| Author | Message | ||
     Robert Gardner Frequent User Username: bobg Post Number: 52 Registered: 12-2012 |
72Shadow; LRA13020 Started the car for the first time in nine months, engine running quite fast and there is a noticeable knocking noise which I never heard before today,Checked the oil level and it is right between min and max, Is this an acceptable level? The answer I'm looking for is " Add a quart and see what happens " Please don't tell me that there could be a myriad of reasons for the knocking noise !! Thanks, Bob G. | ||
| Geoff Wootton Grand Master Username: dounraey Post Number: 1970 Registered: 5-2012 |
Bob There could be a myriad of reasons for the knocking noise. Sorry, but it's true. Where is the knocking noise coming from, the top or lower part of the engine. Have you ruled out a ticking hydraulic pump. Hydraulic tappets perhaps. Could you give some more information. Oil level between min and max is perfectly acceptable. | ||
| Mark Aldridge Grand Master Username: mark_aldridge Post Number: 543 Registered: 10-2008 |
Bob, check the bottom pulley is not loose . I have had this problem with my Mulsanne which I sold recently . Might also be worth trying 200cc of TQF in the sump oil. Mark | ||
| Robert Gardner Frequent User Username: bobg Post Number: 53 Registered: 12-2012 |
TQF ? | ||
| Jim Walters Prolific User Username: jim_walters Post Number: 171 Registered: 1-2014 |
ATF. Automatic Trans Fluid. It has a strong detergent action and will often free up a sticking hydraulic lifter. If it's a tap tap tap then brake pump or lifter. If it's a thud thud thud then you don't want to know. SRH8505 SRC18015 SRE22493 NAC-05370 www.bristolmotors.com | ||
| David Gore Moderator Username: david_gore Post Number: 2916 Registered: 4-2003 |
Robert, As mentioned above, it is most likely a collapsed hydraulic lifter from its recent "holiday", these can take some time to fill with oil and start functioning properly. The ATF addition to the engine oil may but not always help clear the lifter for the future. My experience has been to let the engine idle until it warms up completely before driving the car and this invariably sorts out the recalcitrant lifter. Otherwise Jim Walters comment above applies......use a long handled screwdriver as a stethoscope to listen to the hydraulic pumps to determine if they are the source of the tapping. | ||
| Vladimir Ivanovich Kirillov Grand Master Username: soviet Post Number: 942 Registered: 2-2013 |
Well my experience it that the knocking noise could well be the liners squeezing the pistons. Obviously, the first question would be about the coolant - has it been changed regularly and that in itself given the age of the engine difficult to answer unless there is an accurate record of its maintenance. One could remove the sparkplugs and feel how easily the engine turns over. If its got a lot of resistance the corrosion in the aluminium engine block is squeezing the liners and the liners in turn are squeezing the pistons. Another way to check is to put each piston at bottom of its travel and check for scouring on the liner bores using a borescope. The engine should not be run until the source of the knocking is found and rectified unless you want to use the engine as a boat anchor! | ||
| carlos Maenhout from Belgium Unregistered guest Posted From: 81.242.76.156 |
I have also a knocking noise on my Silver Shadow Drophead Coupe of 1969 SN DRH7762.The knocking is not always there. When it is there, then it is mainly heard when the engine is quite hot after a good drive. I suspect that a hydraulic tappet is failing or dirty., but I am not sure. Where exactly have I to hear the noise with a stethoscope in case a tappet is failing? How much ATF oil can I add in order to clean the tappets and how long should I run with it? carlos (Message approved by david_gore) | ||
| richard george yeaman Grand Master Username: richyrich Post Number: 1041 Registered: 4-2012 |
Hi Carlos try 500 ml and take it for a short drive and see if that alters things if it does change the oil and filter, If it doesn't help try a longer run with a little more ATF Richard | ||
| Patrick Lockyer. Grand Master Username: pat_lockyer Post Number: 2024 Registered: 9-2004 |
I would have a long screw driver and test each hydraulic pump first, if ok then check if it is piston noise when hot, remove one HT lead at a time to see if the noise stops. If ok then use the screw driver along the heads to confirm any sticking valves or hydraulic tappets. | ||
| Carlos Unregistered guest Posted From: 81.242.76.156 |
Thanks for the tip Richard @ Patrick: I will check the hydraulic pumps first. What is the relation betwwen the piston and knocking with HT lead and not knocking once the HT lead is removed? (Message approved by david_gore) | ||
| Patrick Lockyer. Grand Master Username: pat_lockyer Post Number: 2025 Registered: 9-2004 |
If the knocking is still present after the checks being ok with the pumps and hydraulic tappets etc. Removing each HT lead in turn when engine is idling can find the noisy cylinder in most cases, this will show up the knock on a small end (wrist pin), big end, piston liner fault(distortion) etc when hot. Stopping the cylinder firing will lessen the cylinder pressure. BTW piston slap will in most cases get quieter when the engine is hot. | ||
| Carlos Unregistered guest Posted From: 81.242.76.156 |
ok Patrick, now I understand. I let make a lub oil analysis. The copper content is in my opinion quite high: 27 ppm. Are there running copper parts somewhere inside the engine? (Message approved by david_gore) |
