifold nuts! |
|
|
Decided to check mine last night after seeing this thread...sure enough, all eight were under 14 ft/lbs.
Torque check on these will certainly become part of routine maintenance.
_________________
'78 Westy - 2.0 FI |
|
| Back to top |
|
|
raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21511
Location: Oklahoma City
|
| Posted: Thu May 25, 2017 7:16 am Post subject: Re: PSA on vacuum leaks - check your intake manifold nuts! |
|
|
| tootype2crazy wrote: |
| I've worked on hundreds of VWs in my time working at various ACVW shops and can tell you that all ACVW engines have the intake-stud-nut-loosening problem. Just as Ray said, the heat takes the 'spring' out of the wavy washers over time, although some are made better than others. My solution has always been to assemble with blue loctite in lieu of using expensive locking nuts. Works well, never saw one come loose on customer's cars. |
Yes......I would consider this a chronic problem on the type 4 engine no matter which vehicle it came in. I had the same problem seemingly (to me anyway).....to a lesser extent on my type 3's.
I agree with the locktite. I would be careful to make sure the studs are securely in the heads to start with before using loctite.
One of the problems I did occasionally find with using actual locknuts.....and have found this on some engines I have stripped in the junkyards that were using schnoor type ribbed bellville lock washers in this spot......is that the torque value on these studs is pretty low.
It needs to be low to keep from cracking the phenolic spacer block. The use of some of the locknuts I have seen......like the Schnoor washers and distorted/dented locknuts......is that they can be over torqued just from the locking tension they impart to the stud.
I found far more cracked phenolic blocks from the use of Schnoor washers and from almost any type of lock nut other than the one I listed.
While that part # may or may not still be a live part #......I don't think that exact type of locking nut is still made the same way anymore.
I have been looking for some for a while and they are not made any more as far as I can tell. They are a very low tension lock nut.....or at least used to be.
Ray |
|
| Back to top |
|
|
airschooled
Air-Schooled
Joined: April 04, 2012
Posts: 12721
Location: on a bike ride somewhere
|
| Posted: Thu May 25, 2017 9:02 am Post subject: Re: PSA on vacuum leaks - check your intake manifold nuts! |
|
|
Do we know for certain if the nuts are backing off? Or is the loosening due to "settling in" of the block, two gaskets, sealant/grease/thin RTV, etc…
I hate those copper Type 1 exhaust nuts that are slightly out of round, but I bet someone has used them here.
Robbie
_________________
Learn how your vintage VW works. And why it doesn't!
One-on-one tech help for your Volkswagen:
www.airschooled.com |
|
| Back to top |
|
|
AB westy nut
Samba Member
Joined: June 01, 2010
Posts: 1124
Location: Calgary, Alberta
|
| Posted: Thu May 25, 2017 9:57 am Post subject: Re: PSA on vacuum leaks - check your intake manifold nuts! |
|
|
| asiab3 wrote: |
Do we know for certain if the nuts are backing off? Or is the loosening due to "settling in" of the block, two gaskets, sealant/grease/thin RTV, etc…
I hate those copper Type 1 exhaust nuts that are slightly out of round, but I bet someone has used them here.
Robbie |
That reminds me, I also checked the exhaust manifold nuts and all were good except one. So apparently even those oval copper nuts can loosen!
_________________
1963 Ruby Red 356 Cabriolet
1976 Sage Green Westfalia Deluxe |
|
| Back to top |
|
|
raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21511
Location: Oklahoma City
|
| Posted: Thu May 25, 2017 10:02 am Post subject: Re: PSA on vacuum leaks - check your intake manifold nuts! |
|
|
| asiab3 wrote: |
Do we know for certain if the nuts are backing off? Or is the loosening due to "settling in" of the block, two gaskets, sealant/grease/thin RTV, etc…
I hate those copper Type 1 exhaust nuts that are slightly out of round, but I bet someone has used them here.
Robbie |
Yes....they are backing off. While there is always "some" settling and it is part of the issue...and probably what causes the first "erg" of looseness....they actually back off.
I had the same question long ago and marked one with Sharpie.
The phenolic block will not outgas and permanently change shape....and phenolic has VERY low expansion/contraction. The factory gaskets are actually applied in the mold. They are thin and have very little squish. They are really there to seal the machine marks in the surface of the manifold and head and not to be full fledged "squishy" gaskets.
But....yes if you goop RTV on thick...really any thicker than a transparent smear....it will cause standard 8mm nuts to loosen pretty quick. Ray |
|
| Back to top |
|
|
Clatter
Samba Member
Joined: September 24, 2003
Posts: 7537
Location: Santa Cruz
|
| Posted: Thu May 25, 2017 10:02 am Post subject: Re: PSA on vacuum leaks - check your intake manifold nuts! |
|
|
Thanks for the PSA.
Appreciate you taking the time to post this!
Off to the garage to check intake manifold torque for camping trip...
