Trying to diagnose/describe a 240 noise

Hey all,

I'm at an impasse with my car and I figured I'd try see what you folks
(by far the best problem solvers for my Volvo) thought might be the
cause of my problem.

The car is a 1983 240 Turbo. It's an automatic with 3spd+OD (I am told
this was a common mod).

About a month ago I had the timing belt snap at very low speeds. The
car just died and, since I was going about 5km/hr I was able to coast
to the curb and wait for a tow. The belt was replaced and I was on the
road again. The day I got the car back I took it for an oil change
and decided to try something new: 20W50. Before you punce on this hear
my reasoning: the car temperature has been higher than normal (a
little higher every summer) and at one point on the third of several
consecutive really hot days the 10W30 seemed to completely break down,
registering low oil pressure even though the dipstick said it was ok.
After consulting the manual (and checking here) I decided to take a
shot at the 20W50 and put it in the day my car came back from the belt
replacement.

I mention this because I can't be sure which of these two factors is
causing "the noise".

The noise is best described as a METALLIC GARGLE, not unlike the sound
large trucks make. It comes in when the engine is under a load, either
uphill or accellerating. The sound comes in right when the Turbo boost
hits the yellow but if I push through that it goes away again and the
normal whine of the turbo spooling up can be heard. Also this sound is
coming from the back (or, I suppose, out of the exhaust). Also there
might be a little less power than before but things are otherwise
normal. If I can drive VERY conservatively I can avoid making this
noise most of the time.

One final tidbit: I have been topping up the oil with 10W30 as needed
and it has had some effect but has not completely eliminated the
noise.

My biggest fear: the Turbo bearings or some key engine component is
damaged either by thick oil or the snapped timing belt.
Ruled out: the exhaust has been thoroughly checked.

Any ideas?

Thanks in advance,
Boris
ps. Somewhat related: I got an antifreeze tester and it tells me what
temperature I will freeze/boil at. This seems completely disconnected
from the units specified in the manual...what range should I want to
see? How do I know whether to add water or antifreeze?

 

by blurp dropped his wrench, scratched his head and
mumbled,

This is common and is due to silicate build up in the radiator core,
either rod out, recore or replace the radiator.

There are two square cut o-rings on either end of the transfer tube from
the oil pump to the block. Some were misinstalled at the factory but all
harden over time and leak. Once the engine picks up speed the small leak
doesn't let the pressure drop to unreasonably low levels. The oil
pressure switch is set at 0,5 bar and is dead accurate. If you remove the
switch and install a test gauge you will indeed see pressure below 7.5
psi at idle, oil hot.

The exhaust can contact the body in several places, if one motor mount or
exhaust doughnut is broken or collapsed, a few more. If the cross under
pipe is cracked or a baffle has come loose in the muffler the exhaust
note will be affected.



Bob

 

Seems quite possible. Any idea how I would go about testing that or do
I just get them changed?

It also occurs to me that maybe a dyno would be a good place to test
theories and I may have access to one. I'll keep you informed and see
what else I can find out.

Thanks for your input!
blurp

 

Just thought I'd toss this out here in case anyone was experiencing
something simillar.

The "metallic gargle" has been identified by my brother-in-law as
"DETONATION". As soon as he heard it the sound it was the first word
out of his mouth. He described it as possibly also being linked to the
increased temperatures I had been seeing on the gauge (that is, the
higher temperatures would be contributing to the detonating).

His recommended remedy is to switch to higher octane fuel (I run Shell
Optimax which is 91 octane, he suggested Sunoco 94) and use an octane
booster next fill-up and then every now and again thereafter.

For the rising temperature issue he recommended a cooling system
flush. Now I have read on this group that radiator flushes on cars
this old were not recommended because scale broken loose could clog
the radiator up...any further thoughts on that?

Thanks to all who looked at this post and scratched their heads for
me. Now that DETONATION has been named does anyone else have comment
or suggestion? Anything else I should check or look into at this time?

Thanks for any new suggestions!

blurp.

ps. I'm reposting this with a new heading as well.

 

Doesn't detonation cause overheating? Could be your timing (spark) is too
advanced eg. it is at 10% BTDC and should be 15% BTDC. Those figures are
just example figures not the real ones. I don't have my Haynes on me atm.

Stuart.