 | Home > Td5 > Hissing noise but no boost leak |
 
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| defender4x4td5 Member Since: 03 Oct 2023 Location: London Posts: 2   
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Hello everyone,
I'm having a problem with my Defender 2006 TD5 and I thought you can help me. I've been noticing some black smoke when hard accelerating. black smoke is more before the turbo kicks in. I thought there might be a boost leak in the radiator pipes, but after testing each part one by one, no luck finding any leak before the air intake. it's holding up the pressure nicely. (from turbo to intake manifold) Then I decided to put pressure (5psi) to the whole system including the engine. there is a noticeable hissing sound, seemingly originating from the rocker cover. To confirm this, I removed the oil cap and the sound became more apparent, I removed the rocker cover and I found the hissing sound coming from the 4th or 5th pistons (maybe both). Worth to mention: There are no signs of oil and water mixing, and no blue or white smoke. The oil and water remain clean. I have blanked the EGR to eliminate any related potential issues. New air filter Oil level hasn’t raised, so I think diesel is not mixing up with the oil. you can see it is louder around the 4th and 5th in this video: https://www.youtube.com/shorts/MBk-UIo_f5Q |
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3rd Oct 2023 6:33pm |
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| barbel jim Member Since: 12 Dec 2012 Location: Northants Posts: 1434 
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I’d start by changing the injector washers.
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3rd Oct 2023 6:43pm |
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| rallysteve Member Since: 10 Feb 2014 Location: Cumbria Posts: 2238 
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Not sure i understand what you are doing here? You are putting an airline into to the intake?
Assuming you havent blanked off the pipe from the intercooler to the inlet manifold then the air is just going into the cylinders and seeping past the rings into the crankcase. 02' 110 TD5 Double Cab Rebuild Thread |
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3rd Oct 2023 7:16pm |
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| geobloke Member Since: 06 Nov 2012 Location: Nottinghamshire Posts: 4410
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If you put pressure into the rocker cover and that was hissing then it is likely the rear half moon portion of the rocker cover seal is no longer sealing properly. Either that or the rocker gas recirculation valve (the one before the turbo).
As for the black smoke before the turbo spools up. First thing to do is make sure the waste gate actuator is functioning properly and not partially open. Second is to check your air filter is not dirty, probably not. Third is to make sure the Ambient, MAF and MAP sensors are all functioning properly. If one is not the ECU could be adding more fuel and hence the black smoke. |
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3rd Oct 2023 7:23pm |
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| barbel jim Member Since: 12 Dec 2012 Location: Northants Posts: 1434
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You’re getting the noise on those cylinders as the valves are not seated. If you turned the engine over, I think you’ll find the noise moves.
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4th Oct 2023 4:53am |
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| excossack Member Since: 22 Feb 2012 Location: North West Posts: 5889 
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I have a hissing noise as well during acceleration. I can hear it more when the vent flaps are open.
A quick look showed no hoses with splits. I was wondering, would spraying brake cleaning fluid be able to detect a leak i.e the induction would suck in brake cleaner and raise the revs? 1999 Defender TD5 110 Regards John M0VAZ Econet Station 48 no clock |
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4th Oct 2023 1:58pm |
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| TexasRover Member Since: 24 Nov 2022 Location: Paris Posts: 1148  
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Hissing under boost could indicate an air leak from the turbo to the intake manifold, which is just pressured air. There are the standard checks as mentioned. It should be fairly easy to make two plugs, and gently pressurize the system from the turbo to the intake manifold using the wastegate hose and listen for leaks. Maybe the intercooler leaks?
However in my experience the air is a little oily from the turbo and any leak will quickly show as being oily and dirty. |
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4th Oct 2023 2:13pm |
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| jpboost Member Since: 13 Apr 2021 Location: Gatwick Posts: 377 
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When chasing air leaks on petrol cars, I always used to use any spray that contained Toluene (my local motorfactors carb cleaner was my go-to product).
The logic being that toluene burns quite rapidly, so if it got sucked into the combustion process, you could hear the engine speed increase. It also evaporates so quickly that you could quite accurately spray certain areas and help pin-point the leaks. I had an old racecar that had really fiddly gaskets on where the throttle bodies bolted to the head, and this was a great way to check they were ok, and pinpoint any that needed re-doing. I'll leave it to someone more experienced in Diesels to say if this would work, or there is an equivalent. I suppose if you're only hearing the issue when 'on boost', then my method would only work if the leak was bad enough to suck air into the charge pipes at idle. |
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4th Oct 2023 2:28pm |
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