_________________
Bus Motor Build
What’s That Noise?!? |
|
| Back to top |
|
|
THall
Samba Member
Joined: August 25, 2010
Posts: 324
Location: Verona, WI
|
| Posted: Thu May 25, 2017 10:14 am Post subject: Re: PSA on vacuum leaks - check your intake manifold nuts! |
|
|
| Quote: |
| That reminds me, I also checked the exhaust manifold nuts and all were good except one. So apparently even those oval copper nuts can loosen! |
Ha, I decided to check those as well after doing the manifold! Two were slightly under torque. And while I was at it checked all of the CV bolts...they were all good 
_________________
'78 Westy - 2.0 FI |
|
| Back to top |
|
|
williamM
Samba Member
Joined: August 07, 2008
Posts: 4333
Location: southwest Arizona
|
| Posted: Thu May 25, 2017 11:05 am Post subject: Re: PSA on vacuum leaks - check your intake manifold nuts! |
|
|
 great post- all I can add is those aggressive lock nuts can twist the stud when they tighten- that stud eventually "un twist it's self" causing the fastener to lose compression.
Then there is the well documented pinching of the fan tin where it dips down between the injectors.- this can leak right away or slip free of the manifold- causing yet another set of manifold nuts to lose their compression.
_________________
some days I get up and just sit and think. Some days I just sit.
opinion untempered by fact is ignorance.
Don't step in any! |
|
| Back to top |
|
|
raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21511
Location: Oklahoma City
|
| Posted: Thu May 25, 2017 3:22 pm Post subject: Re: PSA on vacuum leaks - check your intake manifold nuts! |
|
|
| williamM wrote: |
great post- all I can add is those aggressive lock nuts can twist the stud when they tighten- that stud eventually "un twist it's self" causing the fastener to lose compression.
Then there is the well documented pinching of the fan tin where it dips down between the injectors.- this can leak right away or slip free of the manifold- causing yet another set of manifold nuts to lose their compression. |
The real problem with "aggressive" locknuts....like. nylock....which I hate....and the diztirted/dented nuts.....is that if you are only shooting fof 14 ft. lbs.....some of them can take almost that much just to turn on the threads.
If it takes 5-7 foot pounds just to turn a threaded stud through a locknut.....your wrench will click when uou only have about another 7 ft lbs after contact with the solid surface of the manifold.
That's why I really liked the old screw tab style locknut. It had virtually no drag. It,worked by not letting the nut back off. It worked by reauiring more pressure to remove than install. Ray |
|
| Back to top |
|
|
StefansBus
Samba Member
Joined: November 20, 2015
Posts: 242
Location: Germany
|
| Posted: Fri May 26, 2017 12:33 am Post subject: Re: PSA on vacuum leaks - check your intake manifold nuts! |
|
|
Resurrecting an old topic here just to say that I had suspected an intake leak on my brand new 1600SP engine (due to lighter colored spark plugs on cylinders 3 and 4) and sure enough: The intake manifold nuts were lose
I recommend this check to anyone.
Stefan |
|
| Back to top |
|
|
airschooled
Air-Schooled
Joined: April 04, 2012
Posts: 12721
Location: on a bike ride somewhere
|
| Posted: Fri May 26, 2017 9:15 am Post subject: Re: PSA on vacuum leaks - check your intake manifold nuts! |
|
|
| StefansBus wrote: |
Resurrecting an old topic here just to say that I had suspected an intake leak on my brand new 1600SP engine (due to lighter colored spark plugs on cylinders 3 and 4) and sure enough: The intake manifold nuts were lose
I recommend this check to anyone.
|
Single-port engines have the neat little crush gasket between the manifold and the head; once you heat cycle the engine and it cools down, check the torque one more time and it should be good for the life of the engine.
Robbie
_________________
Learn how your vintage VW works. And why it doesn't!
One-on-one tech help for your Volkswagen:
www.airschooled.com |
|
| Back to top |
|
|
raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21511
Location: Oklahoma City
|
| Posted: Fri May 26, 2017 9:28 am Post subject: Re: PSA on vacuum leaks - check your intake manifold nuts! |
|
|
All of this being said....while looking for some of the old school tab locking nuts...I have come across a fantastic range of locking nuts that if you need them...show great promise.
Like these:
https://www.fastenright.com/general-fixings/aerotight-nuts/sl01
I have not contacted the company but I am betting since they are really aimed at aircraft...I would bet you could get them in a range of locking tensions.
The type 4 cars with 004 four speed use a split nut like this to lock the mainshaft into the case. The nut stays locked....is a 15mm hex....but designed to have about 18 flt lbs.
The closest thing I have found to the type of locknut I described in this thread (with the 113 part #)...is a DAX nut.
Like these. Notice the tabs around the rim. https://www.af1racing.com/store/Scripts/prodView.asp?idproduct=2528
And these are just gorgeous and are available with spring tension that can vary the drag on the threads for low torque locking
http://www.fastenerdata.co.uk/fasteners/nuts/prevailing-torque/vargal-nut.html
I think Fastenal can get the Vargal type spring nut. Ray |
|
| Back to top |
|
|
wcfvw69 
Samba Purist
Joined: June 10, 2004
Posts: 13389
Location: Arizona
|
| Posted: Fri May 26, 2017 4:58 pm Post subject: Re: PSA on vacuum leaks - check your intake manifold nuts! |
|
|
I can't imagine what these aviation nuts cost each
_________________
Contact me at [email protected]
Follow me on instagram @sparxwerksllc
Decades of VW and VW parts restoration experience.
The Samba member since 2004.
**Now rebuilding throttle bodies for VW's and Porsche's**
**Restored German Bosch distributors for sale or I can restore yours**
**Restored German Pierburg fuel pumps for sale or I can restore yours**
**Restored Porsche fuel pumps or I can restore yours**
**Restored Porsche distributors or I can restore yours** |
|
| Back to top |
|
|
|
