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Red Hot Heat Riser
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James Watt
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PostPosted: Wed Apr 26, 2017 8:36 am    Post subject: Red Hot Heat Riser Reply with quote

Hi All,

I have an issue with my 77 westfalia bus.

I have had this issue since I bought the bus four years ago and even after an engine rebuild it is still just the same.

When I start my engine, for the first 5 seconds the engine sounds OK and then you can hear the noise change as 1 or 2 cylinders stop firing. This continues for about 20 30 seconds until the engine warms a little and then all cylinders fire again. It certainly is heat related as if you start the engine when warm this problem does not happen. Only on the first start of the day.

I had been suspecting a vacuum leak as I also have an erratic idle and need to adjust the idle speed to be quite high to get the engine to run. However, I have tried spraying WD40 on all possible joints and cant find any obvious big leaks.

I am starting to question the function of the heat risers and if mine could be blocked or the exhaust system is not installed correctly.

The left side heat riser tube gets red red hot, as you can see in the photo of bus taken recently, whilst the right side only ever gets lukewarm and as you will see the paint has not burnt off. Is it normal for one side to get that hot?

When I bought the bus it had a strange 4 pipes exhaust system which was all rusty so I replaced it with a stock 1600 exhaust. However as you can see from the photos when I bought the buss the left side heat riser was black and obviously had not seen the same heat as it is seeing now. Worth noting is that my exhaust tail pipe is on the left side, the same side as the red hot heat riser. Is that normal?

Any help is much appreciated as always.

Thanks Guys.

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Xevin
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PostPosted: Wed Apr 26, 2017 8:47 am    Post subject: Re: Red Hot Heat Riser Reply with quote

Interesting engine swap to a type 1. Can you give more details about the engine? Also since it's a type 1 engine I suppose the exhaust being on the left would be fine. Like an early bay.
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TomWesty
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PostPosted: Wed Apr 26, 2017 9:19 am    Post subject: Re: Red Hot Heat Riser Reply with quote

I probably sound like a broken record on this.... Remember those? Anyway, check that your line to the brake servo isn't leaking vacuum. I don't know how the vacuum plumbing is handled on a bus that has had a swap like yours from type 4 to type 1. But remove the vacuum hose from wherever it connects to the manifold and plug the hole in the manifold. If you drive it like this your brake pedal will require a lot more pressure so be forewarned. If your idle improves, you have a vacuum leak upstream of the manifold port. Could be the hose, could be the servo. If no change, obviously unplug the manifold and restore the hose....
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Wildthings
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PostPosted: Wed Apr 26, 2017 9:26 am    Post subject: Re: Red Hot Heat Riser Reply with quote

It is normal for the paint to burn off of the heat riser. With the OEM style exhaust the hot gases flow from one side to the other and not back and forth as do with many aftermarket exhaust, so to have the paint burnt from only the one side is normal.

Have you checked the adjustment of your choke including the choke unloader? A tiny adjustment can make a big difference in how the engine runs for the first few minutes. Remove the intake elbow from the top of the carb prior to a cold start and then once you start the engine go back and manipulate the choke butter fly with your fingers to see if you can improve on how it runs. You can also mostly close off the air horn with the palm of your hand and see what effect that has.

Anything that cause the exhaust to run hotter than normal would add to the temperature of the heat riser. Delayed timing, incorrect mixture, air leaks into the exhaust, an exhaust valve that isn't closing fully, etc could all cause the exhaust gases to be hotter than normal.


Last edited by Wildthings on Wed Apr 26, 2017 12:29 pm; edited 1 time in total
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James Watt
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PostPosted: Wed Apr 26, 2017 11:08 am    Post subject: Re: Red Hot Heat Riser Reply with quote

Hi guys.

It is a interesting engine swap! I think when the bus came to the UK about 8 years ago the nice type4 engine was robbed for its high value. What's fitted is a bit of a frankestein type1 1600 dual port.

OK I shall double check the brake servo line. It looks simple, just a pipe running from services to manifold with a valve close to the manifold.

That's good to hear paint burning off is normal, thank you. I'm fairly confident it is not the choke to blame as I even have the choke disconnected and left fully open last summer and the start up was the same.
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PostPosted: Wed Apr 26, 2017 11:19 am    Post subject: Re: Red Hot Heat Riser Reply with quote

I like the air cleaner - I've never seen anything like it before. May be a Frankenstein but it looks like it's well done
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James Watt
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PostPosted: Wed Apr 26, 2017 11:34 pm    Post subject: Re: Red Hot Heat Riser Reply with quote

yeah, i'm guessing the man who swapped the engines was stuck with the air cleaner bracket already fitted inside the engine compartment so had to find a air filter box to suit. not sure what it is from but is easy enough to source new filter elements for it.
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James Watt
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PostPosted: Thu Apr 27, 2017 12:12 pm    Post subject: Re: Red Hot Heat Riser Reply with quote

Hi guys,

So I tried checking NY brake booster line this evening by disconnecting it from the intake manifold and oluging the manifold.

Unfortunately I the engine starts and behaves exactly the same.

Nice first 5 seconds. Then 2 cylinders for half a minute and I need to give it throttle, then all cylinders start firing and the idle speed takes off over the next two minutes and probably settles about 1300.

I felt the heat risers just at the end of the 2 minutes, the left side was getting very hot to the point it burnt my finger. But the right side I could grasp even where it connects to the exhaust and it was only a bit warm. The carb base and inlet manifold immediately below actually felt quite cold even after 2 minutes. But the ambient temperature was low at about 5-6C.

But is it normal that the heat risers are so different in temperature?

