That sickening feeling when you hear that sound. The drawn-out process of finding it and fixing it. And then fixing it again. Our friends at took a look at this all-too-familiar problem with older cars and wrote about it at the . It's reprinted here with their permission.
I think most classic car owners, especially those who do their own wrenching, at some point have very vivid visions of pushing their car off a cliff and
seeing it crash into the sea. You are eventually confronted with a problem or puzzle that gets the best of you and makes you question your love for this
Between the birth of our first kiddo and growing work and school obligations, I was forced to park my 1971 Volvo 1800E in the garage for nearly a year.
Finally, the time had come to pay some attention to the blue Volvo and get it back on the road.
Luckily, the old pushrod B20 fired back to life without much fiddling. I gave the car a quick scrub and took it for a shakedown cruise around the
neighborhood, hoping no stray police officers passed by and noticed my long-overdue inspection sticker. It's a great car. It's fun to drive and makes all
the right noises.
As I returned to the garage, however, I noticed a new sound coming from under the car when I depressed the clutch pedal - sort of a dull resonant
whirring/ringing noise that made me immediately think of bearing squeal or some kind of metal-on-metal .
"I hear a noise"
The car didn't make any alarming noises when I mothballed it months earlier. My first thoughts turned to what might have deteriorated as a result of
sitting for so long. The fact that the noise only appeared when I depressed the clutch pedal removed the transmission from the equation and suggested
something in the clutch assembly forward. The throwout bearing was the obvious culprit. The bearing had five years of hard use and could have been failing
when I parked the car. Extended periods of sitting, maybe exposure to moisture in the garage, had exacerbated the problem. Q.E.D.
Just to be sure, before I pulled the transmission, I put a few more miles on the car to see if the noise changed for the worse or (hopefully) just went
away once some heat cycling and use blew out the mechanical cobwebs. I parked it again and found that the noise was now present with the clutch in or out,
though depressing the clutch pedal had a very noticeable effect on the pitch of the noise.
The transmission in this car is a transplanted Borg Warner World Class T-5 instead of the original Volvo M41. The T-5 throwout bearing is designed to
always ride on the pressure plate fingers with a slight preload (unlike the stock Volvo setup, which has a spring to keep the throwout bearing from wearing
prematurely). This preload arrangement could possibly explain the presence of the noise with the clutch engaged or disengaged. To test this theory, I
adjusted the clutch cable to pull the throwout bearing away from the pressure plate and remove this slight preload. The noise was still present whether
engaged or disengaged.
In my mind, at this point, the only possible culprits were the throwout bearing or the pilot bearing, which would cost me about $40 in parts and a
depressing amount of labor. Without giving the problem much more thought, I decided to yank it all apart and just get it done - actually seeing the parts
should make diagnosis easier. It took me about three hours to pull the driveshaft and shifter, undo the mounts, tilt the engine, unhook the clutch, undo
all of the necessary bolts and slide the gearbox out of there.
I did a visual inspection of all of the parts. Nothing obvious jumped out at me. My full-faced organic performance clutch was worn, but still had some life
in it. It seemed to be wearing slightly unevenly to the outside, so I took the pressure plate to be skimmed at a local shop and did a lot of cleaning. The
throwout bearing appeared to be okay: no hanging as I spun it around, no signs of blueing or other damage. Same goes for the pilot bearing. I replaced the
throwout and it all went back together slowly with the help of my buddy Andrew over the course of an afternoon.
Fire it up - WHIRRRRRRRRR no change. The noise remained the same. So much for my throwout bearing diagnosis.
I took a video of the noise and sent it to my menagerie of trusted Volvo gurus to get ideas. I spent an hour with a stethoscope trying to pinpoint the
noise. It was most definitely loudest from the bellhousing. I then focused on describing the character of the noise:
1. It's a harmonic, resonant sound. It rings like a bell. It's not a grinding or crunching sound, but the sound of metal continuously dragging.
2. It is possibly bearing noise, but the only untouched bearings aft of the crank are in the transmission, which should not be in play with the clutch
3. The noise corresponds directly with engine speed.
4. The noise is not present when I first start the car. It only appears after about 30 seconds, which leads me to think there is a tight clearance
somewhere that only becomes an issue once the system sees some heat.
