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[garethbuck]

I have a niggling problem which seems to be pretty common but as yet I have not seen a common fix. The mileage is 83k

1) when hot, if i switch her off for a couple of mins then on again the oil pressure does not come up as it should.

2) From cold or warm the needle reads over 3 ie to the right of vertical on the guage and as it heats up it reads either vertical or slightly under when I am cruising at 60mph. ie about 1700rpm.

3) The handbook says to use 5w30 oil, the main dealer who serviced it when it was new used 10w40 and wilco say to use 15w40....hmm

4) it had 15w40 in it so I replaced it with a 5w30 and used a mopar filter after flushing the engine to see what it did and the situation became slightly worse.

5) I have tried a WIX filter and it improved. Interestingly when I had both the wix and the mopar filters both removed and full of oil. If i inverted them the wix one drained slowly and the mopar one didnt. The both look identical but obviously the spring in the mopar one is providing more resistance.

6) I have noticed that many similar posts report ussued after an oil filter change, so I am wondereing if this engine sensitive to back pressure from the filter???

7)I have not verified the pressure with a manual guage and know this is something I should do. My gut feel tells me its right though.

There is no smoke or untoward noises.

SO the options would seem to be

- the pressure sensor, but why would this only be affected with hot thin oil?  Unless its reading generally low and is out of calibration in some way. But surely it would not read as it does with a cold/ warm engine?

- the oil pressure release valve sticking open

- the oil pump is worn

- The engine is worn, but where is the smoke? knocks and rattles?

- something else weird like a cracked oil pipe

I was hoping to find some pointers here but apart from seeing a lot of posts from people with this issue I have not really read anything about what  caused the issue from people who have resolved it.

I wait with baited breath.....All help appreciated

[Tragic]

:shock:
GET THAT 5W30 OUT OF THERE!!!!

I recall reading somewhere that is a misprint in the manual

A 6-cylinder 4.0 should be either 10w40 or 15w40 semi synthetic.
5w30 is for Ford Zetecs, you may as well be running wd40 in your Jeep!

Sticky pressure switches seem to be a quite common problem (mine also does it). Use a Mopar filter and it should be fine.

[garethbuck]

My local main dealer also told me 5W30 is the correct oil. I know this old lump would probably run on lard or chip fat but it does not exactly make me confident when everone says something different, then adds if you use the wrong one you will destroy the engine.

Anyway, I drained the oil yesterday and am now using a cheap multigrade 15w30 from Wilco to see what happens... It has made a difference but is still low when hot. I cruised 20 niles at 60mph this morning. all seemed ok until I stopped and waited for a couple of mins. When I started her up again, then bing "check guages" bing.

It was doing more mpg on 5w30 though, but it was only in there for a few days.

the article i found  by Larry Carley

http://www.aa1car.com/library/us1097.htm

is interesting though.

[tim_aka_tim]

Listen to Tragic - 10W40 or 15W40 semi-synthetic is what you need in the 4 litre.

[Mike Pavelin]

Get a mechanical oil pressure gauge and check it properly.

With the correct oil and a Mopar filter (anything else is a waste of money and probably more expensive to buy) the factory figures hot are 13 psi at 600rpm and min 37psi-75psi max above 1600 rpm.

[PtP]

My gauge was all over the place when I first bought my Wrangler a couple of years ago and I recall it’s a common problem. I replaced the sender unit with one from Lighthouse and the gauge has been fine ever since. I'm not sure this is the root of your problem though!

[demonicwillow]

Alot of filters now come with check valves built in, so they hold thier oil when removed from the engine, as written before the only true way of checking the oil pressure is with a oil pressure test guage non electrical and when the engine is at its operating temp, as long as its within its spec and the correct oil is in there dont worry about extreme guage movements, mine on the xj is up the two thirds when cold, revs or idleing, then as it warms up its on a third at idle then shoots to 1/2 to two thirds under revs.  

[Bishops Finger]

Owners manual suggests 10/30w


Been advised 10/40W....

[garethbuck]

Soo.....

I really need an oil that is 10 weight when cold so it gets to the right places quickly, and the pressure is fine when its cold/warm...but when hot and I mean "hot" the thinner oil gets too thin and the pressure drops too much.

Although my temperature stats at a constant vertical 100 mark, I do notice the oil pressure dropping after I have driven 20 miles or so.

I guess the fully synthetics or high quality race oils are designed for this and are more likely to keep better viscosity under high temperatures, either that or I could try a 10w50 oil that would not be so thin as a 10w40 when hot.

Does this sound reasonable?

[PtP]

I’m running my 4.0l TJ on Carlube 5w40 Fully Synthetic (about £15 +VAT for 5 litres from Makro) and the oil pressure on the standard gauge is very stable hot or cold. I’ve been using this for the last couple of years now and have done around 10k miles in that time – I think I’ve only done around 55k in total now.

Also, for what it’s worth, the emissions on the recent MOT test were very low at:

Fast Idle Test
CO - Limit – Max 0.20%   Mine 0.00%
HC – Limit – Max 200ppm   Mine 5 ppm
Lambda – Limit – 0.97-1.03   Mine 1.00

Natural Idle Test
CO – Limit – Max 0.30%   Mine 0.00%

[garethbuck]

my jeep is gas converted, a friend said it is possible that this makes it run hotter? It seems to run very well on LPG and I dont have any desire to run on petrol.

