Hi, I’ll try here as well on your recommendation in the community and maybe we’ll find a solution together. Nissan Cabstar engine BD-30ti year of manufacture 1998. The sound bit like an owl - howling - blowing can be heard in the cabin and outside. I can hear it most from the space between the box and the cabin when I get out of the car on the driver’s side. But obviously also inside. On the other hand, from the same place, it is not as strong. It seems to me that this sound can also be heard from the front around the radiator. stethoscoped the pulleys, pump, etc. in the engine bay for resonance and found nothing extra. Likewise, nothing from the gearbox, the bottom of the engine. A couple of phone recording trips while driving in the areas of the differential (LSD), transmission, engine pulleys and they don’t seem to have this sound coming from them. The last recording from the space behind the cabin and it’s clear there. I can hear it even at idle, the sound does not increase significantly with the engine speed, it does not change frequency. Only in the bottom ones can he sometimes blow his horn even more. It seems constant to me, even with speed I don’t think it changes much. It sounds like slow driving in a convoy even with full power in the pull and freewheeling in a rocking rhythm. Depressing the clutch doesn’t affect it, the sound is still there. I was pretty sure it was from the diff and nothing. The most audible is around 50 km/h. Anyway, the sound is still there. Cold, warm, clutch, off, in neutral, in drive, under throttle, off throttle, etc. It’s quiet when driving without the engine (turned off while driving). I’ve already tried everything. Remove the V-belts, listen to the engine and chassis with a stethoscope, thicker oils, pressure lubrication of the cardan, check the intake and turbo hoses, check the pulleys… Also for bad Input Shaft Bearing - the noise does not change when the clutch is depressed (vehicle is stationary at idling speed)…
No experience w/your vehicle, but howling sounds can occur in fuel injected engines if there’s a slight air leak in the intake boot between air filter and throttle body. PCV system leaks as well. Suggest to do a visual check of those systems. The problem w/this theory is that the stethoscope method, presuming you checked around the engine compartment, would usually discover it.
Another idea, since it also occurs coasting in neutral, wind noise. Try rolling windows up and down, any effect? Any recent changes the the vehicle’s exterior surfaces?
Hi, thanks for the knowledge. Yes, I have an ether-based spray ready to check the intake and hoses. I will check the vacuum suction of air from the cracks in the hoses and around the injection with this starting spray. The car sat for two whole years, the car was not taken care of much and there is a lot to be done. I could also state in advance that this car has almost no electronics and no OBD port at all. It doesn’t even have a Mass Air flow Sensor behind the air filter…
Ah, I have to look in the service manual, but I don’t think it says anything about obd1 either. But I don’t see any quantity or pressure sensor on the hoses. In the service manual, there is no sensor in the intake system, only air preheating. I’m going to look at it. Some (probably luxury…) models from the same years had electronics and visibly have a maf sensor and an obd port. Mine is from 98, a really basic model without a tilt cabin and other elements. But there is an LS differential.
98? hmmm … Suggest to tell the folks here more about the engine configuration. Turbo or no-turbo? Fuel injection or electric-controlled carburetor? O2 sensors? Cat? Do diagnostic codes get stored in an electronic memory when fault detected, that can be read out by setting a test-mode jumper & looking at a blinking a dash panel light, sort of like Morse code?
I haven’t looked into it further. It really is a base model with a garet turbo, a classic positive pressure actuator. The injection will probably be classic, no modern. Nissan Bd30ti 3.0l engine - I think something similar was put in 4x4 Nissans, or they liked to change it for this engine. Distributions are handled by gears - no belts or chains. A very spartan model in terms of electronics, it just runs until it falls apart Don’t even look for a catalytic converter.
It hums even when idling while standing still (slightly different in the swinging rhythm), or when driving in a line of vehicles (constant howling). On the recordings in the links, from the beginning of the recording, there is also standing and the sound of idling, or slow driving.
I’m not able to listen to audio files. Since it makes the sound stopped at idle, that seems like locating the area where it is coming from should be pretty easy. You’ve used the stethoscope method to try to isolate what part of the vehicle the sound is coming from and still not finding the source ?? … hmmm… what sort of stethoscope did you use? For that sort of problem I’d usually use a length of old garden hose as my sound-locating stethoscope.
first an iron rod with a plastic bottle at the end, later I bought a stethoscope for mechanics. So far I haven’t been able to get that sound from either side. I can’t find the sound I’m looking for. This car does not have a tilt cabin, there is no good access to everything.
Today I wanted to strip the car a bit for better access to locate the sound and check the hoses more thoroughly, the engine is accessed sideways through the front wheels. But it was impossible to unscrew the wheels. Two keys destroyed, the screws are fine, they just hold as well as they can. Neither moved. Yes I used a long lever with a steel rod tube no chance. The screws are sprayed with grease, I’ll let it work overnight and wait for tomorrow maybe they will go better.
Power steering, alternator and water pump pulleys seem fine. The V-belts were removed and the car was driven. Sound still present. When listening with a stethoscope, noise can be heard from the power steering tubes even when it is disconnected. Do I still suspect the main pulley directly from the crank? It has a visco clutch for the cooling fan and it is a little stiff.
Another noise came from the vacuum depressor, which is behind the alternator and is driven by the same shaft. Alternator is newer, depressor seems old. However, the noise is normal, after removing the V-belt, it is also eliminated.
Tomorrow I want to check the turbo better, for now I checked the hoses and with my finger if there is any play on the turbine shaft and if the blades are ok.
The engine can be accessed through the interior of the cabin through the passenger seat and from the side of the vehicle through the front wheels. There is currently poor access to the places that need to be checked. And it’s not coming from the top of the engine or the bottom.
Perfect, thanks, I didn’t know that trick with the hose. Today I finally loosened the front wheel bolts with a proper tool and gained access to the side of the engine. Checking the turbo, hoses and leaks. I couldn’t locate the sound and I remembered your trick with the hose. I don’t want to get ahead of myself, but the sound probably comes from the visco clutch of the fan or the main crankshaft pulley. Everything else was disconnected and the visco clutch of the fan is just on the main pulley which is always in motion and it was therefore difficult to locate its sound with a type of stethoscope based on contact and resonance. The car is being prepared for fan removal and inspection tomorrow.