View Full Version : TR2/3/3A TR3 Engine Noise

02-16-2010, 03:47 PM
Aloha All,

The engine in my TR3 has recently developed a rhythmic knocking noise, like rapping a knuckle on a hollow core door. So my initial thoughts are that I have a bad connection rod bearing or main bearing. If the engine is cold, the noise is not apparent but appears as the engine warms up. Listening with a mechanic's stethoscope I really can't hear any knock. I spent the weekend checking nuts and bolts to make sure it wasn't a door or hinge making the noise.

Before I tear down the engine are there any other things to check or possibilities that might make this noise?

02-16-2010, 03:52 PM
Did you try removing the belt to make sure it's not something external?

Geo Hahn
02-16-2010, 03:57 PM
Can you get a feel how the rhythm relates to the engine... i.e. once per revolution or once every other revolution? Sounds deeper than a valve noise (which would be one of the every other rev' noises) but still I would check valve lash just because it is quick and simple to do.

I would also put the stethoscope against the water pump, distributor, generator, etc... things that can go bump in the engine.

02-16-2010, 04:56 PM
Thanks guys, I didn't remove the belt but that would eliminate and isolate some possible sources of the noise.

I did check valve lash and #8 was very tight, less than .009 so I opened that up, but all others were in the .010 - .011 range hot. I did check with the stethoscope the cam shaft, valve cover, generator, water pump and distributor with out hearing anything strange. What I hear a whirring sound.

The noise is audible about once a second or perhaps less at engine idle (about 650-700 RPM) so seems much less than every or even every other engine rev.

02-16-2010, 06:14 PM
A rod knock will get louder under load on acceleration or deceleration.
The point between acceleration and deceleration will minimize a rod knock.
main bearings as a rule will not knock unless they are really really bad, and then it is the same scenario as a bad rod bearing plus lousy oil pressure especially at operating temperature. Wrist pins, broken, cracked pistons can also knock, again the acceleration deceleration rules apply.
Valve train problems {knocking} are higher pitched than lower end knocking as a rule.
Pulling a plug wire while running {one at a time} can indicate which cylinder has the problem {rods and mains}. With the plug wire off the knock will minimize or completely go away. while a valve noise will remain.

Just my observations of 40+ years of shade tree mechanicing
and what I learned from my father, a professional mechanic of well over 60 years.

I hope this helps you sort it out.

02-17-2010, 02:37 PM
Dave you commented that you hear a whirling sound. Are you sure that the noise is not coming from the clutch? You might want to look in through that cheese little inspection plate and see if anything wants to fall out-just a thought. The whirling noise could also be the timing chain tensioner or perhaps the chain hitting the cover.

02-17-2010, 08:25 PM
The noise is audible about once a second or perhaps less at engine idle (about 650-700 RPM) so seems much less than every or even every other engine rev. Makes it unlikely to be inside the engine, IMO, especially if you couldn't hear it with your stethoscope. Any kind of bearing knock will be loud through a stethoscope anywhere on the engine, only loudER near the bad bearing.

I'd keep looking for an external problem, like perhaps the exhaust hitting the frame. Does pressing the clutch pedal make any difference ?

FWIW, one of my former TR3A engines had a problem where it would knock 3 or 4 times in rapid succession, only at hot idle, and then be quiet. Never did tear it down to discover the problem (wound up selling the car instead), but it ran that way for a long time without seeming to get any worse.

02-17-2010, 09:00 PM

Thanks Kerry, Steve and Randall. All good ideas to help isolate or eliminate sources of noise. I think this weekend I will follow all these suggestions and also unload the boot, glove box and door pockets. Hopefully I can report back it wasn't an internal engine problem.

02-17-2010, 09:43 PM
Maybe lift off the valve cover and inspect the valve train.

02-17-2010, 10:38 PM
I once had a mysterious knocking noise on my TR3. Sounded like a misadjusted valve.It turned out to be the "keyway" inside the fan pulley had worn to about 3" wide creating the noise. Check to see if you can turn the pulley back and forth.

02-19-2010, 07:25 AM
TR camshafts sometimes develop a clunking noise which is most likely end float, but they keep on keeping on, like the hardy souls they are.

I know a TR3A that had that noise for at least 12 years, and it was driven like a getaway car, but never missed a beat.

