[x300] Cracked exhaust manifold experiences

I would like to find out more about results after welding or
replacing the cracked exhaust manifolds. I’m interested mostly in
MPG increase, smoother idle.
I’m about to sell my car because of these problems.–
95’XJ6 VDP 4.0L, Flamenco Red, San Pedro California
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In reply to a message from Tibor Makai sent Sat 19 May 2007:

They are designed to crack. Updated headers out here are both
illegal and IIRC not available. I crack all of mine and it will
take me 2-3 years at 1mpg additional to pay the cost back for both
where they will likely crack again during that time. I just drive
with them the way they are.

The XJ6 will do 15.5-17.5 city, 22-25 highway depending on speed,
distance, traffic. I’m ok with that for cracked headers. The idle
quality is very smooth with no lope or stumble. It actually made
me wonder if the coils are different because if they aren’t I would
swap all 6 into the XJR to see if the sporadic stumble goes away
before MAF cleaning, O2’s etc. The idle quality of the XJ6 is very
good compared to just good on the XJR.

What are your symptoms and other parts examined to affect your idle
quality? You can’t tell except by listening closely the XJ6 has
cracked headers. Are you positive it isn’t something else?

http://www.jag-lovers.org/snaps/snap_view.php3?id=id=1083550709&n4=

Sunny–
The original message included these comments:

I would like to find out more about results after welding or
replacing the cracked exhaust manifolds. I’m interested mostly in
MPG increase, smoother idle.


Sunny Garofalo, '97 XJ6, '95 XJR
Northridge, CA, United States
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In reply to a message from Tibor Makai sent Sat 19 May 2007:

My 96 VDP had a visible crack in the rear exhaust manifold. When it
was removed for repair I also found one that you could not see. I
also removed front manifold and had it checked and refaced. I took
mine to a shop that works on aluminum heads. They did the refacing,
magniflux[looking for cracks] and repaired the cracks by
brazing.Total price was $45.00. When I reinstalled I used the old
gasket. About 6000 MLS so far and all is well. Idle always has been
smooth , before and after, no idea on MPG, Nick–
The original message included these comments:

I would like to find out more about results after welding or
replacing the cracked exhaust manifolds. I’m interested mostly in
MPG increase, smoother idle.


Nick ,67E-Type 67S-Type 65S-Type96VDP
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In reply to a message from Tibor Makai sent Sat 19 May 2007:

Tibor, I’m sticking my neck out here but rough idle would be
more to do with clogged injectors IMO. My 4.0 does mid 20’s
mpg (UK gallons - mainly fast roads, part urban), better
than my old 2.3 inline 4 did. Even if I boot it (not often)
it still does 23-25.

I’ve never felt the idle is as smooth as I’d like, hoped all
the new parts in the fuel system would help but no
difference as yet. No cracks that I know of in my manifolds,
if there are they aren’t killing my MPG and there’s no sooty
marks behind the heatshields. If they did crack I’d probably
bite the bullet and get a S/S set from AJ6 engineering, but
I don’t believe they do any for the US lambda sensor setup.

Good luck whatever you decide to do.–
The original message included these comments:

I would like to find out more about results after welding or
replacing the cracked exhaust manifolds. I’m interested mostly in
MPG increase, smoother idle.
I’m about to sell my car because of these problems.


Regards, Bruce. 1995 XJ Sport 4.0
Colchester, Essex, United Kingdom
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In reply to a message from -TiberiuS- sent Sun 20 May 2007:

I’m not sure from where is coming the lumpy idle. I just changed my
spark plugs with the hotter once RC12YC, which made a slight
difference but not much. I’m cleaning my TB every six months with
no noticeable difference. I had oil around the spark plugs(three
places), but after cleaning them and re tightening the top seal,
stopped leaking. I even put Teflon tape around the coils(over
cracks), filed the deposits around the coils, checked for vacuum
which is in specs, changed the fuel filter. The only two things
left is the cracks on the manifolds and cleaning the injectors.
I’m driving each day to work 14 miles each way from which maybe 1.5
miles are street miles and I end up with 17.2 MPG at the next fill
up. The gas tank won’t fill up all the way(it fills up to the line
between the 3/4 and full), this could cause some problems with the
idle or MPG?
Another diagnosis I did is with the a scanner(Proscan, which is not
working with the latest 5.0 software, only with the older one 4.0A
with a lot of error codes and very bad customer support, do not buy
from them), what I come up is that my downstream O2 sensors show
the same diagram then the upstream once, which is not good in my
opinion. Or my catalytic converter is bad or the crack introduces
to much Oxygen, I’m I correct?
Any help is appreciated here, since I wouldn’t like to sell my car,
but if nobody can help me out here I will have to sell my car and
buy something like a new VW Rabbit or Suzuki SX4 which they can be
compared with my Jaguar.–
95’XJ6 VDP 4.0L, Flamenco Red, San Pedro California
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In reply to a message from Tibor Makai sent Sun 20 May 2007:

When the main cat begins to go it will go quickly and give you a
catalyst efficiency code regularly. By itself, a bad main catalyst
won’t cripple you below the 20mpg mark doing 65-75mph most of your
trip. I drove with a bad one for several weeks doing a 11mi
commute each way with half being a 45mph surface street and 4 stop
lights. Have you checked to see how lean your fuel trims are
trying to go to correct the rich mixture and cleaning your MAFS?
Can you confirm your car is going into closed loop and you’re
running at normal temperature? 180ish?

