Tap when letting off throttle? valve? - Defender Source
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  #1  
Old November 14th, 2014, 08:56 PM
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Tap when letting off throttle? valve?

I adjusted my valves, timed the injector pump, new timing belt, tuned up the rover pretty well. Got it right around the sweet spot. A bit of extra smoke at speed (50+ mph/load) but I'll hit up the max fuel screw and see where I am with that.

The only thing that bothers me is a "tap tap tap tap" as the engine is winding down when I push in the clutch. Not there at idle and can't hear it at speed.

Sounds like a valve, but it didn't change after adjusting the valves. Very ignorable, not a clunk. But definitely a thing. Sounds a bit worse when hot.

Is this more likely a bearing or is it time to install a radio... as it were.
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  #2  
Old November 15th, 2014, 07:26 AM
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Mine just developed the opposite. Tapping on acceleration.
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Old November 15th, 2014, 09:12 AM
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That , in my non defender experience, is a bent push rod.
But that has always sounded like more of a "clink/clank" than a tick when I've had them. But these push rods are a bit different construction.

Then again, I've rarely had a solid tappet engine. Hydraulic lifters are much more common in my paddock.
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Old November 15th, 2014, 09:28 AM
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You are sure it is in the engine and not the clutch release bearing?
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Old November 15th, 2014, 09:34 AM
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shayne young
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If it only happens when you have the clutch depressed then you may have excessive end float in your crank... When you push the clutch in you are effectively pushing the flywheel and crank forward onto the thrust surfaces of the main bearing thrust face, if clearances are a little excessive it may be allowing something to touch as it rotates..
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Old November 15th, 2014, 09:34 AM
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hard to tell with your description but from experience i would look into your fueling excessive fuel in a diesel causes a tapping or a clacking noise since your getting it when you let off you might have a weak injector allowing fuel into the cylinder. have them pop tested it will determine the condition of the injectors
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Old November 15th, 2014, 11:31 AM
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I do get a good puff of smoke on a down shift/engine brake. Maybe its an injector. Couldn't hurt to replace them all anyway.

It doesn't change with clutch. SLipping it into neutral is the same as clutching. Bad end float on my petrol 2.25 sounded more like a knock than a tap. I mean.. like someone inside the engine trying to get out. "clock clock clock" and it did it at idle. This is only on spin-down. Not at idle.


As of today, I can't hear it. I've really put the spurs to it a couple times. Maybe it was a sticky valve or something that broke free. Maybe driving the rover at 63 mph has ruined my hearing.


I added a bottle of stp oil treatment... just on a lark. Had some space in the crank case and no more oil. "quiets noisy valves" sure, whatever. I also added a significant amount of diesel clean with CETANE BOOST! THis was in effort to make sure I didn't have problems with some DECADES old diesel I put in the tank a few days ago. (I've got 500 gallons of the stuff and it seems to be stored well and work fine, if not smell a bit funny.) Mind you the old fuel was after I noticed the tick.

The engine has a bit of a sewing machine quality to it at speed. Not bad... just how I'd characterize it.

Almost vw beetle from the pea-shooter days.

THanks for the posts.
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Old November 20th, 2014, 12:57 PM
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SO, the tapping is still there... I shouldn't say tap.. its a tick. At speed sounds like a high speed computer fan with a wire touching it.

It joins in the chorus of engine noise it's a bit different... that "sewing machine" noise I eluded to. The only time it sounds like a tick is when the engine is at low rpm. Even under compression it ticks (slowing for a turn or light). disengage the gears and it dies with the engine RPM.

So, its always there, but is only really noticable under load. I can just touch the throttle and it will become louder instantly. No lag. I do not have to push the throttle much. It does not change between light load and heavy load, but is gone under no load. It is not there when I rev the engine in the driveway. It correlates to engine speed and is load sensitive.

Is it possible its a pump, injector, vacuum or lift? More likely an injector? Natural noise and my problem is lack of firewall insulation?

My fear is more of a bottom end bearing or a bad lifter or something. Something that will nuke the engine or wear off a cam lobe. I have good oil pressure. No knocks or thumps. runs evenly and I think strongly for what it is. I can easily make top speed. 69 is the fastest i've gotten it (GPS measured) 65 is easily-ish attainable on a flat. Not that I'd keep it there.

It did not change after a valve adjustment. Seems worse when hot.. but never gone completely.
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Old November 20th, 2014, 01:07 PM
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have you ruled out an exhaust leak
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Old November 20th, 2014, 01:10 PM
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You could run the engine with the valve cover off, by pressing on the rocker arms as it runs you may be able to isolate the noise if it is valve train related.. Not too much oil pressure up there but may splash a little..by cracking the diesel fuel lines at injector or pump you can cut the cyclinder a and see if it changes with a particular cyclinder, by cracking the lines one at a time you also relieve the pressure on that injection plunger, by the combination of these tests you should be able to narrow down a cylinder or component at the very least...
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Old November 20th, 2014, 02:01 PM
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Quote:
Originally Posted by Uncle Douglas View Post
have you ruled out an exhaust leak
I have not. My experience with them has always been that I can hear them at idle. But a diesel might be drowning it out. I'll feel, look for one. Usually a teltale black streak at the site.