Sadly it outlasted its owner, my closest TR mate in Australia.


02-19-2010, 08:27 PM
Some good suggestions here that should be checked before engine tear down.
I had a GMC jimmy years ago with the 350 motor that developed piston slap on one cylinder. I isolated it by pulling off the spark plugs one at a time till I got it; then pulled the head, dropped the pan and popped out the piston. The offending piston was well scored and worn but the bore was perfect, knocked off the glaze and replaced it with a single new one and drove the truck for another 5 years; never did figure out why one piston went bad, probably lost a ring and it went worse from there.

02-20-2010, 02:00 PM
Thanks for all the suggestions. My son and I are going to see if we can track down the noise today. I hope to report back we had a successful hunt.

02-20-2010, 02:50 PM
I have a 60 TR3A and it makes a noise similar to yours. I replaced the engine because of the noise. Thought it was rod bearings. After a little while the new engine made the same noise. I did use all the old engine parts like the cam, head, water pump and so on. Not the crank, rods and pistons.
I'll keep up with this post to see if anyone comes up with a good possible cause.

02-20-2010, 06:32 PM
I'll bet it's the fan pulley.

02-20-2010, 10:14 PM
We checked the rocker assembly and push rods and did not find anything unusual. With spark plugs removed and rocker assembly removed spinning the engine with the starter did produce the knocking noise. The spark plug on #3 cylinder had a damaged ceramic insulator around the center wire. It was not damaged last week when I adjusted the rocker arms. With the fan belt removed the niose remained, so that should eliminate the generator and water pump. The fan and pulley were not loose. Using the stethescope the noise ( a tapping sound) seems to be loudest on the external housing of theoil pump.

02-20-2010, 11:57 PM
I have seen broken generator mounts cause a weird knock...eleminate the easy to fix stuff first!!
MD(mad dog)

02-21-2010, 01:28 AM
With spark plugs removed and rocker assembly removed spinning the engine with the starter did produce the knocking noise.

You have the belt removed, and rocker assembly removed and you are using the starter to turn it over and the noise is always there?

Can you tell if the noise is made once per revolution or once every other revolution? Someone correct me if I'm wrong, but the crank rotates twice for a single rotation of the cam. Maybe a valve tappet is sticking?

02-21-2010, 08:27 AM
Piston slap? Wouldn't that come and go?

02-21-2010, 03:42 PM
Broken piston.
If he broke the plug insulator, bets are the rings broke, came through the top land, and impacted the plug.

02-22-2010, 02:08 PM
Piston slap can come and go. Heat decreases the cylinder OD tightening the clearances.
Also, if you are concerned it might be rod bearing clearances then use 50 weight oil and see if the niose clears up.

02-24-2010, 05:53 PM
Hi Dave I just thought I would throw this out. Many years ago I had a tr3 problem that was a knocking noise close to where you described and it turn out to be the inner rod of the steering column. Please keep us posted because personally I enjoy diagnosing knocking noises from thousand mile off.

02-24-2010, 07:13 PM
To me, experientially, the key piece is the broken insulator on the sparking plug.

"The spark plug on #3 cylinder had a damaged ceramic insulator around the center wire."

Now, too much side load with the socket and you can do that, or, something floating around in the comustion chamber, like a screw out of the butterfly shaft, a bolt from the air cleaner, or, a ring that broke and worked up through the top land.
It may now be wedged (or part of it) in the top of the piston, contacting the bottom of the head.

I've got a bore light, if you are careful, with piston down, semi-dark shop, you can see the top of most of the piston.


02-24-2010, 07:28 PM
I agree that the broken plug is very concerning.

I also agree it's fun to diagnose from 1,000 miles away -especially when it's not my car!

But, the suspence is killing me. Dave has been quiet and I hope it means he's figured it out and is out driving around, but my thoughts are elsewhere. You could always clean out your shop-vac and see if you can vacuum anything out of the plug hole. I think if it were wedged into the top of the piston, the noise would stop.

02-24-2010, 07:56 PM
Not if it's a big enuff piece to hit th' roof of th' chamber.

But due to the description as a more syncopated noise I'm leanin' to th' damper keyway.

02-24-2010, 08:02 PM
Pull the plug and run a magnet through it.

02-24-2010, 08:36 PM
If it's wedged into the piston, that won't help.