5. It's too loud to let it go and hope it works itself out (definitely something I considered).
It's got to be something simple - I started generating theories and testing them. I wrote stuff down. I sketched pictures on scrap paper trying to figure
out what I was missing. I thought about it while I walked the dog. I talked to my wife about it during dinner as she nodded patiently.
Things to check
1. Transmission input bearings? I played again with clutch adjustment. With the flywheel inspection cover off, I verified that there was no drag on the
clutch and the transmission was indeed not spinning at any time. I was relieved it couldn't be the gearbox, but I still spent some time verifying that the
end play of the transmission input shaft was in spec.
2. Something dynamic in the clutch/pressure plate/flywheel? I took the transmission out and started the car without it. No change. That removed the
throwout bearing, pilot bearing and anything aft in the drivetrain from the picture. That left me with something in the engine itself or something in the
flywheel or clutch assembly.
3. I hooked up a timing light to the coil wire so it would strobe twice per revolution. With the car running I shone the strobe on the flywheel looking for
wobble or runout or any other clue that something was wrong. I slowly turned the advance knob on the back of the timing light while watching the ring gear
slowly rotate in the strobe. Nothing, Nada. At no point was this flywheel making with metal on the back of the motor or the inside of the
bellhousing, and visual inspection of runout looked spot-on.
4. I removed the flywheel and clutch. The backside of the flywheel showed no signs of scoring or metal-on-metal . All bolts on the rear main seal
housing were seated and more than finger tight. Mating surfaces were clean and free of burrs.
5. Finally, I bought a dial caliper and tested crank thrust endplay. Seemed to be in spec. One theory was that this endplay was closing up after the engine
heated up and causing the crank to make with the thrust bearing. Depressing the clutch put forward pressure on the crank and could possibly be why
the sound changed the sound. I couldn't rule it out, but it seemed to be okay. I really didn't want to pull the engine. I just wanted to drive the car.
- Intermission -
I was stumped. I took all of the parts up to a local transmission shop for a second opinion. The manager spent 20 minutes with me talking through the
problem and inspecting the parts. He concluded that the pressure plate friction surface was slightly cupped and this was what caused the uneven wear on the
clutch, He advised that I replace both and have them rebalanced with my trick 8lb aluminum flywheel. He cautioned that aluminum flywheels can possibly warp
when subjected to intense heat from drag launches or too much feathering of the clutch around a track.
I bought a new clutch and pressure plate, balanced and installed a new friction surface on the flywheel. Machinist confirmed that the flywheel showed no
signs of abnormal wear, balanced fine and should be safe for use. I threw a Hail Mary and bolted it all back together. Turned the key, started the car, 30
seconds later WHIRRRRRRRRR the noise returned. %^$.
I didn't have many leads at this point without pulling the engine and opening it up to look for issues. I googled any keywords I could think of and talked
to a lot of people about the problem.
6. My friend Bob suggested checking the rear main seal. I inspected the rear main seal and it seemed to be fine - the spring that lives under the seal lip
had not walked out and the lip didn't look damaged. Outside visual inspection looked pretty concentric. Reluctant to break open the pan gasket or disturb a
non-leaking rear main seal, I dug out an old housing from my parts bin and fitted it up to an engine core I had lurking in the corner to see if it shed any
light on the matter. There is nothing internal to the housing that could be making , even if the seal was far off center.
7. I wondered if the sound was caused by built-up crankcase pressure pushing past the rear main seal and making a noise that I was confusing for metal
. I inspected the whole PCV system and did various checks with the motor running, putting my hand over the breathers to try and simulate pressure
build up. No change in the sound.
8. I removed the bellhousing, clutch and pressure plate. Using some old sockets, I made spacers for the starter bolts so that I reduced the moving parts to
the flywheel and starter. Started it up: no change. I found an old rusty stock 23lb flywheel in my parts bins. Bolted it up and started the car. NO NOISE.
It ran for 10 minutes and never generated the noise. This must be it! My aftermarket 8-1/2-pound aluminum flywheel was somehow the problem.
