MTFCA Forum

I know it's impossible to describe, let alone diagnose strange engine noises on a forum like this, but I'm looking for some general guidance. If my description of the noise problem sounds similar to someone's previous experience I would appreciate the feedback. (I didn't build the engine I'm describing, but it was newly rebuilt several years ago and sitting in the previous owners shop).

Started the engine for the first time yesterday and immediately heard a steady rumbling, growling sound that resembled growling gears or a very notchy/bad ball bearing and seemed to come from the front of the engine - possibly in the generator area or the camshaft?

My first thought was to remove the generator and make a plate to cover the hole, start it again and see if the noise went away. Other than that, should I be concerned about excessive camshaft runout & possibly getting into the timing cover?

Thanks in advance for any thoughts or ideas of where to start looking for the trouble.

Mike in Texas

Fiber timing gear doing what fiber timing gears do?

Thanks, Steve. You may be on to something. Since I didn't rebuild the engine, I didn't check the timing gear to see if it was fiber or aluminum. I'll pull the generator to make sure.

Mike sounds similar in nature as a possible reground camshaft with an improper front cam bearing.

Hope this Helps,

Hank

If the timing gear was shattered like that, the engine would not run at all because the synchronization of the opening and closing of the valves to the motion of the pistons would be thrown off. Though the steel timing gear is noisier than a fiber gear, I have always preferred steel to the fiber gear for the reason you see in the photo. Jim Patrick

Mike. Give Ross Lilleker a call. " Mr Model T" in College Station. 979-218-4083. He has probably heard ever strange sound a model t can make.
Good Luck

Great pointers from everyone. Anyone ever heard of a generator making the noise described?

Yes. One thing to look for, that I discovered on my ‘26 coupe, when I first bought it in 1970 is that the original gear on the original generator wore the gear hole, pin and gear key and the generator shaft causing the gear to loosened over the years so that the gear wobbled and did not mesh properly with the timing gear, which created a lot of noise. When I replaced the original generator gear and timing gear set with a new set, it quieted it down, substantially. When you replace one gear you should replace both, as an old worn gear will not mesh properly with a new gear. Jim Patrick

Very noteworthy, Jim. I'll check it out!

Yeah, my first choice would be generator. Could be a bad generator or a too-closely positioned generator. Sometimes you need to shim the generator mount casting out to get proper gear mesh, particularly if an oversized cam gear is used to make up for a worn crank gear. Doesn't need to be fancy plate, just get the thing out, cover it with anything and start it up. You'll know instantly if you've found it.

One other thing is if the generator is not hooked to a battery OR grounded. It will howl until it dies a hot smouldering death.

Could be the transmission making that sound. I put one together in my 21 Touring rebuild and used what I thought was a good low speed drum. I installed new triple gear bushings and the drums were rebushed. Stated it up and it ran fine but with a low growling sound. Driving it was fine but the sound was a little louder. After much head scratching and checking I decided to pull the engine and checked the transmission again and I had purchased another low speed drum, put it back together and after starting it the grumbling sound was gone.
I read other forum posts and others had the same issue especially when using good used trans drums. Not real common but it happened to me. Also read that eventually the gears and drums would ‘wear in’ after a while especially when using used triple gears and drums that came from other transmissions.
Opinions will differ of course.

Awesome stuff guys...thanks!

My vote is a generator with a slightly bent front shaft.

Pull the genny... of the noise is still there try to “feel” some backlash in the cam gear thru the genny hole. Timing gears could be howling if too tight...?

How many gaskets do you have between the block and the generator mounting bracket? The gear mesh is probably too tight making that noise so I would add one or two gaskets more to bring that bracket outward a little bit.,.
... Giving some room for those two gears to work together.. had somewhere noise on my 26 runabout and I did run with a blanking plate and no generator for a while and the engine was a lot quieter. I ended up adding two more mounting gaskets at the block and no more noise.

I have my fingers crossed that the generator is the problem. Sure don't want to have to pull the engine to look for hidden gremlins in the transmission...or elsewhere!

Also hope it’s just a generator problem and nothing more than that. T engine noises are sometimes are hard to identify because the engine and transmission are together in the same pan and the noises seem to run together.
Good luck.

If removing the generator does not improve the situation, it would pay to check the depth of mesh on the timing gears. It does not take much of an error setting the camshaft to crankshaft distance when boring the main bearings to have them too close in mesh and the timing gear bottoming out in the crankshaft gear. This condition can be alleviated by machining a little off the large timing gear.

Allan from down under.

As our own Steve Jelf has so eloquently stated..."the inevitable often happens". Removed the generator last night, started her up, and made the grim discovery that the noise was still there. Before I do the engine extraction, I'm going to check the cam gear mesh as Alan has mentioned and remove the starter and do some more snooping around to see if possibly the starter might be dragging on something. What else could it be??

