• From: Green Bay, WI
  • Registered: 2007-05-25
  • Posts: 62

Topic: Ashy Heat Riser Tube...what could cause this??

I installed a new intake manifold last fall because one of the heat riser tubes had developed a hole and needed to be replaced.  After a few times driving it developed a white ashy look to the left side and was very hot to the touch after just a minute or so to pull it out of the garage and back in.  I posted a video on youtube to show what it looks like http://www.youtube.com/watch?v=gqewHP5FZl4  any suggestions to help fix this problem so I don't develop another hole would be greatly appreciated.

Greg
1600cc '62 Beetle Sedan (Betty)

Teaching is the profession that teaches all the other professions.  ~Author Unknown
  • From: Cincinnati, Ohio
  • Registered: 2005-09-10
  • Posts: 2,318

Re: Ashy Heat Riser Tube...what could cause this??

RedHawker10 wrote:

I installed a new intake manifold last fall because one of the heat riser tubes had developed a hole and needed to be replaced.  After a few times driving it developed a white ashy look to the left side and was very hot to the touch after just a minute or so to pull it out of the garage and back in.  I posted a video on youtube to show what it looks like http://www.youtube.com/watch?v=gqewHP5FZl4  any suggestions to help fix this problem so I don't develop another hole would be greatly appreciated.

First let me say great job with the You-Tube video!!! smile  Info like that REALLY helps when discussing via the internet.

My best guess's are that the "ashy" appearance & extreme heat on the left side riser is due to:

- Maybe that riser has somehow gotten blocked.  Seems unlikely since you just installed it last Fall...it would probably depend how many miles you have put on it.

- One or both of the cylinders on the left side of the engine (facing the engine) are running hot.  Maybe the valves need adjusting, and maybe check the spark plugs as well.  Pull all 4 spark plugs (don't mix them up) and compare them with each other to see what they look like (ashy vs. black).  This should help you determine if one or both cylinders on the left side are contributing to the problem.

That ashy appearance on that left heat riser is definitely the black paint burning off due to the increased temperature.

Again...great job including the video! smile

- Nick

1979 Super Beetle Convertible
  • From: Austin, TX USA
  • Registered: 2004-03-30
  • Posts: 240

Re: Ashy Heat Riser Tube...what could cause this??

Greg,

In the video, it looks like there's some engine tin missing on both sides of the engine. I don't know if this is a temporary removal as you were working on the engine, but of you're driving it like that, the engine will definitely run hot and could be the culprit. Just going after the easy stuff first... :-)

Thanks,
-David

  • Registered: 2009-06-25
  • Posts: 554

Re: Ashy Heat Riser Tube...what could cause this??

The left side being hotter is normal, the exhaust flows from the left side to the right side. Like Nick said, the ashy appearance is the surface coating burning off. It happens on aftermarket tubes, and on mine the plating actually burned off of the left side.

And, like David mentioned, that engine tin needs to be installed for proper cooling. If any parts are missing, then the engine will keep recirculating the hot waste air from underneath the engine.

  • From: B.C.Canada
  • Registered: 2005-01-26
  • Posts: 2,586

Re: Ashy Heat Riser Tube...what could cause this??

Altema wrote:

The left side being hotter is normal, the exhaust flows from the left side to the right side. Like Nick said, the ashy appearance is the surface coating burning off. It happens on aftermarket tubes, and on mine the plating actually burned off of the left side.

In my '71 Super it flows right to left. It is connected to the exhaust manifold on the right where there is pressure and it's connected on the left, inside the pea shooter, where there is a partial vacuum. The depth of the left pea shooter is critical to the flow rate. Could yours be wrong?

jim

'71 SB(DD only 79K(now 84K miles) & '78 FI Westy (project)
PO of '65 Beetle in '69, '70 Crewcab & '70 Ghia in '77
'71 Super inside rear vents now available
http://www.openroad.ca/volkswebbin/view … p?id=85915
  • From: Green Bay, WI
  • Registered: 2007-05-25
  • Posts: 62

Re: Ashy Heat Riser Tube...what could cause this??

