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75 Kombi 2.0 Engine revving high as it heats up.

Discussion in 'Engine & Transmission' started by Xombi75, May 12, 2022.

  1. Xombi75

    Xombi75 New Member

    Messages:
    28
    Location:
    Tweed Heads
    Hey folks ... i did a search and been reading posts all arvy. But couldn't find the exact same problem i'm having.

    Brand new 2.0 engine and gearbox and carbs - done about 2000kms. ...

    Coming home from mid north coast around kempsey, and the engine starts idling really high. feels like its at 3/4 throttle sitting at lights. Since i was on the hwy back and the engine temp was staying low and in 4th gear it just felt like having cruise control, i nursed her home at 90kms.

    Fast forward to now, back home and as soon as the engine warms up to running temp (around 60-70 degrees on the oil temp gauge) and she starts idling super high. in general she runs with lower power and pretty rough.

    I thought it was the accelerator cable but it seems fine, and still if it was, that doesn't explain the high idle as the engine warms up.

    Local mechanic said brake booster line could be leaking ... is that a chance?

    I've never heard of brake lines causing the engine to rev high. I would have thought maybe a vacuum line or something. It's hard bcos everything is brand new.

    Cheers if anyone has any ideas i can try!
     
  2. Mr Beckstar

    Mr Beckstar Well-Known Member

    Messages:
    1,225
    Location:
    Bateau Bay, NSW
    Just get the tuning and chokes checked.

    The brake booster is at the front of the bus and has a vacuum hose running from the inlet manifold at the rear. So yes it is a vacuum line rather than a brake line and it could cause high idle speed if it's leaking.

    But 3/4 throttle sitting at lights sounds a bit extreme for an air leak. Unless there are other things out of whack too.

    Perhaps your chokes aren't returning fully when the engine is warm. This could be supported by the rough running when warm. Check the wires are connected to the chokes! And if they are, are they getting voltage? Or perhaps the bimetal strip is broken??

    Perhaps your idle speed is set way too high. And maybe someone did that because the chokes aren't coming on properly so it stalls when it's cold. The point I'm making there is it needs to be checked before you'll know what's causing it because there are plenty of possibilities.

    Needs idle speed/mixture, chokes and dwell/advance checked from scratch in my opinion. Otherwise you could be chasing your tail. First step in that process is check for vacuum leaks and fix.
     
    Last edited: May 12, 2022
    oldman, Wayne murray and Xombi75 like this.
  3. tintop

    tintop Well-Known Member

    Messages:
    1,078
    Location:
    Canberra
    mmm yeah he means the vacuum line that goes to the brake booster

    I'd be looking to see if the the throttle valves are returning to (nearly) closed position ... perhaps your chokes aren't adjusted correctly (or the wires are off) - which would increase the idle and make it run rough
     
  4. Xombi75

    Xombi75 New Member

    Messages:
    28
    Location:
    Tweed Heads
    thanks peeps.

    It's dual carbie ... will those choke wires run to the positive on the starter, or the battery?
     
  5. Xombi75

    Xombi75 New Member

    Messages:
    28
    Location:
    Tweed Heads
    Also if anyone knows a good VW mechanic on the goldie area, i'd love to know about them.

    i don't mind driving for a good one, if one is a bit further abroad.
     
  6. Mr Beckstar

    Mr Beckstar Well-Known Member

    Messages:
    1,225
    Location:
    Bateau Bay, NSW
    The positive wire on your coil that comes from your ignition switch is normally looped to the two carb chokes.
     
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  7. oldman

    oldman Super Moderator Staff Member

    Messages:
    11,311
    Location:
    Avalon Beach NSW
    Welcome to KC !
    x2 for a vacuum leak…
    Worth a check of the one way valve in brake booster hose from the inlet manifold takeoff.
    Could also be a failed diaphragm within the booster itself….how do the brakes feel ?
    If it’s that new….take it back to whomever did the build and ask them to check it….surely it’s still under warranty?
    Good luck.
    Cheers,
    Mark
     
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  8. Xombi75

    Xombi75 New Member

    Messages:
    28
    Location:
    Tweed Heads

    Thanks so much mate!

    the brakes feel fine, which is why i was wondering about the whole booster hose thing. i thought the mechanic was meaning the vac hose bcos i wasn't sure how the booster could affect the idle/ revs. but obviously there is a hose between the two that isn't the vac line?



    Ahhh, i cant. it's a penrose 2.0 engine & 6-rib gearbox but the guy who put it together is in torquay, vic. And i'm on the tweed coast. so taking it back is not possible.

    I haven't owned a kombi in 20 yrs, so my knowledge is rusty. slowly coming back, but it's rusty. lol
     
  9. oldman

    oldman Super Moderator Staff Member

    Messages:
    11,311
    Location:
    Avalon Beach NSW
    Yup,as Chris posted….. brake booster is vacuum activated via a hose connecting the booster to the inlet manifold via a vacuum hose. There is only one hose for this purpose.
    There is a one way valve (inline and close to the manifold) that maintains the vacuum. It’s easy enough to check. Remove it and see if it only operates in one direction. There is an arrow that should point in the direction of the booster.
    Any breech of a vacuum line anywhere will cause increased revvs.
    There are also a number of other vacuum lines in the engine bay that can fail……run the engine and check for an audible hiss……
    Is your Penrose engine running Cadence carbs. ? They can be problematic and could be the issue……
    Check all the linkages and carb. return springs too…….
    Bugger about the warranty.
    Cheers,
    Mark
     
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  10. Xombi75

    Xombi75 New Member

    Messages:
    28
    Location:
    Tweed Heads
    yep, no audible hissing, brakes were working fine. strong peddle, not spongy and pulling me up on a dime. return springs seemed to be all brand new, not stretched or tired and all in their seats.