Are you getting oil to the front of the engine? The oil line runs from the rear of the block between the flywheel and ends behind the cam gear. If that line was not installed or if it is blocked, you will not get oil to the timing gears and also the babbit main and rod bearings will not get oil. So be sure it is installed and clear.
Norm

Norm, I feel pretty sure the oil line is open, but I'll check it before pulling the engine.

I’ve seen many poor quality aluminum cam gears over the past decade. Most of them were not machined all over (rough casting visible in the disc area where it didn’t require a good finish). Some of these gears had up to .007” indicator runout and some were okay. A cam gear with runout that binds the front cam gear once per revolution could be the issue.

Adam, thanks for weighing in. Best I can tell, the cam gear is fiber so I think the problem lurks in the transmission area.

Best I can tell, the cam gear is fiber so I think the problem lurks in the transmission area.

What?!?!?!

Do a little more sleuthing before you do anything major, like haul the engine out. Try removing the pan & transmission inspection covers and the spark plugs. Then have someone crank the engine over by hand while you look inside of the pan and the transmission. Look & listen for anything odd. Look for fore & aft movement of the camshaft. See if the front cam lobe isn't snagging the back of the front cam bearing. Try to determine if the timing gear has any backlash, or way too much backlash, (should be about .005").

I think I also noticed that you haven't had many posts on this forum. If that means you're new to Model T's, then I have to ask, do you realize that T transmissions are by their nature, fairly noisy? Maybe not all of them, but most are... Determining the difference between bad noise and normal noise comes with experience.

Steve Jelf wrote: ↑

Tue Apr 07, 2020 10:37 am

Best I can tell, the cam gear is fiber so I think the problem lurks in the transmission area.

What?!?!?!

I think he means that he's ruled out timing gear noise based on the fact that it's fiber, and has moved on to suspecting the transmission.

5.00 tool from harbor freight that every t owner should own, often saves hours of chasing gremlins.

Is the oil line working? Pull the passenger/front inspecion pan bolt and start car. If oil flows, it's working.
Is it the transmission/gears? Jack the car up, blocked well, put in high gear with engine running. Howling go away then it's transmission problem.
Still howling? Pull radiator and timing cover and try to feed a slip of paper into the gears as engine is turned over. Locks up? You've found your problem.

If it's gears, you can't fix a too-closely-meshed gear by simply reducing the OD...the pitch diameter is too close. Dan McEachern makes very nice gears standard, undersize, oversize, and 7 1/2 degree advanced. Now, you may get a tight gear set to run QUIETER by trimming the OD in your lathe, but you are really fixing nothing, only aleviating a symptom

All comments above are great and certainly worthy of closer inspection. I'll be looking into all of them before swinging the motor. Back later with more details.

NOISE UPDATE!-----got the starter out last night and found this: The balance ring counterweight is completely missing from the Bendix gear! Without the ring I suppose it caused the spring to bind up and deform. The distorted spring must be dragging against the flywheel and making that awful sawing noise. I'll know more when I can replace the Bendix and try to run her again.

Whoa!! Your not seriously think of running that poor engine with loose-missing parts floating around in it, are you? You are sitting on a bomb. Please think of all the could go wrong.

Well me thinks you found some or all your noise. But it not the spring rubbing on the flyweight. It is the missing counter weight being chewed up in side the engine. Don’t start the engine until you find the remains of the counterweights.

Yep, I already probed around inside with a magnet pick-up tool for the missing ring, but came up with nothing. My next move is to buy or borrow a video inspection camera and do some serious snooping. I'm not sure if it's possible for it to come of the end of the starter with the Bendix spring in the way. My first thought was that the previous owner installed it that way not knowing it was missing. We'll see...

did you take the bendix off BEFORE removing the starter?

Scott, yes absolutely! I've read of the disaster that ensues when not removing it first. I will say that the flywheel magnets and coils had been removed (we're running a distributor) and oil slingers were installed, but I removed the Bendix anyway as a precaution.

If you can find the person who installed the starter, ask if he remembers whether that weight was in place. It is almost impossible for that part to come off if the spring was still bolted in place. If you can't find out whether it was in place when the starter was installed, you should remove the hogs head, drain out all the oil, and turn the engine a little at a time with the crank until you can inspect all the magnets for pieces of metal which might be stuck to the magnets. Then thoroughly inspect inside the crankcase and use a magnetic wand to retrieve any loose parts. You should also inspect each magnet to be sure the keepers are in place with the brass screws. As you turn the engine, you can also notice whether it turns smoothly without a catch. Any loose steel part will either drop to the sump at the bottom of the crankcase, or be stuck to the magnets. Note the magneto ring near the starter location. How is the insulation? If it is pulled off or the coils bent, you will need to replace the coil ring. To do this would require pulling the engine. Note, when either installing or replacing the starter, the shaft should be put through the hole first and the starter bolted in place. Then after the starter is in place, install the bendix.
Norm

Norman,
No coils, no magnets...see my previous post. I agree with you - it's hard to imagine that the counterweight ring could possibly come off with the Bendix spring and bolts in the way, but stranger things have happened! I"ll still be checking around inside looking for the errant part.

mgarrett wrote: ↑

Thu Apr 09, 2020 10:27 am

Norman,
No coils, no magnets...see my previous post. I agree with you - it's hard to imagine that the counterweight ring could possibly come off with the Bendix spring and bolts in the way, but stranger things have happened! I"ll still be checking around inside looking for the errant part.