[JamesH]

Fully synthetic can be a little risky in a flat tappet engine.

Some of these oils are developed for newer technology engines that don't have the friction points of older style, flat tappet engines. If the fully synthetic oil doesn't have high enough levels of ZDDP (zinc based friction reducer) it could lead to increase camshaft and associated component wear.

API SL grade oil is the last standard considered suitable for flat tappet engines and API SM or newer definitely shouldn't be used. Having the aPI SL designation doesn't ensure correct levels of ZDDP but could be considered a minimum standard to check for when considering oil.

[PtP]

Thanks for that James.

I’ve just checked the container in the garage and it quotes that it’s “….manufactured to the latest API SL/CF specifications,….”  It also quotes the following codes which I’ve no idea what they are: ACEA A3, B3, B4.

All this talk of oil, reminds me that I probably should change it soon! Do I stick with what I’ve got or use something different?

[JamesH]

I'm no expert, the previous post probably exhausted my knowledge on the subject.

I always put 10w40 semi-synthetic in mine so can't really offer a view on alternatives. I think with standard camshaft and internals the 4.0l should be pretty tolerant.

The reports of serious wear and failures have been in more modified engines with higher valve spring pressures and potentially less-well-made camshafts and lifters.

[Jonny Jeep]

Just to confuse the issue more (or clarify it)...

:shock:  
GET THAT 5W30 OUT OF THERE!!!!

This is from the factory service manual...

ENGINE OIL

SAE VISCOSITY RATING INDICATES ENGINE OIL VISCOSITY

An SAE viscosity grade is used to specify the viscosity
of engine oil. SAE 30 specifies a single viscosity
engine oil. Engine oils also have multiple
viscosities. These are specified with a dual SAE viscosity
grade which indicates the cold-to-hot temperature
viscosity range.
SAE 30 = single grade engine oil.
SAE 10W-30 = multiple grade engine oil.

API QUALITY CLASSIFICATION

The API Service Grade specifies the type of performance
the engine oil is intended to provide. The API
Service Grade specifications also apply to energy conserving
engine oils.
Use engine oils that are API Service Certified.
5W-30 and 10W-30 MOPAR engine oils conform to
specifications.

And from the API (American Petroleum Institute) website...

If an automotive owner's manual calls for an API SJ or SL oil, an API SM oil will provide full protection.

http://http://www.api.org/certifications/engineoil/categories/upload/EngineOilGuide2006.pdf

So 5W-30 is fine (it is actually the recommended oil grade in the 2005 FSM) and API-SM rated oils are good "For all automotive engines currently in use." - quoted from the PDF linked to above.

Also from FSM...

ACEA Categories

For countries that use the ACEA European Oil
Categories for Service Fill Oils, use engine oils that
meet the requirements of ACEA A1/B1, A2/B2, or
A3/B3.

[Bubba]

well i think we have beaten this bush to death

[demonicwillow]

Just to confuse the issue more (or clarify it)...

:shock:  :roll:


 

[JamesH]

Just some more info on ZDDP levels and flat tappet engines.

From HotRod magazine http://http://www.hotrod.com/techarticles/engine/flat_tappet_cam_tech/index.html:

Faced with ever more stringent emissions standards and the governmental mandate for extended emissions-control- system warranties, the OEMs gottogether with the motor oil makers and decided to reduce the amount ofZDDP in street-legal, gasoline-engine motor oils. After all, theyweren't needed with modern roller lifters and overhead-cam followers.The reduction first started in the mid-'80s, and it has been a gradual process, but the latest API SM and GF-4 specs have reduced ZDDP content to such an extent that the new oils may not provide adequate protectionfor older, flat-tappet-equipped vehicles running nonstock, performance cams and valvetrains. And it will only get worse; projected future oilspec revisions will likely reduce ZDDP content even more.


Like I said before though, in a standard engine the increase in wear from incorrect oil probably isn't going to cause a drastic failure.

[Dave69]

the bottom line is everyone has their view on what oil to put in an engine, being the 4ltr it's of an old design so the oil galleries are slightly larger than a modern engine, irrespective what the ink on the paper says 10/30 or 40 multigrade semi synthetic oil will be used. a 5 weight oil is designed for a more modern engine with tighter tollerances.

as long as the engine oil is changed reasonably often then it's doesn't matter all that much what you put in.

the oil pressure guages either work or they dont, i keep thinking of swapping mine to a more modern form with approprite wiring.

[bonza]

the bottom line is everyone has their view on what oil to put in an engine,

this is absolutely correct

I've been involved with this for years and the mechanical engineers I work with and who are my peers, rarely agree on brand of oil, except to change it regularly and keep the engine internals clean.

but we are on agreeance with the following

5W-30 or 10W-30 is too light. it is an attempt to improve fuel economy, but in the long term leads to cam shaft wear.
dont use SM specified oils, seek the older classified SL oils.(less zinc)

10W-40 such as Mobil super XHP approved to API sl,sj,cf is preferable for the 4 liter engine. other brands such as Valvoline are just as good.

10W-30 has a vicosity of 10.5 cSt @ 100 deg C.
10W-40 viscosity 14.5 cSt @ 100 deg C.

and just because oil is marketed in a flash looking container with a fancy name doesn't make it better than oil sourced from a red 44 gallon drum. check the tech details when buying it

only use 10W-30 if you only drive short distances in freezing conditions

but what would I know.