Throttle shaft vacuum leak - stuck on the road somewhere

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asiab3
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Throttle shaft vacuum leak - stuck on the road somewhere

Post by asiab3 » Wed May 14, 2014 12:58 am

Hi all, I'm 300 miles into a 2,000 mile round trip, and I'm a bit at a loss of what to do with this brand new leak. CHT readings began to grow today, from my usual cruise around 360 to a cruise at 380 as the ambient temperatures dropped. At a gas station I sprayed the usual suspects and found this:

http://www.youtube.com/watch?v=wJzi8tjUqa0

I'd really like to get back to my worry-free "kickback and floor it up the hill" attitude. I also don't want to drive 1,700 miles with this leak.

What ideas do we have to get this minimized and get back on the road?

Thanks,
Robbie

Ps- throttle positioner is disconnected and capped (red) for troubleshooting only. It's usually connected and functions perfectly.
1969 bus, "Buddy."
145k miles with me.
322k miles on Earth.

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Re: Throttle shaft vacuum leak - stuck on the road somewhere

Post by Amskeptic » Wed May 14, 2014 6:22 am

asiab3 wrote:Hi all, I'm 300 miles into a 2,000 mile round trip, and I'm a bit at a loss of what to do with this brand new leak. CHT readings began to grow today, from my usual cruise around 360 to a cruise at 380 as the ambient temperatures dropped.
What ideas do we have to get this minimized and get back on the road?
Don't even worry about it. You have plenty of compensating ability with your mixture screw. I am curious why the idle dropped when you sprayed. I run lean enough that the idle actually goes up when I spray at leak points . . .
Colin

(p.s. snug the carburetor nuts a tad)
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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Re: Throttle shaft vacuum leak - stuck on the road somewhere

Post by asiab3 » Wed May 14, 2014 6:48 am

Does the mixture screw affect partial throttle cruising?

I may have already messed with the mixture screw before the video. Or I might have after- I don't remember it was late and I was angry. :scratch:
1969 bus, "Buddy."
145k miles with me.
322k miles on Earth.

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Re: Throttle shaft vacuum leak - stuck on the road somewhere

Post by Amskeptic » Wed May 14, 2014 6:08 pm

asiab3 wrote:Does the mixture screw affect partial throttle cruising?

I may have already messed with the mixture screw before the video. Or I might have after- I don't remember it was late and I was angry. :scratch:
Yes. Play. Experiment. Also, if you have a bypass carburetor (big brass screw) you may find very good things in driveability if you crank that sucker open as far as you can within the upper limit of decent idle rpm. I have even reduced timing in the name of good air flow through the carburetor at idle. It smooths the transition to main circuit and gives your mixture screw a bit more range.
Play in bold strokes. See if radical leaning helps, and go rich in 1/4 turn increments over a coupe of hundred miles. Be aware too of your other variables. I was about to get ham-handed in the AFM because my CHTs were inexplicably 380* yesterday, why? Well . . . the winds had changed.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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Re: Throttle shaft vacuum leak - stuck on the road somewhere

Post by asiab3 » Fri May 16, 2014 4:16 pm

Amskeptic wrote:
asiab3 wrote:Does the mixture screw affect partial throttle cruising?

I may have already messed with the mixture screw before the video. Or I might have after- I don't remember it was late and I was angry. :scratch:
Yes. Play. Experiment.

Play in bold strokes. See if radical leaning helps, and go rich in 1/4 turn increments over a coupe of hundred miles. Be aware too of your other variables. I was about to get ham-handed in the AFM because my CHTs were inexplicably 380* yesterday, why? Well . . . the winds had changed.
Colin
It's 103* here, I was hoping the bus would handle the heat better than I can…

The winds were still yesterday, 380* cruise consistently. Today's headwinds brought a 390 cruise with gusts pushing us up to 400*. I drove this same route a month ago with an enormous headwind and temps rarely got above 380* floored into the wind.

This episode started last week.
28*btdc hoses off, 34pict3, 127.5 main, 60 air, stock exhaust.

The bus was running like a top and my girlfriend and I decided to take a trip from San Diego - Phoenix - Monument Valley. Heading for Phoenix, I was pulling a slight hill and saw CHTs rise rapidly past 400* and head a slight bit of pinging out the drivers window. I hadn't seen a temp over 390* in a month, except for a full throttle run up the Grapevine and Indio Grade in the heat of the day.

