Help 3.9L oil capacity issue

Nza wrote:

> ...The check engine light comes on after about 30 miles on the highway..
> every time...

That may very well be the oil pressure switch in need of replacement
rather than actual low oil pressure. Less than $20 for the part. That
is one part you should get from the dealer - aftermarket pressure
switches are often so far out of cal right out of the box as to give
false low oil pressure indication. OEM parts generally at least start
out having been tested to higher standards (tighter tolerances).

Anyway - very common for these switches to fail on Chrysler vehicles -
and when they do, it seeems it's always in the direction of falsely
indicating low pressure - and often leaking oil too.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

On Aug 8, 6:55 pm, Bill Putney > wrote:
> Nza wrote:
> > ...The check engine light comes on after about 30 miles on the highway..
> > every time...
>
> That may very well be the oil pressure switch in need of replacement
> rather than actual low oil pressure. Less than $20 for the part. That
> is one part you should get from the dealer - aftermarket pressure
> switches are often so far out of cal right out of the box as to give
> false low oil pressure indication. OEM parts generally at least start
> out having been tested to higher standards (tighter tolerances).
>
> Anyway - very common for these switches to fail on Chrysler vehicles -
> and when they do, it seeems it's always in the direction of falsely
> indicating low pressure - and often leaking oil too.

Thanks Bill, will get one of those soon.

That doesn't explain the rise in temperature, though.. turning on the
heater to max heat brings the temp back down a bit and keeps it at bay
(on a long highway drive). I haven't tried it on a long drive since
it's been 90+ outside, though.

Nza wrote:

> The check engine light comes on after about 30 miles on the highway..
> every time. The coolant temp starts to climb about that time as
> well. I am thinking water pump. Can the water pump set the check
> engine light?

Only indirectly by causing an over-temp that might set the light.

Overheating after prolonged operation usually comes down to lack of
coolant flow or lack of air flow. Since this happens on the highway, its
*probably* not an air flow issue, but some cars don't flow enough air
through the radiator without a good fan even at highway speeds. Just to
be sure, check the fan clutch and check the radiator and condensor fins
for dead bugs, grass, dirt, leaves, etc. For water flow, make sure the
radiator isn't clogged (if the oil was neglected, I'll bet the coolant
was also!). Make sure the thermostat opens and opens all the way, and
make sure the lower hose doesn't collapse. Also make sure the radiator
cap pressurizes the system fully.

On Aug 9, 12:48 pm, Steve > wrote:
> Nza wrote:
> > The check engine light comes on after about 30 miles on the highway..
> > every time. The coolant temp starts to climb about that time as
> > well. I am thinking water pump. Can the water pump set the check
> > engine light?
>
> Only indirectly by causing an over-temp that might set the light.
>
> Overheating after prolonged operation usually comes down to lack of
> coolant flow or lack of air flow. Since this happens on the highway, its
> *probably* not an air flow issue, but some cars don't flow enough air
> through the radiator without a good fan even at highway speeds. Just to
> be sure, check the fan clutch and check the radiator and condensor fins
> for dead bugs, grass, dirt, leaves, etc. For water flow, make sure the
> radiator isn't clogged (if the oil was neglected, I'll bet the coolant
> was also!). Make sure the thermostat opens and opens all the way, and
> make sure the lower hose doesn't collapse. Also make sure the radiator
> cap pressurizes the system fully.

ok i'll check all those... now that you remind me, the radiator is
pretty scaly inside. The coolant was brown when I first got it
because it was just water..

I will definitely check the fan clutch as well. It's amazing how
quickly all this troubleshooting ability seems to disappear now that i
don't do it every day for a paycheck...

Nza wrote:


> ok i'll check all those... now that you remind me, the radiator is
> pretty scaly inside. The coolant was brown when I first got it
> because it was just water..
>

I think you just identified the problem... :-p

The question now is whether just a rigorous flushing will clear it up
enough, or whether you'll have to have the radiator rodded out.