Hey guys thanks for the ideas, I did remove the tin just to get easy access to the two bolts that connect the heat riser tubes to the exhaust.  The aftermarket manifold did not match up completely and I was only able to get one bolt in on each side.  It makes the engine sound a bit louder than it should.  I haven't adjusted the valves in a while so hopefully that will help a little.

James, what do you mean by pea shooter?

Thanks for the kudos on the video...I'm a visual person so I figured it would be the best way to show you guys whats going on.

Greg
1600cc '62 Beetle Sedan (Betty)

Teaching is the profession that teaches all the other professions.  ~Author Unknown
  • Registered: 2009-06-25
  • Posts: 554

Re: Ashy Heat Riser Tube...what could cause this??

jamesdagg wrote:
Altema wrote:

The left side being hotter is normal, the exhaust flows from the left side to the right side. Like Nick said, the ashy appearance is the surface coating burning off. It happens on aftermarket tubes, and on mine the plating actually burned off of the left side.

In my '71 Super it flows right to left. It is connected to the exhaust manifold on the right where there is pressure and it's connected on the left, inside the pea shooter, where there is a partial vacuum. The depth of the left pea shooter is critical to the flow rate. Could yours be wrong?

jim

If that is looking at the engine from the back of the car, then they probably changed the flow direction in later years. Mine is the opposite of yours, but the same as the OP's bug. The left side being hot is an extra problem in the Ghia's because they moved the battery to the left side in 69 I think, and when that riser starts leaking it shoots exhaust at the battery.

Paul

  • From: B.C.Canada
  • Registered: 2005-01-26
  • Posts: 2,586

Re: Ashy Heat Riser Tube...what could cause this??

Pea shooters are the two chrome tail pipes that stick out of the muffler at the rear.

On '70 to '73 engines you insert a tape measure into the center of the left tail pipe until it contacts the preheating pipe inside the muffler. Then slide the tail pipe in or out to the proper spec which depends on the length of pipe you have. They come in 3 different lengths. Adjust the right pipe to match.

'74 engines both project 155 mm from the muffler. This measurement is critical to create the right pressure drop and flow rate.

jim

'71 SB(DD only 79K(now 84K miles) & '78 FI Westy (project)
PO of '65 Beetle in '69, '70 Crewcab & '70 Ghia in '77
'71 Super inside rear vents now available
http://www.openroad.ca/volkswebbin/view … p?id=85915
  • Registered: 2009-06-25
  • Posts: 554

Re: Ashy Heat Riser Tube...what could cause this??

jamesdagg wrote:

Pea shooters are the two chrome tail pipes that stick out of the muffler at the rear.

On '70 to '73 engines you insert a tape measure into the center of the left tail pipe until it contacts the preheating pipe inside the muffler. Then slide the tail pipe in or out to the proper spec which depends on the length of pipe you have. They come in 3 different lengths. Adjust the right pipe to match.

'74 engines both project 155 mm from the muffler. This measurement is critical to create the right pressure drop and flow rate.

jim

By "wrong", I thought you were referring to flow direction, not the exhaust tip inset. My bad.  I'll have to check mine, as I just matched the length of the aftermarket pipes with the original peashooters. Of course, I doubt my current pipes have the same flow characteristics, so it may be a moot point.

Paul

  • From: B.C.Canada
  • Registered: 2005-01-26
  • Posts: 2,586

Re: Ashy Heat Riser Tube...what could cause this??

Paul

All that matters is that the end of the heat riser tube sticks into the pea shooter the right amount. You can do the math to figure it out. Bentley engine chapter page 10.

jim

'71 SB(DD only 79K(now 84K miles) & '78 FI Westy (project)
PO of '65 Beetle in '69, '70 Crewcab & '70 Ghia in '77
'71 Super inside rear vents now available
http://www.openroad.ca/volkswebbin/view … p?id=85915
  • Registered: 2009-06-25
  • Posts: 554

Re: Ashy Heat Riser Tube...what could cause this??

Thanks Jim, I'll check it out.

Paul