This lead me to check for leaks, and that's when I posted this thread. Quarter turns of the mixture screw made very little difference at cruise, but made a difference in temps at idle. Idle volume/speed screw adjustments made a temp difference at idle, which I think were cooling fan speed related.

I also made some major timing changes along long, hot, and flat freeway runs. About 25-50 miles each change - all hose off for timing.
28* - what I started with - pinging in San Diego
25* - got freeway temps into the "get there but don't push it" range
22* - same cruise temps, but apron was dang hot and oil temp/pressure didn't like this at all.

Set it back to 25*, made it to Phoenix, and had to cancel my first ever trip on account of the bus. :pale:

I've set it to 28* again in Phoenix, and temps haven't changed on any 10 mile freeway runs that I've been doing in the mean time.

I have three more days to get back to San Diego, and I'd like to be able watch the mountains instead of the dashboard.

Apologies if this sounds like thought-vomit. I will be checking my valves for changes when the engine cools off, and I'm trying to find a friend in Phoenix with a known good 34pict3 to swap in and compare.

Robbie
1969 bus, "Buddy."
145k miles with me.
322k miles on Earth.

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Re: Throttle shaft vacuum leak - stuck on the road somewhere

Post by Amskeptic » Fri May 16, 2014 9:52 pm

asiab3 wrote: Apologies if this sounds like thought-vomit.
Oh me too. Here's mine.

Will you R-E-L-A-X already?? Do you know how many people's lives have been turned upside down by becoming slaves to a stupid gauge, obsessing over every stupid little hill or breeze?

ONE HUNDRED THREE degrees, did you say? How the hell is the engine supposed to be running as cool as you like when the cooling air itself is hot?

How do you suppose Volkswagen managed to sell these cars all around the world for people without any gauges? These cars can TAKE IT. All of the whining and mewling about how these cars can't handle this and can't handle that (look at those horrible advertisements for all that aftermarket junk) is in most every single case that I have run across because of some human error. They sure as shit were not as conscientious as you are. They were nowhere near as alert as you are. And YOU are the guy changing his plans because of some stupid gauge number? You need to read some of my desert trips. Why the hell do I do them endlessly, but to prove that these cars can take it? I add more thousands of highway miles AFTER I broil the damn thing just to make sure that I didn't "weaken it" like some would claim. Read about the 460* head temps in the Road Warrior where I was laughing at and cursing the VDO CHT gauge that RandyInMaine had lent me. I knew my engine better than some stupid interloper leering at me from the dash, I laughed and did not let up the accelerator one damn bit. That was what, 2005 6 7? Can't remember but that the heads gave me 515,000 miles before they were ruined by a machine shop, go figure.

So try this: Jake Raby passes out cold at the thought of a Type 4 engine running CHTs above 400. He says that the seats will fall right out. So he suggests Len Hoffman heads. You pay for proprietary seat installation techniques that are guaranteed to keep the heads happy. My question is, if the Len Hoffman seat installation technique is that magnificent, can they handle a little more heat? I trust these used Yuma heads in Chloe, I trust the BobD original heads implicitly! Implicitly and explicitly! Take me to the hottest damn place on Earth and give me the hottest damn day it can offer up, and let me drive one more damn time from 238 feet below sea level to the Towne Pass at 6,000 feet at full throttle for 28 miles, and this time will you please read the write ups?

p.s. if it is hot outside your engine will be hot! that is not abnormal.

***************************************************************************

by Amskeptic » Fri Aug 03, 2007 7:05 pm

Just a quickie, this Starbucks has a busted air conditioner and they are closing it.

Just did the Las Vegas to Barstow run. It is 117* outside. My dad is a trouper but this heat is getting to him.

Engine did fine, oil 245* case at lower left 220* (air flow) exhaust pipes at about 765* taco plate 240* it is hot but running well. Did some truck drafting hopscotch up the hill, works good. So disappointed that this Starbucks had no a/c. . . .