Sunny–
Sunny Garofalo, '97 XJ6, '95 XJR
Northridge, CA, United States
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In reply to a message from Tibor Makai sent Sat 19 May 2007:

If you like the car in other respects Tibor, why not buy a set of
the fabricated AJ6 stainless manifolds and forget cracking ever
again? Not cheap but they work with the rest of the standard system
and if you do indeed like the car in other respects they’d be
cheaper than replacing the vehicle…–
Peter Crespin 66E, 76 DD6 Coupe, 84 DD6, 85 XJS 5sp convert
Cambridge, United Kingdom
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In reply to a message from Tibor Makai sent Sun 20 May 2007:

Tibor, I did pretty much the same as you - new TPS, FPR,
filters, several bouts of TB stripping and cleaning,
rochester/dump valves, looms checked, lots of cleaning and
regreasing connectors, new relays, regapped sparkplugs,
copious amounts of injector cleaner…none of the above has
had any influence at all on my original power loss problem
or rough idle and the power loss issue is gradually getting
worse.

With the rough idle, it’s never been as smooth as I’d hoped.
It’s not misfire rough - the tacho is always steady - but
it’s unstable enough to buffet the car at times, enough for
passengers to notice.

The fuel tank not registering full is a common fault with
the original senders, reading 3/4 when the tank is really
full - either that or the common tank venting problem - I
doubt either of which would cause rough idle or bad MPG.

But, it’s the nature of the beast and I wouldn’t be happy
selling it for another make of car…I’d be back, I know I
would.

Good luck.–
The original message included these comments:

I’m not sure from where is coming the lumpy idle. I just changed my
spark plugs with the hotter once RC12YC, which made a slight
difference but not much. I’m cleaning my TB every six months with
no noticeable difference. I had oil around the spark plugs(three
places), but after cleaning them and re tightening the top seal,
stopped leaking. I even put Teflon tape around the coils(over
cracks), filed the deposits around the coils, checked for vacuum
which is in specs, changed the fuel filter. The only two things
left is the cracks on the manifolds and cleaning the injectors.


Regards, Bruce. 1995 XJ Sport 4.0
Colchester, Essex, United Kingdom
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In reply to a message from -TiberiuS- sent Mon 21 May 2007:

Thank you for everybody who answered, greatly appreciated.
Peter, I believe that those headers they won’t work without some
modifications on a Californian car(air injection) and it’s a bit
expensive to spend that much when the whole car is worth ~$6000.
The car enters in close loop. Here are some numbers:
Short term fuel trim: 3.1-7.8% rich
Long term fuel trim: 52.3% rich
Short term fuel trim 2: 0-4.7% rich
Long term fuel trim 2: 52.3%
Engine RPM: 672-699
Ignition timing: 8 deg.(sometimes is 11)
Air intake: 127.4 F
MAF air flow: 0.04 g/s 0 lb/min
Throttle: 0% (but sometimes is 12.5%) at idle
Oxy sensor B1-S1: 0.04-1.235 V
Oxy sensor B1-S2: 0.04-1.235 V
Oxy sensor B2-S1: 0.06-1.245 V
Oxy sensor B2-S2: 0.04-1.225 V
Coolant temp: 168 deg.
Engine load(%): 2 (sometimes 14.1)
All the data at idle with Proscan 4.0A(5.0 not connecting with my
car).
Somebody who welded his manifolds and are still OK could give me
the procedure how to do it correctly?
About the my gas tank, I believe my problem is with some clogged
pipe in the purging system or something similar because when I fill
it up I can squeeze in only about 13-14 gallons. Sometimes I can
fill it up all the way(not the last couple of fill ups).–
95’XJ6 VDP 4.0L, Flamenco Red, San Pedro California
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In reply to a message from PeterCrespin sent Mon 21 May 2007:

I agree with Peter the stainless steel manifolds would be a
great solution.
The s/s exhaust manifolds are from TDC,Torque Developments
or AJ6 Engineering IIRC ?
When I last investigated, none were compatible with the USA
O2 sensor requirements.Does anyone know if this has changed?
Has anyone adapted the U.K. manifold for USA use? I think it
requires welding of 2 extra threaded bosses for the extra O2
sensors on the USA models?–
The original message included these comments:

If you like the car in other respects Tibor, why not buy a set of
the fabricated AJ6 stainless manifolds and forget cracking ever
again? Not cheap but they work with the rest of the standard system
and if you do indeed like the car in other respects they’d be
cheaper than replacing the vehicle…


95 XJR, 69 E-Type ots,89 RX-7 conv,97 Miata
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In reply to a message from anthony davenport sent Tue 22 May 2007:

I looked at both, and you would need to weld on two bosses for the
air pump lines, and one on the rear for the the EGR pipe. I think
it would be very strait forward.

In the case of the AJ6 product, you retain the OE down pipes so the
O2 sensors are not an issue.

On the TDL, you would need to add bosses for the second set.

Both products are pricy.–
The original message included these comments:

The s/s exhaust manifolds are from TDC,Torque Developments
or AJ6 Engineering IIRC ?
When I last investigated, none were compatible with the USA
O2 sensor requirements.Does anyone know if this has changed?
Has anyone adapted the U.K. manifold for USA use? I think it
requires welding of 2 extra threaded bosses for the extra O2
sensors on the USA models?


uncle
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