    I'm pretty sure they're dual weber carbs; but they're defs with the crossbar linkage...
     
  11. oldman

    oldman Super Moderator Staff Member

    Messages:
    11,311
    Location:
    Avalon Beach NSW
    Penrose was fitting “Cadence” carbs. to his engines as an option.
    They are a Weber knock off made in China and have been known to give folks issues.....
    Maybe the issues with them have been sorted out by now.....I first saw them at the Nationals years ago.
    If yours are true Webers, they’ll be branded as such.
    Cheers,
    Mark
     
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  12. Barry

    Barry Well-Known Member

    Messages:
    6,503
    Location:
    Abbotsford NSW
    Do you mean a Wayne Penrose or a Rod Penrose?

    Is it a type 1 or 4?

    Rod doesn't (normally) do Type 4
     
  13. Xombi75

    Xombi75 New Member

    Messages:
    28
    Location:
    Tweed Heads
    The engine was from Rod, but all the parts like coil, carbies, cables, alt etc etc were fitted by the guy I bought it off. The 6-rib was from denhams who do all of rod's gearboxes.

    the engine and gearbox are so rock solid ... i'm having some problems with all the accessories old mate fitted himself. lol
     
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  14. Xombi75

    Xombi75 New Member

    Messages:
    28
    Location:
    Tweed Heads

    Cheers Mark. The bus is in the shop getting the hose lines looked at and a RWC done.

    When i get her back i'll verify, but i'm positive they're webers!
     
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  15. Xombi75

    Xombi75 New Member

    Messages:
    28
    Location:
    Tweed Heads
    Got Jenny back ...

    vac lines and accelerator cables were all fine. The webers weren't in sync. So the mechanic tuned them. She's still running really, really rough. she's just not idling through the roof anymore.

    The old guy i got it off also had chrome rocker covers *insert eyeroll* (i have the originals) and they're leaking oil and possibly the valves don't have enough clearance under the non standard covers ... so valves are popping when i back off the accelerator. fingers crossed it's not burned valves. but given the way the guy has finished off all the engine and bus in general, i wouldn't be surprised!

    gonna take her up to a kombi mechanic in mermaid beach next friday. hopefully he can fix her up and it's not all worst case scenarios. lol.


    Still, got some steering arm leak, and the rocker cover leaks to be fixed to get a RWC.
     
  16. Wiz

    Wiz Well-Known Member

    Messages:
    681
    Location:
    Near Ballarat
    In the middle of the beam where the swing lever pivots?
    PR
     
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  17. Wayne murray

    Wayne murray Well-Known Member

    Messages:
    4,900
    Location:
    Seven hills
    Did the mechanic make all four chambers in sync with each other and did the mechanic also makes sure that both carburettors are working at the same time.
    So you want each chamber equal with each other. Sucking the same amount of air.Two chambers per carburettor.
    Also as you put your foot down on the accelerator, are the two carburettors coming on( working) at the same time , equal to each other. As if one carburettor is working before the other , it makes the car feel like it’s shaking, as one side of your engine is working better then the other.
    If the webers are from Rod I’ll take it they may be Spanish carburettors.It may have on the carburettors that they are made in Spain.
    I have a set and have also heard a lot of people that have had the Spanish webers there is an issue with the idle circuit.
    As you turn out your idle jet screw to adjust it, what is also happening is the brass seat the jet seats into moves at the same time as each other. Until the brass seat stops moving at a specific spot, which allows more air to be sucked around the seat. If it is this the brass seats moving they need to come out and the brass seats, locitite back in place.
    It is most likely easier to have carburettors off the car to do this.
     
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  18. oldman

    oldman Super Moderator Staff Member

    Messages:
    11,311
    Location:
    Avalon Beach NSW
    Sounds like it really needs a VW mechanic to go over it and set it up properly as a baseline, rather than a mechanic......;)
    They are worlds apart.
    Valves need to be set stone cold, then points, timing and carbs. adjusted, balanced/synched.
    Your description of "popping" sounds like the timing is out...rocker covers would not affect the valve clearances....if the covers were so tight that the rocker bolts were hitting them, it'd sound like a Gattling gun !!
    You'll get there...just get a proper mechanic experienced with VW / air-cooled.
    Cheers,
    Mark
     
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  19. Xombi75

    Xombi75 New Member

    Messages:
    28
    Location:
    Tweed Heads
    there's that single bolt in the middle. it's dripping off that?
     
  20. Xombi75

    Xombi75 New Member

    Messages:
    28
    Location:
    Tweed Heads

    yeah exactly ... i only went to the local mechanic bcos he's a good honest fella and 2 minutes away, and thought he'd get it running better than i could. it's all booked for next friday for the VW mechanic to go right over it. I can't wait.

    i was starting to think on the drive home, the popping could almost be the gasket from the manifold to the carb (or both) sucking air?

    how good are kombi's! my problem solving skills are already so much sharper than they have been in 20 years. ironically that was the last time i owned a kombi haha
     

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