Out into the frying pan. . .
Colin

**************************************************************************************

July 20, 2008

Now it is 100 degrees as I head east on CA168? to Nevada where I pick up US95 once more. And it was 102* on the long stretches up hill where the headwind began to make my little bus work too hard. The temperatures were startling:
Exhaust pipes L 822* R 812*
Oil filter 254*
Crankcase left rear corner 242*
Left valve cover 282* (ouch!)
Right valve cover 242*
Muffler 654* at center
Pavement 134* in the sun

**************************************************************************************
July 19, 2009
There is no describing it, but I am glad I got to enjoy it from the vantage point of an old air-cooled VW where the waves of stunning heat are not just something to see from the glass-enclosed A/C aquariums that passed me, noooooo . . . this heat is talking directly to me and it is talking to my poor engine and it is definitely harrassing my fuel pump, and that Makes The Day, the sheer unbelievability of this deadly heat concentrates you beautifully, the shared passage where you are praying to your exhaust valves to carry you through, the understanding that this big old planet in the Universe rotates around a furnace and you can feel it like you never have, Today:

May 16, 2014
See, "praying to your exhaust valves". If YOU want to know what YOUR engine thinks, get out there and drive it! THEN go ask the valves what they thought. Did you clearances close up? If they didn't, there it is, your Free Get Out Of Gauge Hell card. You did read, I presume, that the BobD swallowed a plastic bag three and a half weeks ago and my head temps went up to 535*. My valve adjustments showed not a trace of upset. Gauges are good for that sort of emergency. I am still driving it.

You know that the exhaust valves run at a red hot 1,000* on their faces, right? Intakes run at about 300-400*. It is not so much the heat itself that you need to collapse in terror over, it is the differential across a lousy 1/2" of suffering aluminum. Have you wondered why these engines block the damn cooling air right across the center of the cylinders and heads? Because the intakes are too cool. Too cool! Heat them up a bit, give the cooling air to the exhaust sides of the heads and the outside of the cylinders because it ain't the heat itself that causes all these cracks, it is the temperature differential. I'll take a hot damn desert any day over a cold 45* day on a long uphill with a lean running engine.

Chloe (singleport 1600) did < DID get pissed off with me when I ran 2,000 miles at freeway speeds with head temps that would stay in the 420-430 range until I discovered that it had too-small fuel injection exhaust valves running on their outside rims. The seats, though damaged by extreme gas cutting shrouding, were firmly in the heads and the valves were fully within spec.

Ask yourself if these engines can't take a lousy 410* up a hill every once in a while. Now give yourself 420* just for the hell of it. My gauge blinks at 430*. I'm still here, still driving without a care . . . except for trashy plastic bags.
Colin

Image

(p.s. now that I told you to relax, what is with this pinging? Do you have atrocious carbon build-up in your combustion chambers? High compression? Only under load?)
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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Re: Throttle shaft vacuum leak - stuck on the road somewhere

Post by asiab3 » Fri May 16, 2014 11:54 pm

I long for an engine that I can trust- fact is I don't trust it right now. I was about to… It was so damn consistent and happy.

Pinging- months of trouble-free travels all over the state, then one measly hill rattles our bones with NO changes to the engine. I sprayed water down the intake while keeping it revved up, and it has not come back since.

Temps- Last month, full throttle runs all over the steepest grades I could find. Something like 22 minutes to climb Indio (5%, 4th gear held at 50mph,) full throttle around 90* outside and I barely hit 405*. The numbers do not bother me as much as the shift in trends. Now I run at partial throttle on the freeway at 50mph and the flat ground temps hover in that range. A slight grade pushes me to 420*, and a full throttle run gets to 440* without trying.

Oil does not smell burnt. Is that a safer reading than a pressure gauge, even if it shows pressure is less than 10psi per thousand rpm?

Thoughts on disconnecting the gauges for the drive back? I want to trust this engine, I really do.

Sent from my phone to keep the thought-vomit to a minimum.
1969 bus, "Buddy."
145k miles with me.
322k miles on Earth.

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Re: Throttle shaft vacuum leak - stuck on the road somewhere

Post by Amskeptic » Sat May 17, 2014 8:09 am

asiab3 wrote: Last month, full throttle 90* outside barely hit 405*.
Now full throttle run gets to 440* without trying.

Oil does not smell burnt. Is that a safer reading than a pressure gauge, even if it shows pressure is less than 10psi per thousand rpm?
After my marvelous ode to heat . . . you write the above numbers?
I should have seen that little 440* nugget in your prior post (that would have saved everyone from my torrent of words).

