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MG TD TF 1500 - Engine tapping
|When I first start up my TD there is a slight tapping (Sounds like valve tappets). Oil pressure is good. (60 pounds). When I go down the road if I swerve it back and forth (Like heating up the tires on the race car) the tapping goes away. It's like I have to swoosh the oil around. It only happens whe I start the car up cold. If I have run the car and stopped for about 15 20 minutes its fine. I also noticed it more after I changed the oil. I am running Castrol 20-50 with Cam-Shield.|
I cannot help you but am curious as to the replies that you will receive.
Do you have the restrictor in the upper banjo fitting for the oil line to the head? I do, and I have a tapping every time I start from cold, which goes away after about a minute or two of idling. I've always attributed it to the restrictor to cause the lower pipe take off point (and hence the oil gauge take off point) to see an oil pressure more represntative of what the pump is delivering. As a rule, I don't start driving the car until the tapping is gone.
Does the tapping ever go awaw without the 'swoosh' manuever by simply waiting?
I have let the car idle for some time and the tapping does not go away. I have owned the car for 2 years and was what I would call normal until and I would say that I noticed it more after I changed the oil.
|I think I'd try and determine where the tapping is coming from. I don't own a stethescope so I'd get out the rubber hose and have a listen and try to figure out what area of the engine it's coming from.|
|David, that's the best excuse for hooning around I've heard for a while! Can't you just see it; "Well, Officer, it's like this ...... ".|
|you can also use a long screwdriver to "sound out" the engine. what is your tappet clearance? regards, tp|
|Tom is right... it's not unheard of for a tappet to go out of tolerance, and it is a coincidence that it happened with the oil change, and yet is not so far out of tolerance that once oil is in the valve train the sound is muted. Perhaps a valve adjustment is in order.|
Also, the 'cam shield' or the formulation of your oil may have changed and it is more viscous at certain temperatures than before, even though it passes the specs for the oil weight.
|But why does the tapping stop when you slosh oil around? Is there a lot of oil left on top of the head, and sloshing it lubes the valve stems? Is the oil being pumped better from the sump pickup when sloshed because the pickup is clogged on the bottom? Is it an oil filter not being filled? Sounding similar to after an oil change makes this explanation seem likely. But solving the problem is beyond me.|
Or is the sloshing just in my head? Is it the varying revs of the engine making the tapping stop? Just trying to add to the thoughts here, I'm no expert.
Have you tried quickly pouring in a pint of oil while the engine is ticking over. If the noise goes away it would point to a blockage in the head supply. I blocked the oil spray holes in my rockers 20 years ago and it takes about 15 secs for the tappets to quieten. This has no effect on rocker or cam wear but I can run the engine with rocker cover off and trace a noisy tappet.
|Just a thought, but you might check if an end of one of the pushrods has come loose, and is moving up and down when the engine is running. Both ends of each pushrod are spot welded into the pushrod tubing, but they have been known to come loose.|
Curious if this still happens if you "pre-lube" the engine by running the starter untill presure comes up before turnning the key to allow ignition voltage to "start" the engine.
This is a starting proceedure I recall reading about several places including this BBS.
David 55 TF1500 #7427
Roger is right - this is common on T types and several of mine had come loose causing an illusive tapping. Strictly they need rewelding but centre punching has worked for me in the past Also more rarely the cup itself can touch the rocker in certain circs. which will be evident by leaving a mark - the cup can be turned down slightly to solve the problem.
Suggest you remove the cover for peace of mind - good luck,
|J C Mitchell|
|Roger and John,|
If the pushrod cup or end is loose, will the tapping cease when the oil supply is renewed up on top with running the engine? I ask, because I have that tapping on start up, and when I redid my engine I did not detect any loose pushrods... but I wasn't specifically looking either.
I noticed the tapping when adjusting the carbs with the bonnet propped up. I don't think the noise relates to oil feed, as 'tappet' noise can, but could be intermittent depending on revs, heat of engine etc. More importantly with the bonnet down and on the road the tapping is lost amongst all the other noise!
If in doubt I would check the pushrods although I don't think any harm results from the loose 'ends' over a short period. Also check the rim of the top cup as mentioned in my first note.
