308 engine noises

Hello all- more questions:

84 Euro QV
I drove the car to Limerock this weekend (about 5 hours each way- it was a blast) and noticed a strange rhythmic sound when I got there. I know sounds are hard to describe- but here goes:

It seems to be a high pitched kind of "whum, whum, whum, etc" every 1/4 second or so at idle.
The sound goes away while reving- or I just can't hear it any more. Slowly reving the car and it does not seem to change frequency- stays every 1/4 sec or so until it dissapears under the other sounds. Turned on a/c- no change. Push in clutch- very slight change in pitch. Throw-out bearing? Seems to be coming from the left side of the engine. Darin from Boston Sportscar Co. was around, who has looked at the car in the past; and he couldn't figure it out without really diving in. He even called on Sunday to make sure everything went o.k. Thanks for all the help Darin!

So I got his cell# in case something happened, and left for Maine. No problems (temps, pressure) on the way home- just the noise remained. No change in the noise. The car has normal power, exhaust note, etc.

I know this is a difficult question to answer- but does anyone have any ideas? I will probably have the car flat-bedded down to Boston Sportscar so they can take a look and repair.

Thanks in advance.

Noises are hard to guess at.

A Very common source of 'strange noises' on 308's is exhaust leaks at or near the heads, either from the EGR Valves which are prone to rust out, cracked/broken EGR Hoses which harden and crack, or the Air Injectors, Exhaust Test Pipe Fittings.

T/O Bearing noises aren't really uncommon, but present no short term problem in the vast majority of cases.

If the trans is low on oil I have heard rythmic noises from the transfer gears on occasion.

Best way to pinpoint & isolate drive train noises is with a Mechanics Stetoscope.

HTH's

Regards, JRV

Thanks JRV.
The shifter seal is slowly leaking, (and maybe pan nuts) so maybe the trans oil is low- I will just replace.

Speaking of transmission oil- what do you reccomend for my car? Something I can buy at NAPA, Autozone, etc. would be best- if possible.

Also- can you fill the diff through the clutch housing filler hole or do you have to fill in two places- one with .17 pints of oil?!!

Thanks again for the help.

Hi John,

The OM states to use 80-90 wieght, what they neglect to mention is that Grade GL-5 is neccesary and some Lmtd Slip Diff Additive is helpful in prolonging Diff life. I use Castrol here in the shop, however you could likely find a good oil in a local store.

IMO, the trans should be filled first and then the transfer gear housing. This insures no mis-understandings (failure to guess volume accurately) that could be costly to remedy.

Regards, JRV

JRV-
A follow-up.
I changed out the trans oil this weekend- no change in the sound.
I started the car for a couple minutes before changing the fluid- no sound. After fluid replaced- test drive (no sound at first). About five or ten minutes into drive- the noise reappears.

Also- for the first time ever- the car did not fire up after a few revolutions when cold. This was immediately after trans fluid change. It turned over for five or six seconds- no fire. Tried again after a few seconds with slight pedal- it fires up. Strange.

I listened around with a tube and could not isolate better than driver side of the engine.
Fuel pump? The noise doesn't seem to change with the rpm's of the engine as it revs- but does slow it's interval as the car is slowing rpm on shut-down. I think I just can't hear it as it revs up.

Thanks JRV

I still think there is a good probability the noise is exhaust related. There are quite a few exhaust pieces on the right side. What makes me think this is the rythmic atribute of the noise, at least if I'm understanding the explanation that is..

On the engines right side you have all the EGR valves and hoses that carry exhaust gas. If one of these components develops a leak or a crack they will make a rythmic noise, also the same is true of the air injector tubes and exhaust gas Testing tubes.

Try looking at those areas & components .

HTH's

Thanks again JRV- I hate to keep bothering you.

Which of these things you mentioned are not applicable because of the car being a Euro?
No air injectors, test tubes etc?

I bought a stethascope and poked aroud anywhere I could reach with it. The only place I got any of the noise through the scope was on the plate below the oil filter that accesses the clutch/flywheel. The fuel pump, water pump, alt.,
timing belts, a/c, oil cooler, heads, intake, transfer case, were all quite- at least I couldn't make out any of the noise.

Again yesterday, the car did not make the noise until I drove it for about five minutes. I even let it warm until the fans came on before driving it- and the noise did not appear. Once driven for five, it returns. Could the clutch, or TO bearing make a noise like this?

Thanks for all the info.

Hi John,

On a Euro version some of the exhaust parts mentioned might be missing but most should still be there.

To answer your question, yes the T/O Bearing can make a rythmic noise after the car is in use for awhile, and so can the transfer gears and/or bearings. Most T/O noises can be changed by pushing in & out on the clutch peddle, which usualy helps determine if that's the source of the noise as the sound will change or come & go.

Try the peddle routine to see if it has any effect on the noise.

Clutch pedal movement does not change the sound- so the throw-out bearing must likely be o.k.

I'm going to listen more with the stethascope from underneath and see what I can find. It seems like if I keep listening to the thing long enough with the scope- sooner or later I will find it.

You wrote the the EGR is on the right side of the motor? Is this the passsenger side? Do Euro's even have an EGR valve? I couldn't find one.

The sound is definately coming from the left/driver side, although I've been listening to anything the scope will reach.

Thanks again.

Sorry John, I meant left/Drivers Side.

For exhaust leaks the noises are more easily picked up with the stethescope by removing the tip and just using the hollow tube.