440* is not good. Pinging is not good. Now go investigate. You may have read where I botched Chloe's happy spot with a line of cars behind me in a one-lane-only interstate construction zone. All I did was play with the timing and mixture a little, and all hell broke loose. I was so sad. Like you, I was about to trust.
In my case, I discovered that the flap cross shaft had disassembled itself, and I had to "look" for fallen little push-on retainers with burned fingertips. After reassembling those infernal little things, the temps got worse still. That is when I discovered that the thermostat rod was binding just a 1/4" before fully open. The engine was actually cooler with the disassembled cross shaft, because the left side was at least able to open fully.

As you consider what changes might/must have occurred, use forensic analysis, i.e. separate into "acute" or "chronic" onset (did these higher temperatures show up suddenly or did they creep up?), recall any variables however slight, and consider the dumb irritants of life (did a piece of crap block the main jet or did a bit of gasket lint suck into the power drilling? Look at the parts of the engine that will tell you their story (do you now have bleached spark plugs?).

The cause awaits your discovery.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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Re: Throttle shaft vacuum leak - stuck on the road somewhere

Post by asiab3 » Sat May 17, 2014 3:37 pm

I will be the first to admit- I would like to speak with my engine, but I don't know how to interpret what the plugs want to say.

4 and 3 look consistent, but 1 and 2 look like they have some sort of growth or deposit.

Image


I disassembled the carb and removed and blew GumOut through the main and air jets. I blew it through the power nozzles too, and all orifices seemed clear. Removed and inspected the DP boots and they were solid and snug. Both sides of the flaps are 100% open. Belt seems looser when cold but deflects correctly when warm; no glazing.

I am leaning towards a cooling issue, not intake, based on the following evidence:

Earlier this year when I saw a rise in overall temps, I had an intake leak at the left DP boot. Onset was slow and appeared gradually- first starting to heat up under load, graduating to high cruising as well. Retarding the timing lowered the temps enough to take the interstate a few hundred miles home. Oil pressure was still 12psi per 1k RPMs warmed up, which it has been since I started monitoring it two years ago. CHTs dropped considerably with a downshift up a grade, or letting off the accelerator down a hill or offramp. Fuel economy was between 22 and 26 mpg, way too high.

Now, my oil pressure is struggling to keep to 10psi/1k rpm at warmed up cruise, changing timing or mixture screw doesn't change the temp trends, and CHTs do not drop NEARLY as much when coasting or downshifting. CHTs climb at idle and they never have before. Fuel economy is between 18 and 21. This was an extremely acute/sudden onset. One day perfect, the next day pinging.

I have been fortunate to find easy fixes with this bus so far; this new forensic diagnostic path is pushing me to my limits, but I hope soon to have a better understanding of the systems involved. I thank you for your patience, and I will do my best to more accurately describe symptoms and results.
1969 bus, "Buddy."
145k miles with me.
322k miles on Earth.

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Re: Throttle shaft vacuum leak - stuck on the road somewhere

Post by Amskeptic » Mon May 19, 2014 7:16 am

asiab3 wrote:
I would like to speak with my engine, but I don't know how to interpret what the plugs want to say.
4 and 3 look consistent, but 1 and 2 look like they have some sort of growth or deposit.

I am leaning towards a cooling issue, this was an extremely acute/sudden onset.
Good morning,
I got a cup of fierce coffee here.
#3 plug has the no-no "white powder" around the perimeter. You are running too lean. Best that you check your valve clearances and compression again, to make sure the essential architecture is still solid.

On a cold engine, make the mixture a known lean with the mixture screw (just turn it in until the idle drops a tiny bit).
Get your favorite volatile aerosol compound (that does not strip paint if you have pretty tins), and spray the intake manifold-to-cylinder head area. Does the idle go up?

If yes, replace intake manifold gaskets. See if yours have a mangled look at the locating dowel.

Also, #3 spark plug shell on the outside surface has a little burn/scorch area. Is your ring terminal allowing blowby? I do *not* take off the spark plug gasket, I just put the ring terminal over it.