This was an important development and a massive red-herring. Was the greater mass of the stock flywheel absorbing the noise? Perhaps the noise was coming
from somewhere else and this greater mass was just masking the problem. To test the mass hypothesis I bolted the aluminum flywheel back to the crank and I
installed the pressure plate and clutch - this should have ended up being the same effective mass as the stock flywheel. Started it up, the noise was back.
Something about the flywheel that has nothing to do with mass was the problem.
I'd verified exhaustively that the aluminum flywheel was serviceable, balanced and had no runout issues. It was then, while working with the bellhousing
off that I noticed how close the ring gear of the aluminum flywheel came to the starter's bendix shaft. Switching back to the stock flywheel, I realized
that the aluminum flywheel had some different spacing, pushing the ring gear very close to the starter.
A new, even more absurd theory developed: I'd run this flywheel for six years with zero issues, but suddenly, for some reason, it was making with
this shaft. I spent an hour measuring and observing - it was a tight clearance, but it was definitely not making direct . Okay, perhaps this very
small airgap was creating a sound like a woodwind instrument. The stock flywheel didn't cause it because the ring gear was better positioned. Yes, this was
what I'd come to, this was the best explanation I could come up with.
9. I installed a spare starter. No change. There was very little room to shim the starter on this motor, but I was able to move the bendix shaft outboard
.040″. It seemed like this changed the character of the sound, and it delayed the start of the sound by a few seconds. That must be it, or maybe it
New Clutch and flywheel
10. I bought a new flywheel from TTV in England. The dimensions looked spot on and it was a single piece of sexy billet steel. Shipped to my door for $480.
I bolted it up and it was much closer to the stock flywheel's dimensions - it was time to test my ridiculous "Singing Air Gap" hypothesis. Started the car,
a minute went by, I started to smile and thought about all of the cold beer I've earned - then WHIRRRRRRR the noise started.
This was the moment when I could most clearly envision pushing my car over a cliff and into the sea.
I could think of no other source of the sound. A couple of months and a load of expensive parts had led to no resolution. Convinced that I'd reached the
end of my resourceful diagnostics, I was resigned that it was an issue with crank thrust and that the motor would have to come out to get to the bottom of
it. At that point, I was no longer hesitant to screw up the pan gasket by pulling the rear seal housing - it was worth checking for anything obviously
amiss around the rear main bearing cap.
As I wrenched on the bolts, I found that they didn't seem as tight as I would have liked them to be… Snug, but not with much clamping force. I
removed a bolt and I didn't see any threadlocker residue on the threads. I must have skipped it when I put this motor together eight years ago. A previous
I removed the aluminum housing and looked all around the seal lip. With it off, I could tell it hadn't been an entirely concentric seal. The bottom of the
seal was slightly more deformed than the top. It was also a totally different casting from the spare stock housing I'd inspected earlier. Three
cast-aluminum ears protruded into this seal opening that were not present on my old B20 seal housing. Some asking around revealed that this is the housing
for a later motor. These housings are technically interchangeable among all Volvo 4 cylinder engines between B18 and B230 but they do have slightly
different castings. You can tell in this photo that these aluminum ears are slightly polished from where they've made gentle with the crank.
Immediately, I flushed the oil and reinstalled my spare housing with the old felt seal. I bolted the flywheel and starter up - Crank, wait, wait, wait - no
noise. That was it. I can say with confidence what caused the noise. The rear main seal housing had walked slightly up the back of the engine and brought
these 'fingers' in with the rear crank surface.
A friend mailed me a spare B20 housing machined to accept the $3 poly seal. I pressed it in and bolted it all back together for the third time, with
Andrew's help. No noise, smooth gear changes, problem solved. Finally the car was back on the road.
Clutch and pressure plate: $649
Billet flywheel: $480
Pilot bearing: $14
HD throwout bearing: $26
3 quarts of synthetic trans fluid: $30
Polyurethane rear main seal: $3
Red threadlocker: $4.
$1,206 and a lot of my time. A better mechanic could have diagnosed and solved it for $20 in parts. The upside is that I am now that better mechanic.