I agree that the counter weight would have a very hard time getting past the spring, unless it broke in two. Not totally impossible I suppose. Have a look at the oil slingers while you've got the starter out. Wouldn't be the first time that an oil slinger came off and made a mess. Just another thing to cross off the list... hopefully.

Another thought, the counter balance ring is also what keeps the starter gear from drifting back into the ring gear. That's what the little spring loaded plunger does. Do you suppose that your noise has been the bendix gear running into & rubbing against the ring gear? That would make a racket.

Jerry,
I think you're on the right track about the bendix gear rubbing against the ring gear. There is a lot of slop without that balance ring being in place and it's bound to allow for parts to come into contact with each other that shouldn't be. Also, when I spin the engine over with the hand crank and the starter removed, I don't hear any sawing or growling.

I had a counterweight break in half and fall into the sump. The ring gear picked up one half and jammed it between the gear and the side of the pan. Had to pull the hogs head to get the jammed half out and fish out the other half. Luckily this happened while starting.

Hey John,
That's unfortunate, and I appreciate you sharing your experience. I'll be especially vigilant to use my inspection camera snake to look into the belly of the beast in case the same fate befall me!!

The distortion of that Bendix spring is likely due to the fact that it is the wrong spring for a T model. Looking at the end of a T Bendix spring, it is coiled anti-clockwise. Yours is wound clockwise.

Allan from down under.

Thanks Allan, I hadn't noticed being preoccupied with chasing the source of the noise.

You mentioned in the beginning that the engine was newly rebuilt several years ago.

The only way the balance ring could get loose and is inside the engine is if it was broken in half, which is possible, but generally unlikely. It can happen if someone steps on the starter when the engine is at speed. In this case it generally causes instant catastrophic damage.

What seems more likely is that bendix was assembled and put in like it is.

If this is the case, then I would be real skeptical about the quality of anything else inside that engine.

It might be time to make a decision about whether to fix the one thing currently known to be wrong with it and take a chance that it is the only existing fault, or to pull the engine, remove the hogshead, pan, do some good inspections, check bearings, etc for piece-of-mind that no other failures are imminent.

Taking the whole engine apart could also depend on who assembled the whole engine. How much was done by the shop and how much was done by the customer. Could have been just a short block and assembled by customer or even if whole engine was done, customer could still have installed the starter generator etc.

So many engines from "estates" with no bill of sale or parts list or invoice from a reputable builder turn out like this...

When the car/engine is not known by other hobbiests it is usually because the original owner did everything on their own because everyone knows "if a blacksmith could fix these cars, I sure can", and they do. Sometimes you get lucky, but most often they have more than usual teething problems.

Adam is absolutely right...I didn't want to be the one that mentioned it first.

I suggested this before and I will again. Get a length of magnet from an old refrigerator door seal, it is inside the rubber, and use it to probe. I found that it will lay flat on the crankcase and you can push it to cover almost all the inside. Has worked for me and several others. Just my .02. Dick C.

I purchased one of those digital inspection cameras over the weekend with the long goose-neck probe and, going in from the starter opening, snooped around; got a good look at the oil baffle above the drain plug and as much of the oil pan area as I could get to and found no sign of any broken pieces of the balance ring. (Confession: since I installed this engine in the frame about 2 years ago and the starter came with the car, I must have absentmindedly installed the starter and bendix without noticing any problems with the missing balance ring - so bad on me!) On that note, I also want to thank Alan from Down Under for correctly pointing out that the spring on the bendix was incorrect: wound clockwise instead of counter clockwise - never knew there was a difference!

The bottom line:
Installed the starter with the correct bendix & spring and, voila! NO MORE NOISE! The engine starts and runs great. Just have a few oil leaks to correct and we should be ready for a shakedown run.

Many thanks to all who chimed in as all advice was certainly welcome.

And that my friends is what solid diagnosing is all about. Don't jump in and tear it up. Ask questions. Congratulation on a job well done.

That's very good news!
Norm

Good to hear! Another lesson in checking the easiest and obvious first. Better than pulling the engine, pulling apart and then find it was the starter bendix to begin with! Those engine sounds can fool you for sure.