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+--- Thread: flex plate sounds when cracked or broken (/showthread.php?tid=2976)
flex plate sounds when cracked or broken - unaleman - 09-15-2011
Hi folks, I just bought a 1985 "euro" 300TD complete with ABS brakes and no egr exhaughst...the problem is it has a bad knocking sound... timing is dead nuts 24* as measured with a-b light at 14*atdc and the bubble method(blowing into the pump while bringing the crank up to 24*) works perfect by the way. valves adjusted twice. I listened to it with a mechanics stethoscope and it sounds loudest at cylinder three. alternator is quiet so is water pump; vacuum pump is quiet too. Car lights right up, no smoke, good oil pressure, and kicks right off but man does it CLACK under load also when you first start it it sounds so good then as it warms it ticks then clacks. OH yes I pulled the prechambers all had good attached balls wire wheeled them clean checked for only one seal washer under them and new heat shields with the "new" injectors. injectors changed for known good (quiet set)set. car shifts really well, has great power, temp stays a needles width off the 80* even when I horse whipped it up nine mile hill during a diesel purge...I think a bad tensioner would be a whirring noise..correct? There is a thread at peachparts that indicates that a bad or broken flex plate could sound like a rod knock OR its time to look for a decent block. Anybody have experiance with broken flex plate. NOT flex DISC flex plate. Thanks in advance for you time in responding.
RE: flex plate sounds when cracked or broken - Hercules - 09-17-2011
The flex plate usually makes a tinny or clanging some times chirping sound while starting,shutting off, accelerating or decelerating . Is possible that torque converter could make knocking sound if flex plate were broken,but not knocking in #3 cyl.area. IMO piston contacting cyl.head. Pull lower pan,check rod movement,or remove bearing cap.
RE: flex plate sounds when cracked or broken - dieselboy - 09-17-2011
Swap delivery valves in the pump with another cylinder and see if the problem follows it. You may have a bad delivery valve.
RE: flex plate sounds when cracked or broken - Hercules - 09-18-2011
Yes,Dieselboy I agree,bad delivery valve can allow a secondary injection,which could cause a knock, Good call,forgot about that one.
RE: flex plate sounds when cracked or broken - unaleman - 09-18-2011
Thanks Dieselboy and Hercules, the delivery valves LOOK like they are new (shiny brass holders) I don't see, other than the barrel? part being upside down- as far as the grooves go what could be wrong- with them I suppose the spring could be bad or compressed- caught under the holder- but it seems to me that then it would miss and you could isolate the miss by cracking the line(s). Will try the suggestions today Thanks for your thoughts.
RE: flex plate sounds when cracked or broken - Captain America - 09-19-2011
My Flex plate In my Sprint spider cracked.... More of a high pitch "ting ting ting" sound. Like hitting a sheet metal oil pan or valve cover with a ball peen hammer kinda noise. Make noise with and without load...
Hard to see in the small pics, but basically spider cracks everywhere, the white lines are cracks too
Loose torque converter bolts will make the same sounding knock noise
RE: flex plate sounds when cracked or broken - unaleman - 09-19-2011
Wow great! I pulled the cover off of the trans (access hole for the torque converter bolts and they were tight with no cracks visible- at least at the bolts themselves- but your pictures show cracks at the center where I would expect them, which is good in terms of extending the hope that I don't really need a new motor.. I did say Clack but it is very like a hammer hitting metal and you do not hear it as a sound from the block it is not deep AND there is at least one you tube video of a similar noise where the guy indicates that it was the flex plate.. thing about the video that got my hopes up is that he says the sound is coming "from around here"
as he has his hand just behind the turbo and that is exactly where this sound is coming from on mine..SO... should I pull the tranny back a bit or pull the engine and tranny
la
RE: flex plate sounds when cracked or broken - DeliveryValve - 09-19-2011
Here are my pictures of a crack flex plate. The noise was horrible! You could easily tell it was coming from the back of the engine.
Enjoy.
RE: flex plate sounds when cracked or broken - unaleman - 09-19-2011
Hi thanks, yes I have seen those pictures in my searching.. I just started and moved the car about twenty feet.at start up, once again it sounds fine... it is when you come off idle that you begin ti hear the sound and as it warms up or you go for a drive the sound gets progressively louder/more prominent.. it never sounds like it is coming from that area and the mercedessource article/ alert indicates people have been fooled by the sound. I read that torque convertors actually "swell" as they warm up or fill or pump up.. the sound does not have that deep quality of a crank/rod journal and I dont know what a wrist pin would sound like or piston slap but it seems to me those would be constant .. thank you I'm going to pull the trans this evening.
RE: flex plate sounds when cracked or broken - dieselboy - 09-19-2011
You have a way to make a video?
RE: flex plate sounds when cracked or broken - Captain America - 09-20-2011
Yeah it will make a hollow ting ting ting noise. let us know!
RE: flex plate sounds when cracked or broken - winmutt - 09-23-2011
You should be able to inspect the flex plate via the inspection hole easily and sufficently enough to rule out flex plate. I vote rod/delivery valve. Crack #3 injector line with car running and report back.