Hi,

after years reading your very helpful posts I decided to register
to share some questions I have about my 1991 XJ with I6 4.0L
with Renix fuel system . 5 speed AX15 and NP231 transmision.

I bought it in dec. 2002 with only 90000 miles, now after 6.5 years
using without great problems I reached 112K miles (yes only 21K ran
this is a small country and gas is very expensive :-) )

From the begining I noted a slight oil wet in the block-head line just
above the serial number plate, the wet extended about 3 or 4 inches
but somthing quite solid, not liquid oil and kept in its place for years.
This year I noticed and increment and expansion of oil leak with a more
liquid aspect running to the rear through the block-head line due to
engine backwards inclination and moistening the block at the side of the block, near distributor. Oil seems clean, coolant at the bottle seems clean
too.

I use almost from the begining Liqui-Moly 10W40 MoS2 (with anti friction
molibdeno compound), is quite luiquid due to its low grade in cool.
Due to a valvle lifter "tac" sound I had, in my previous oil change I used
Liqui-Moly hydrostobel to clean the valve steams and after 2 days the sound dissapeared and never came again. I am running with a new oil change so the hydrostobel product should not be present anymore in the engine.

2 days ago put some red hi-temp head gasket silicone to the line from
where the oil is comming out, previously a deep clean using contacts cleaners that left the block very clean and dry. This is only a temporally
measure. My question is to inquire which could be the cause, since the engine runs very powerful and smooth even more with new Bosh 4 holes injectors (one Bendix-Deka was leaking but this is other story for other moment) and new original Mopar ignition wire set.

Might this a loosen bolt in the head ? the driver side's bolts are outside
the valvle cover but the passanger side's bolts are under the valvle cover,
could I remove the VC and tighthen the bolts, to do this is required to remove the rocker arm ? I will look for pictures at home before putting the
silicone to show the problem and will post here if possible.

Any suggestion about the cause of this slight (increasing) leak will be much appreciated, I live in Uruguay and taking the Jeep to a shop is worst that put a burning match in the gas tank, they will break several other parts in the procedure (due to lack of knowledge of the car), put any part in the market that will shurely not be suitable for this car (no parts at all here for Jeeps) and will charge you even more than the value of the car. Until know I managed to make all maintenance by myself, I'd like to keep this way.


Thank you for any help and best regards from the very south!

Charly

PS : excuses for my english writing mistakes


Jeep XJ 1991 4.0L - AX15 5 speed manual - NP231 - BFG 30x9.50x15

Other Jeeps in the family putting our hand on them for years :
****** Overland Station Wagon 1963 with Bedford 220 Diesel
Jeep Commando 1972 C104 with Nissan LD28 6I Diesel

 

Hi Charly,

 

Hi Mike,

thank you for your kind reply, I had really forgotten about that issue, in fact, I just kept the hi-temp silicone all along the cylinder head joint line with the block and stopped any oil leak until now, perhaps with the time a new sediment may form in the joint and seal the leak again, according to what I read, the hydrostobel like products make have this side effect, anyway the leak was not so big and is by now blocked by the silicone.

After I replaced the leaking Bendix-Deka injectors by the Bosh 4 holes rebuilt, the ones used by Ford Mustang V8 and that were compatible with my original ones, I started experiencing a new problem, after the engine warms, the idle speed go too fast, about 1200 to 1500 rpm instead of the ~600 of a normal idle speed. I checked everything, all the sensors are operating within their range (temp sensors), I replaced the MAP sensor without any change, the only way I accidentally found to reduce the hi idle RPMs was causing a controlled vacuum leak to the MAP sensor, I installed a medical line with a flow restrict manual valve and when the engine is warm and idle RPMs have went up, I open the valve and cause some vacum leak between the throttle body vacuum port and the MAP sensor, this immediately reduces the idle RPM (but it should be exactly in the opposite fashion according to my previous experience with a leaking line to the MAP sensor!!).
For any reason the equations in the system have reversed, but at least I can keep the low idle RPMs until I find the solution (a year and more going...). Mileage have reduced about 40% !

I have found a lot of carbon debris in the exhaust pipe, is very probably the leaking injector was working badly for a long time causing out of time injections and bad detonations, this might have cause the formation of carbon rests.

The EGR might have been affected by these carbon deposits, the EGR transducer that I have checked recently had the back pressure port filled with carbon debris, I cleaned it as much as possible and verified the air is flowing normally, then reinstalled but nothing changed.

Now I must remove the EGR and make a deep clean, mainly in the back pressure pipe (a small diameter one), I suspect a lot of carbon is inside restricting EGR back pressure flow, the EGR diaphragm is working properly
reducing the idle RPM when I move the pintle by hand.

As a last option, I suspect the flow rate of these bosh injectors sold to me as an exact replacement for the original Bendix-Deka, might have a much more flow rate, although according to specifications it is only a 5% more and the engine works fine, smother and powerful.

I hope to be able to check the EGR in these days and finally return to my normal mileage that considering the 4.0L displacement, the weight of the vehicle, it is not so bad after all compared to 1.6L engines and lighter cars, I obtained (before this problem) in city an average of 150kms/20Lts and in highway I even reached 205Kms/20Lts using A/C and at about 120Km/h.

Any help or information of any of the members here will be much appreciated.

Best regards and happy 2011 for everyone!


Carlos

 

As for the oil leak they seem to be very common... mine does on the pass side... I think it has something to do with milage and the length of the motor... with the inline six being a long skinney motor I would imagin over time the head would warp slightly from the block... just as the exhaust manifolds do and later crack... I really don't think you will run into any problems with the leak... sometimes after higher miles it better to use a thicker oil... this will help slow down any kind of leaks... oil pan leaks... rear main seals... front cam seals... all that generally start to seep at this age... I just let mine go... I don't have a fancy driveway to worry about drips here and there... its probly better not to clean as the wet oil collects dust and can actually slow the leak... (kind of like flushing a tranny at 200k when its never been done... hurts more then it helps)... as for the injector swap I do believe it is recommended to use a different fuel regulator with the 19# injectors... I remeber I got mine from a specific dosage caravan... can't remember the part number though... maybe that will help your problem?

 

Mine has the leak there as well, thought it was from VC, but nope. Drive it till the gasket goes completely then replace.

 

mine had same leak ook it in didnt feel like messing with taking off the head, the did the head gasket.... still leaked took it back they shaved the head and put another new gasket on still leaked.... it is now in for the third time