740 spark plug replacement

  • Thread starter Thread starter Mungo \two sheds\ Toadfoot
  • Start date Start date
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Mungo \two sheds\ Toadfoot

It might be common knowledge but I thought I'd share anyway...

I bought some new Bosch spark plugs for my 1989 2.3l 740 and three of the
old plugs came out with hardly a problem, the fourth though, in number three
cylinder, was tighter than a tight thing which had been tightened by
Mr.Universe's big brother.

I was able to undo it only about half a turn, then tighten it, then loosen
it, then tighten it..... I sprayed penetrating oil on it several times but
still only got it loosened about one whole turn in all before it locked
solid again. Becoming more and more worried about stripping the thread I
consulted the source of all knowledge - the internet - and found that
running the engine for just a couple of minutes should expand the
alumin(i)um head sufficently to give slightly more space for the plug to be
unscrewed, and.....it worked!!

There are few occasions in life when one is truly happy but this was one of
them. I've taken many engines apart in the past so I knew what would have
been involved if the plug thread had stripped.

Si
 
Mungo said:
It might be common knowledge but I thought I'd share anyway...

I bought some new Bosch spark plugs for my 1989 2.3l 740 and three of the
old plugs came out with hardly a problem, the fourth though, in number three
cylinder, was tighter than a tight thing which had been tightened by
Mr.Universe's big brother.

I was able to undo it only about half a turn, then tighten it, then loosen
it, then tighten it..... I sprayed penetrating oil on it several times but
still only got it loosened about one whole turn in all before it locked
solid again. Becoming more and more worried about stripping the thread I
consulted the source of all knowledge - the internet - and found that
running the engine for just a couple of minutes should expand the
alumin(i)um head sufficently to give slightly more space for the plug to be
unscrewed, and.....it worked!!

There are few occasions in life when one is truly happy but this was one of
them. I've taken many engines apart in the past so I knew what would have
been involved if the plug thread had stripped.

Si
Click to expand...
Good job.
I'd have probably stripped it or broke it off before thinking about
checking on line. ('cause I know *lots* about motors and stuff... I
think to myself.)
Don't forget the anti-seize on the new plugs.

A funny story:
My neighbor bought a new model year Honda back in the '80's. He went to
change the oil and couldn't get the filter off. He ended up shreading
the canister all the way down to the flange so there was nothing left to
grab and turn.
He asked me to bring my welder over and weld something on the flange so
he could turn it. After I welded a little bar on it, it spun off by
hand... the heat from welding had softened the gasket.
BTW... the filter he bought to replace it was the wrong one and it seems
the correct filter was a new design and back ordered from Japan. He
waited a week or two before he got the replacement.
 
Clay said:
Good job.
I'd have probably stripped it or broke it off before thinking about
checking on line. ('cause I know *lots* about motors and stuff... I
think to myself.)
Don't forget the anti-seize on the new plugs.
Click to expand...

It's another good reason not to use air tools to remove or replace
spark plugs!


__ __
Randy & \ \/ /alerie's
\__/olvos
'90 245 Estate - '93 965 Estate
"Shelby" & "Kate"
 
Mungo "two sheds" Toadfoot said:
It might be common knowledge but I thought I'd share anyway...

I bought some new Bosch spark plugs for my 1989 2.3l 740 and three of the
old plugs came out with hardly a problem, the fourth though, in number
three cylinder, was tighter than a tight thing which had been tightened by
Mr.Universe's big brother.

I was able to undo it only about half a turn, then tighten it, then loosen
it, then tighten it..... I sprayed penetrating oil on it several times but
still only got it loosened about one whole turn in all before it locked
solid again. Becoming more and more worried about stripping the thread I
consulted the source of all knowledge - the internet - and found that
running the engine for just a couple of minutes should expand the
alumin(i)um head sufficently to give slightly more space for the plug to
be unscrewed, and.....it worked!!

There are few occasions in life when one is truly happy but this was one
of them. I've taken many engines apart in the past so I knew what would
have been involved if the plug thread had stripped.