Also, I lay might tool case under the exhaust by mistake and it was covered in black wet spots after I ran the engine. I put NY finger in the exhaust and it came out jet black, like I'd just touched coal or something. Is my engine in bad health?
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lil-jinx
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PostPosted: Thu Apr 27, 2017 12:52 pm    Post subject: Re: Red Hot Heat Riser Reply with quote

What are you timing at,I see your distributor vacuum can in one pic and gone in the next pic.
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PostPosted: Thu Apr 27, 2017 1:17 pm    Post subject: Re: Red Hot Heat Riser Reply with quote

Hi lil jinx.

To be honest I don't know. I leave the tuning to my mechanic. Made a massive balls of it when I tried.
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Wildthings
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PostPosted: Thu Apr 27, 2017 1:43 pm    Post subject: Re: Red Hot Heat Riser Reply with quote

James Watt wrote:
Hi guys,

So I tried checking NY brake booster line this evening by disconnecting it from the intake manifold and oluging the manifold.

Unfortunately I the engine starts and behaves exactly the same.

Nice first 5 seconds. Then 2 cylinders for half a minute and I need to give it throttle, then all cylinders start firing and the idle speed takes off over the next two minutes and probably settles about 1300.

I felt the heat risers just at the end of the 2 minutes, the left side was getting very hot to the point it burnt my finger. But the right side I could grasp even where it connects to the exhaust and it was only a bit warm. The carb base and inlet manifold immediately below actually felt quite cold even after 2 minutes. But the ambient temperature was low at about 5-6C.

But is it normal that the heat risers are so different in temperature?

Also, I lay might tool case under the exhaust by mistake and it was covered in black wet spots after I ran the engine. I put NY finger in the exhaust and it came out jet black, like I'd just touched coal or something. Is my engine in bad health?


My post above still applies.

Black specs coming out of the exhaust is also perfectly normal, especially if your choke needs adjustment.
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James Watt
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PostPosted: Thu Apr 27, 2017 2:04 pm    Post subject: Re: Red Hot Heat Riser Reply with quote

Hi Wild Things,

Thanks for the reply.

I think i may go and pull the engine and give the intake manifold and heat riser a good inspection. i think there may be a bit of a air leak at the rubber boots, so shall make this good and see how the engine runs after this.
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PostPosted: Thu Apr 27, 2017 7:25 pm    Post subject: Re: Red Hot Heat Riser Reply with quote

Maybe the riser is clogged, very common.
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PostPosted: Thu Apr 27, 2017 8:06 pm    Post subject: Re: Red Hot Heat Riser Reply with quote

I took this after the engine was fully warmed up, so you can get a feel for what the "hot side" of the heat riser should be like. I say "hot side" because my muffler flows the exhaust backwards from yours, but there is no functional difference in regards to the heat risers.

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If you want to investigate a closed riser, my propensity for "less work, more beer" would result in my removing the muffler with the engine in the car, then threading some weed whacker string through the heat risers to check for clarity. If no go, chuck a few inches of old clutch cable in a drill SET ON REVERSE/CCW and "drill" the cable in. You'll need 4, 6, 10, 16, and 24 inch segments to do it right, since you can't push a rope.

Can you IR thermometer your left hand heat riser after a god drive? Clogged will show about 100-250, while open will be much more.

Robbie
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PostPosted: Thu Apr 27, 2017 10:41 pm    Post subject: Re: Red Hot Heat Riser Reply with quote

Damn, Robbie agrees...holla!
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James Watt
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PostPosted: Fri Apr 28, 2017 12:29 am    Post subject: Re: Red Hot Heat Riser Reply with quote

Hi Robbie,

Thanks very much for the message. We may have a IR heat gun at my work, I will check and see.

Are you working F or C ?

James.
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James Watt
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PostPosted: Sun May 07, 2017 1:46 pm    Post subject: Re: Red Hot Heat Riser Reply with quote

Hi Guys,

I've taken out my engine and stripped off the parts.

couple of questions.

1. Heat risers are not blocked but it takes a really hard blow to get air out the other side, does this mean they are likely to be blocked a bit?

2. Intake manifold boots - The ones that came off are original VW parts (029 299 477. They seem to be in ok condition and quality wise are better than the silicone replacements i bought. Which should i refit?

3. Intake manifold elbow - One of the elbows has a strange little stub of pipe connected to it with a short length of old fuel pipe and blanking bolt in the other end. What would this have been for? a vacuum line for something?
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Brian
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PostPosted: Sun May 07, 2017 2:43 pm    Post subject: Re: Red Hot Heat Riser Reply with quote

1. Yes.
2. If the old ones are good might as well. The new ones suck.
3. Two piece throttle positioner. If just leave it as is until you get the rest of that system in place.

I think it's a right of passage for Type 1 owners to clear out a heat riser.
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PostPosted: Mon May 08, 2017 12:25 pm    Post subject: Re: Red Hot Heat Riser Reply with quote

James Watt wrote:


3. Intake manifold elbow - One of the elbows has a strange little stub of pipe connected to it with a short length of old fuel pipe and blanking bolt in the other end. What would this have been for? a vacuum line for something?


My guess would be for your power brakes. How much force does is take to apply your brakes?

Pictures always help Wink
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PostPosted: Mon May 08, 2017 1:27 pm    Post subject: Re: Red Hot Heat Riser Reply with quote

James Watt wrote:

Are you working F or C ?


Good 'ol Farenhate. 388 F, so 189 C. I post most of my temp readings in Yankee Units because my pictures get used in other forums on here, which are largely based in the U.S.

A power coating shop will be able to blast some media through the heat riser to clean it fairly easily, then they can blast it so you can paint it. Cool

Good luck!
Robbie
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