The thing that kills me with the valve train is that it sounds fine at idle.
I may just try to run it with the cover off. Usually if ya stuff rags around the exhaust and back of the engine, it works out none too messy.

I'll see what I can accomplish with the above suggestions.
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Old November 22nd, 2014, 04:46 PM
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Ben, Have you inspected for dropped hotspot(s). I read an old post on LR4x4 a guy was having a similar issue which increased with speed. A few posted it sounded like a dropped Hotspot. Ultimately this was his issue but these are known to damage the piston sometimes when this occurs.

Clay
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Old November 22nd, 2014, 05:31 PM
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Quote:
Originally Posted by 1of40 View Post
Ben, Have you inspected for dropped hotspot(s). I read an old post on LR4x4 a guy was having a similar issue which increased with speed. A few posted it sounded like a dropped Hotspot. Ultimately this was his issue but these are known to damage the piston sometimes when this occurs.

Clay
I'll bite. What is a "hotspot" ? A glowplug ?
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Old November 22nd, 2014, 05:46 PM
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Glad somebody asked...lol...
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Old November 22nd, 2014, 06:06 PM
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Ha! I thought I was the only one. Below is the response to the same question on LR4x4.

On the N/A and T/D engines, the hotspot is a hardened steel (?) 'cup' that covers the tip of the injector. These engines have a flat top piston, which means that the burn happens immediately outside of the hotspot - concentrating combustion to the centre of the piston crown and forcing the piston down on it's ignition stroke. The later TDi engines have a recessed piston crown and no hotspot - the tip of the injector being slightly proud of the head face and aimed at the centre of the piston. Combustion therefore happens within the piston, which is shaped so that pressure is evenly distributed. The 'Di' stands for 'Direct Injection', which refers to the fuel being injected directly into the combustion chamber (the recess in the top of the piston crown).
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Old November 22nd, 2014, 07:10 PM
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So... What am i checking for then? Like ... A broken... Uh?

So. The hotspot is a part of the head? A part of the injector or acreted material?

------ Follow up post added November 22nd, 2014 07:17 PM ------

Its one of those noises that, if im thinking about work or something it goes away... If i get to listening for it... It drowns out all. Maybe i'm psychotic... the alien insect under my fingernail thinks i am.
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Old November 22nd, 2014, 07:20 PM
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Hot spot../ also Called a pre-combustion chamber..?? ...and I was under the impression that the tops of the pistons were swirl chamber design..I.e. As the forced fuel is sprayed onto the top of the piston it creates a swirling motion which aids in better atomization of the fuel for a cleaner more even burn. Also reducing piston slap and noise due to the combustion not being one sided..

------ Follow up post added November 22nd, 2014 07:28 PM ------

I have a 2.5 TD head off at the moment.. I can take a pic if you like, but when I pulled this head off all the pre chamber cups are loose.. Can't see why it would make a noise on decal as opposed to all the time though, it's pressed I to the head by the head gasket..
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Old November 22nd, 2014, 07:57 PM
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So, initially I thought it was only on decel but that's just when it slows down and sounds like a tick instead of a... i don't know... rotary pump.

I don't know if it got louder or if I just picked it out. I did a lot of tuning, so ... might have made it more noticeable or increased it. If i were to take a guess on what it was, I'd think it was the fuel pump rod.

I recorded a video. Don't know how it will sound. I can hear it... but I know what to listen for. Sounds like a heater fan with a leaf in it. Speeds up and down with engine. The funky throttle work is me trying to make it more obvious, not missing. I like/hate the combustion chamber idea. It sounds plausible. It sounds like a pain in my ass.


On my little net book, it sounds like high pitched wind noise. But there is no wind noise in the video. Road roar, diesel sound and that... well fan noise thing. When I slow down to make it sound like a tick, the windows rattle and the recorder really picks that up drowning out everything.
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Old November 29th, 2014, 11:16 AM
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I think that tick has progressed.. or I found something else.

I think its a knock. It may not be what I hear when driving... its outside end possible that its a normal noise
I hear this knock from the water pump. loudest from the inlet pipe area.

Sounds like the red october on on when I stethoscope the water pump inlet. (45 seconds in)

I might be paranoid... I was trying to see if I had an exhaust leak. Everything is tight.. and even when I loosen the down pipe it doesn't leak audibly. Would it be normal to hear the first piston like that or is the cam dead? I cannot hear it anywhere else other than around that area. very very faintly anywhere on the timing cover progressively louder as I get to the water pump. But it does it with the belt off.
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Old November 29th, 2014, 02:18 PM
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I didn't know Jonesy was BLACK..!!! that explains.....alot...
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