Good luck, John.
|J C Mitchell|
|Depending on the cam, you're going to have a little or a lot of tapping, mine is always worst when cold. Most of the Moss/Crane cams had around .019" and they are gonna rattle. We are too spoiled with our modern mechanical liftered things. I remeber dad's $500 Ford truck with the 292- now that thing tapped! George|
|hello, some thing occurred to me when i was on my last trip. if the tapping problem has not been solved, what are the groups thoughts that it may be piston slap? that problem initially presents the exact way this is described..tapping noise until the engine warms up. you can troubleshoot by pulling the spark plug wires one at a time and replacing each prior to removing the next. the tapping sound goes away if this is the problem when the corresponding spark plug wire is pulled. any thoughts? regards, tom|
|For David (Braun) - I cannot really give you a correct answer. I found some "loose" pushrods when I had the engine stripped for overhaul. I replaced them, but I did a lot of other work at the same time, including changing the camshaft. Thus although the engine was a lot quieter, without any tapping, I cannot really say what reduced the noise the most. I agree with Tom in that piston slap could cause the problem until the engine warms up, particularly with solid skirt pistons, or even split skirt pistons with a broken bottom ring. Could also be slightly over-advanced ignition, giving a problem until the engine warms up, but that would probably affect more than one piston.|
This is a troubleshooting list I copied years ago. It is generic, so you applies to the TD engine, except for the timing gears. We do have a timing chain which could give a different noise.
It is a little longish but seemed appropriate.
TROUBLESHOOTING ENGINE NOISES
A KNOCKING SOUND IN THE ENGINE IS MOST LIKELY CAUSED BY ONE OF THE FOLLOWING
1. PISTON SLAP: Makes a sharp metallic noise. Idle engine and short out each cylinder plug. The noise will disappear when plug with bad piston is shorted. Noise will also disappear at acceleration. This can be caused by worn or out of round cylinder, or broken piston ring. Correct problem by re-boring cylinder and/or replacing piston.
2. VALVE NOISE: Makes clicking or rattle noise. Caused by excessive wear on valve stem or lifter, out of adjustment, or stuck valve. Correct by adjusting valve clearance, replace worn valve or lifter, regrind cam, replace valve guide and /or valve. A stuck valve can sometimes be loosened by passing oil through the carburetor while engine is running.
3. ROD BEARING KNOCK: Makes sharp metallic noise similar to a piston slap. Detection is opposite of piston slap. Rod knock is not heard at idle. Knock becomes louder as engine speed is increased. Caused by excessive rod bearing clearance. Correct by adjusting rod bearing clearance to .0015 inches by removing shims. May require re-pouring rod bearing.
4. REAR MAIN BEARING KNOCK: Makes dull knocking or thud noise. Detected at speeds between 20 and 50 MPH. Knock will normally decrease or disappear while pulling or decelerating. Noise will be detected the loudest at normal driving speed, when not pulling or decelerating. Correct by adjusting bearing clearance to .001 to .0015 inches. If knock is excessive, crank should be checked for out of roundness. May need to re-pour all main bearings to correct.
5. TIMING GEAR KNOCK: usually the most difficult to diagnose. If gear is loose or badly worn it will knock in all ranges. Run engine slightly above idle speed. Slowly open and close throttle. Knock will continue to be present, but just as engine slows down knock will become a slight rattle. Remove timing pin and reinsert into timing hole on timing gear cover. Press timing pin tightly against timing gear and accelerate slightly above idle. Knock will significantly be reduced or disappear. Correct by replacing both timing gear and crank gear as a matched set. The two gears should have a backlash clearance of .003 to .004. If more than .009 inch backlash, an oversize (.005) timing gear should be installed.
6. WRIST PIN SLAP: This can not be detected by shorting out the cylinder plugs. Rapidly accelerate and decelerate the engine speed. The engine will pass through a certain speed range when the wrist pin will rattle at about the same pitch as a valve tappet noise. This can be corrected by installing a new wrist pin bushing in the rod or new wrist pin f badly worn. Wrist pin should fit the piston and connecting rod with a tight metal to metal fit. The pin can be pushed into the piston and rod with a slight pressure of the hand. Pin to rod clearance is .0003 to .0005 inches.
|D C Congleton|
Your description of the noise could just be valve clatter which is common with OHV engines and is most prominent with the engine cold. The clatter becomes less with warming up of the engine as the metal expanses a little and the distance between valvestem and rocker becomes smaller. It is not so much a problem with oil supply as there is always plenty in the head. As everything seems to work fine and oil pressure is good, I would not worry too much.
In the eighties there were sometimes only later cams available with tappetadjustment of .12. If adjusting to .19 as usual you get a lot more tappetnoise. A lot of XPAG engines were reconditioned then with the first hausse of TD interest.
Happy motoring and Christmas Greetings
|Frank van Geldern|
How is a Pin to rod clearance of .0003 to .0005 inches, measured?
|Gordon A. Clark|
|I don't know that us home mechanics could measure .0003 Gord, although a good machinist could. |
One method would be with a micrometer on the pin and, and an expanding gauge inside the piston bushing, and subtracting for the difference.
The method I always used to check for connecting rod pin (wrist pin) clearance is to check for a tight push of the piston pin with the thumb when installing. Then hold the piston and check for a slow decent of the rod from horizontal.
|D C Congleton|
This thread was discussed between 10/12/2008 and 22/12/2008
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