If you find no evidence of vacuum leak or incorrect fuel level or low fuel pump output, have you checked the fan for any obstruction? Want to waste a day pulling the engine and removing the fan housing, cleaning oil cooler, etc?
I gots the thread for that one . . .

viewtopic.php?f=65&t=10233#p182573

June 28th, our appointment day, we are supposed to be doing involved chassis stuff like ball joint boots and transaxle side seals. Don't think I won't go straight to the engine . . . :blackeye:
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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Re: Throttle shaft vacuum leak - stuck on the road somewhere

Post by asiab3 » Tue May 20, 2014 4:10 pm

Back safe in San Diego. Hot but uneventful drive. I wish I had some findings to report.
Amskeptic wrote: #3 plug has the no-no "white powder" around the perimeter. You are running too lean. Best that you check your valve clearances and compression again, to make sure the essential architecture is still solid.

Also, #3 spark plug shell on the outside surface has a little burn/scorch area. Is your ring terminal allowing blowby? I do *not* take off the spark plug gasket, I just put the ring terminal over it.
Valves/compression did not change a thousandth over the 1,100 mile trip. According to my notes, valves have not tightened in almost 5k miles, and even that was only one hour (of a turn) on #3 exhaust. A few have loosened over that time, but that's just adjuster wear, RIGHT?

I kept a metaphorical eggshell in between my foot and accelerator pedal, and that seemed to keep the cruise temp around 400. Grades went to 430 until I said "ohkaaaay" and downshifted. Would have EASILY kept going higher. Power was not the issue, just temps.

The blowby on the #3 shell is from a few months ago when you helped me diagnose the off-center sender issue because I had it bent wrong. I added the crush washer after this picture, and temps did not change.
On a cold engine, make the mixture a known lean with the mixture screw (just turn it in until the idle drops a tiny bit).
Get your favorite volatile aerosol compound (that does not strip paint if you have pretty tins), and spray the intake manifold-to-cylinder head area. Does the idle go up?
If yes, replace intake manifold gaskets. See if yours have a mangled look at the locating dowel.
Half a can of GumOut later, there is no RPM change at the base of the outer manifold/head connection. I have the metal gaskets in there now, the paper type made a mess last time I took the manifolds off, do you have a preference?

The builder "removed" the locating dowels on both heads. What do they do, exactly? My thought was the studs themselves do the locating.
If you find no evidence of vacuum leak or incorrect fuel level or low fuel pump output, have you checked the fan for any obstruction? Want to waste a day pulling the engine and removing the fan housing, cleaning oil cooler, etc?
This sounds like a lovely day. Playing an opera this weekend, and next weekend I will have my engine out. A greater hobby dichotomy I challenge you to find. :compress:
June 28th, our appointment day, we are supposed to be doing involved chassis stuff like ball joint boots and transaxle side seals. Don't think I won't go straight to the engine . . . :blackeye:
Colin
I recently found your output shaft seal procedure. I shall attempt that soon to free up engine time for us. Win-win, no? (PS- I found the deep seals you mentioned, is it worth hunting for the shallow ones?)

Robbie
1969 bus, "Buddy."
145k miles with me.
322k miles on Earth.

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Re: Throttle shaft vacuum leak - stuck on the road somewhere

Post by Amskeptic » Thu May 22, 2014 8:18 am

asiab3 wrote: no RPM change at the base of the outer manifold/head connection. I have the metal gaskets in there now, the paper type made a mess last time I took the manifolds off, do you have a preference?
The builder "removed" the locating dowels on both heads. What do they do, exactly? My thought was the studs themselves do the locating.
The dowels divide the expansion/contraction from the center on out only.
asiab3 wrote:
Want to waste a day pulling the engine and removing the fan housing, cleaning oil cooler, etc?
This sounds like a lovely day. Playing an opera this weekend, and next weekend I will have my engine out. A greater hobby dichotomy I challenge you to find. :compress:
My uncle would race Formula One for Ferrari, then take in Giuseppi Di Stafano and Maria Callas belting out Lucia di Lammermoor at La Scala. He would have gotten you.
asiab3 wrote: I recently found your output shaft seal procedure. I shall attempt that soon to free up engine time for us. Win-win, no? (PS- I found the deep seals you mentioned, is it worth hunting for the shallow ones?)
Robbie
Do a good solid job on the deep seals and that will be the last time. I have no idea how they are going to come out on Chloe should I need to replace them.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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