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05gh
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Joined: September 01, 2011
Posts: 157
Location: The Netherlands
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 Posted: Thu May 31, 2018 2:45 pm Post subject: non return flaps missing in type 4 fan schroud |
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due to oil leakage I had to clean the fan shroud and discovering that the no return flaps are missing. What is the function? and should I rebuild it
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79 de luxe micro bus
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ivwshane
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Joined: May 19, 2011
Posts: 1920
Location: Sacramento ca
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Tcash
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Joined: July 20, 2011
Posts: 12844
Location: San Jose, California, USA
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Wildthings
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Joined: March 13, 2005
Posts: 50352
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| Posted: Thu May 31, 2018 8:34 pm Post subject: Re: no return flaps missing in type 4 fan schroud |
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Unless you are putting your engine in a Type 4 car with a working gas heater don't worry about the ones in the fan shroud as they make little or no difference in the heater output. The ones in the heater booster fan are necessary though.
The ones in the fan shroud tend to break partially off and hang sideways or break fully off and get blown into the heat exchanger, either of which will reduce heat output. I have been running my engines without them for nearly 30 years after having both of the above failures occur and haven't missed them a bit. |
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gintaras
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Joined: November 19, 2012
Posts: 523
Location: Louisville
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| Posted: Thu Jun 14, 2018 4:40 pm Post subject: Re: no return flaps missing in type 4 fan schroud |
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| Wildthings wrote: |
Unless you are putting your engine in a Type 4 car with a working gas heater don't worry about the ones in the fan shroud as they make little or no difference in the heater output. The ones in the heater booster fan are necessary though.
The ones in the fan shroud tend to break partially off and hang sideways or break fully off and get blown into the heat exchanger, either of which will reduce heat output. I have been running my engines without them for nearly 30 years after having both of the above failures occur and haven't missed them a bit. |
So, are you saying that if my internal flaps are bent, don't even bother trying to fix them, just pitch them? Are we talking about the 2.5"x1" little flimsy flaps?
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Wildthings
Samba Member
Joined: March 13, 2005
Posts: 50352
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| Posted: Mon Jun 18, 2018 6:21 pm Post subject: Re: no return flaps missing in type 4 fan schroud |
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| gintaras wrote: |
| Wildthings wrote: |
Unless you are putting your engine in a Type 4 car with a working gas heater don't worry about the ones in the fan shroud as they make little or no difference in the heater output. The ones in the heater booster fan are necessary though.
The ones in the fan shroud tend to break partially off and hang sideways or break fully off and get blown into the heat exchanger, either of which will reduce heat output. I have been running my engines without them for nearly 30 years after having both of the above failures occur and haven't missed them a bit. |
So, are you saying that if my internal flaps are bent, don't even bother trying to fix them, just pitch them? Are we talking about the 2.5"x1" little flimsy flaps? |
When I bought my first Type 4 powered Transporter years ago, I tried to get everything as close to factory as I could, including installing the best set of flaps I could come by. Over the years I experienced flaps failing on one end and getting cocked and jammed in the opening and also breaking off entirely and jamming against the fins in the heat exchanger. Having had to tear into the exhaust multiple times to fix things, I eventually decided that removing the flaps was the best solution, and have not missed them a bit as they do nothing on a Type 4 engine when installed in a Transporter.
If you were to install an electric fan that put out 3-4 times the output of the stock heater booster fan, then they might actually do something, but with the anemic stock booster fan they just don't do anything.
If you want more heat from your heating system read the Blumax thread and follow the ideas therein. By doing the correct upgrades you can get 3 or 4 times the heat into the passenger compartment. |
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Tcash
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Joined: July 20, 2011
Posts: 12844
Location: San Jose, California, USA
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| Posted: Mon Jun 18, 2018 7:38 pm Post subject: Re: non return flaps missing in type 4 fan schroud |
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Thanks to Mayor Ratwell
72-79 Bus Heating System
http://www.ratwell.com/technical/Heating.html
| ratwell wrote: |
The booster fan has a powerfull motor.
The other two flaps are in the base of the fan shroud and prevent air from the booster fan from re-entering the engine compartment. Often if there has been exhaust modifications the flaps have been lost or left out. Sometimes they have unknowingly fallen off while driving. They are held in place by a simple pin so if you ever have someone work on your engine be around when they are about to put the fan shroud back on. You will notice (or never have known that you lack) a serious lack of heat if you are missing these flaps. |
Tcash |
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Wildthings
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Joined: March 13, 2005
Posts: 50352
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| Posted: Mon Jun 18, 2018 10:02 pm Post subject: Re: non return flaps missing in type 4 fan schroud |
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| Tcash wrote: |
Thanks to Mayor Ratwell
72-79 Bus Heating System
http://www.ratwell.com/technical/Heating.html
| ratwell wrote: |
The booster fan has a powerfull motor.
The other two flaps are in the base of the fan shroud and prevent air from the booster fan from re-entering the engine compartment. Often if there has been exhaust modifications the flaps have been lost or left out. Sometimes they have unknowingly fallen off while driving. They are held in place by a simple pin so if you ever have someone work on your engine be around when they are about to put the fan shroud back on. You will notice (or never have known that you lack) a serious lack of heat if you are missing these flaps. |
Tcash |
There is no condition where with the engine running the cooling fan does not produce some pressure as that statement implies, while the tiny motor on the booster fan is anything but powerful, it is totally overcome by the cooling fan at around 1000-1200 crankshaft rpms when its weak output is reduced to zero. |
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Bleyseng
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Joined: July 03, 2005
Posts: 4752
Location: Seattle
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| Posted: Tue Jun 19, 2018 6:45 am Post subject: Re: non return flaps missing in type 4 fan schroud |
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They make a difference at idle so you still get a decent amount of hot air to say defrost the windshield. That's my take in 40 years of fooling with these things
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