Si
Click to expand...
Another trick for the mental toolbox. Thanks! (And maybe more thanks down
the road when I need to use this.)

Mike
 
I have had many cars with aluminium head and never had success with bosch
plugs .I use anti seize because of my experience with bosch .I prefer NGK
plugs because of this very reason .As this is over many cars and millions of
miles it pays .Motor craft were good till they stopped making them in Japan
..
 
ALWAYS use anti-seize when plugs go into an alloy head.

Your plug problem may have been caused by either the Bosch plugs beign
just a little longer than othre brands in th threads, or they might
have run just a bit cooler (or both) causing excessive carbon build up
making them difficult to get out....?

I see commercials for "Denso" spark plugs. I am assuming that this is
the renamed "Nippon Denso" company...? I used their ND-U plugs for
years in my motorcycle and they ran great! I see the commercial for
the Iridium plugs with teh U groove side electrode. Tempting, indeed!



John Robertson said:
I have had many cars with aluminium head and never had success with bosch
plugs .I use anti seize because of my experience with bosch .I prefer NGK
plugs because of this very reason .As this is over many cars and millions of
miles it pays .Motor craft were good till they stopped making them in Japan
.
Click to expand...

__ __
Randy & \ \/ /alerie's
\__/olvos
'90 245 Estate - '93 965 Estate
"Shelby" & "Kate"
 
Randy G. said:
ALWAYS use anti-seize when plugs go into an alloy head.

Your plug problem may have been caused by either the Bosch plugs beign
just a little longer than othre brands in th threads, or they might
have run just a bit cooler (or both) causing excessive carbon build up
making them difficult to get out....?

I see commercials for "Denso" spark plugs. I am assuming that this is
the renamed "Nippon Denso" company...? I used their ND-U plugs for
years in my motorcycle and they ran great! I see the commercial for
the Iridium plugs with teh U groove side electrode. Tempting, indeed!
Click to expand...


There's probably cases where this is wrong, but I've never had anything
great to say about any of the fancy gimmicky spark plugs. I tried Bosch
Platinum plugs a couple times, in one car the electrodes wore down
surprisingly fast and another ran like absolute crap under boost and took
forever to track down, now I always use plain old NGK plugs and have never
had any problems at all with them.
 
James Sweet said:
There's probably cases where this is wrong, but I've never had anything
great to say about any of the fancy gimmicky spark plugs. I tried Bosch
Platinum plugs a couple times, in one car the electrodes wore down
surprisingly fast and another ran like absolute crap under boost and took
forever to track down, now I always use plain old NGK plugs and have never
had any problems at all with them.
Click to expand...

That may be the case. I know that the ND U groove made a big
difference in the way the bike ran, and like you, I had very bad
results in the same vehicle with the Bosch platinum. This was in a
vehicle with points and standard kettering ignition (12 v system,
single set of points, with two 6 v. coils).

I think the New Denso has an exposed center electrode as opposed the
the "hidden" electrode on the Bosch plugs.



__ __
Randy & \ \/ /alerie's
\__/olvos
'90 245 Estate - '93 965 Estate
"Shelby" & "Kate"
 
James Sweet said:
There's probably cases where this is wrong, but I've never had anything
great to say about any of the fancy gimmicky spark plugs. I tried Bosch
Platinum plugs a couple times, in one car the electrodes wore down
surprisingly fast and another ran like absolute crap under boost and took
forever to track down, now I always use plain old NGK plugs and have never
had any problems at all with them.
Click to expand...
That was my experience using Bosch platinums in the 765T. Within a year
there were only holes where the center electrodes were and the engine was
misfiring under load. Some say other brands don't do that but I'm happy with
regular NGKs.

Mike
 
I lied ,the other day I saw Bosch plugs 4 four AU $37.50 at super cheap
here in Melbourne .They had 4 earths and a small centre pointed in such a
way that they should maintain their gap for a long time ,100.000 KLMS I was
told .I used such plugs on an Alfa I once had they made a huge difference
..so I will see .By the way number one plug was a fair cow to get in right so
they havent changed their ways ,they still jamup in the treads .
 
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