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| Loud Hiss at Idle on Startup from Cold http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=56449 |
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| Author: | DOC4444 [ Sun Oct 24, 2010 3:18 pm ] |
| Post subject: | Loud Hiss at Idle on Startup from Cold |
I just noticed a new sound at idle on cold startup with the CRD. It sounds like a fairly loud vacuum leak "hiss". However, even with the decorative engine cover removed, I can't seem to pinpoint the source. It sounds like it is coming from the top of the motor in the area of the injectors, but there are no hoses/airlines in that area, so it is probably a "referred sound". The engine driven fan blows a lot of air even when it is supposedly not "engaged", making pinpointing the source much more difficult. (No CEL or stored codes from my scanner.) In any case, the sound starts to fade after 2-3 minutes of running at idle and completely goes away in 5 minutes. (You can't hear it above idle, but I don't know if the sound is being drowned out or if it actually goes away at higher engine speed.) It does not come back on restart until it has sat overnight and fully cooled down. Any thoughts? Thanks, DOC |
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| Author: | Joe Romas [ Sun Oct 24, 2010 5:33 pm ] |
| Post subject: | Re: Loud Hiss at Idle on Startup from Cold |
On VW tdi's the glow plugs remain on for a while after a cold start and a noise can be heard from alternator because of the current drain. Could this be what your hearng? |
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| Author: | DOC4444 [ Sun Oct 24, 2010 6:18 pm ] |
| Post subject: | Re: Loud Hiss at Idle on Startup from Cold |
Joe, Interesting thought, but this is a "new" sound and do you think the glow plugs stay on for up to 5 min when it's 45 degrees? Thanks, DOC |
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| Author: | kccrd [ Sun Oct 24, 2010 6:34 pm ] |
| Post subject: | Re: Loud Hiss at Idle on Startup from Cold |
The glow plugs should stay on for 5 seconds max. Have you checked your cac hoses you could have a split in one of those, maybe the hose coming from the turbo to the intercooler. Inspect those real good top and bottom I have had to replace both of mine in the last 2 years. |
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| Author: | Joe Romas [ Sun Oct 24, 2010 7:09 pm ] |
| Post subject: | Re: Loud Hiss at Idle on Startup from Cold |
kccrd Just because the glow plug light goes off does not mean the glow plugs are not still on. DOC444 They're left on to cut polution but I doubt it's five minutes though. Maybe Mr Mopar or Green diesel will comment. |
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| Author: | kccrd [ Sun Oct 24, 2010 7:37 pm ] |
| Post subject: | Re: Loud Hiss at Idle on Startup from Cold |
I have had 2 jetta tdis and a eco diesel and a 79 diesel rabbit and the longest the glow plugs stayed on was about 25 seconds on the 79 with the slow glow system. The last being my 98 tdi had the quick glow system and they only stayed on about 5 to 8 seconds max. I do not see any reason to stay on once the engine is running I thought the glow plugs were only to heat up the combustion chamber for starting and to ease ignition of the fuel. |
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| Author: | Joe Romas [ Sun Oct 24, 2010 8:41 pm ] |
| Post subject: | Re: Loud Hiss at Idle on Startup from Cold |
kccrd> Here's a thread where "afterglow" is mentioned. viewtopic.php?f=5&t=37781&hilit=afterglow I've owned at least 12 VW diesels I can think of right off, maybe more. The first was a new 1978 rabbit and the last were a 1996 Passat tdi wagon and a 1999.5 tdi Jetta. There were many 1985/6 golfs and jettas, a 91 EcoDiesel, a 91 normal diesel, a 1986 Volvo 740 GLE wagon powered by a VW 6 cylinder turbocharged light truck engine. Then there was a 1982 Datsun Kin Cab diesel that I kept foe less then a year. It was too much like a low reving semi truck engine for me. I know for a fact the glow plugs on the TDI's continue to operate after the light goes off and it's for smooth running and emmissions. By the way, the original glow plugs on the 78 rabbit could stay on for upwards to a minute before the light went off. OK I just remembered two more. A 1984 Rabbit diesel that was my Daughter's first car and a 1984 Jetta diesel that was my son's first car. |
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| Author: | DOC4444 [ Tue Oct 26, 2010 3:17 pm ] |
| Post subject: | Re: Loud Hiss at Idle on Startup from Cold |
Keith @ GDE wrote it off as "cold weather turbo airflow resonance" and thinks it is nothing to be concerned about. DOC |
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