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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / May 2008

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'96 Rodeo 4 cyl - A/C cuts out related to water temp

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p5388@wildblue.net - 30 Apr 2008 02:37 GMT
My wife's everyday ride is a '96 Isuzu Rodeo, it has been giving me
fits for the past couple of years starting around this time of year.
On hotter days, the A/C will cut off when the temp gage reaches the
3/4 mark. The engine temp never goes beyond this 3/4 mark, but this is
more noticeable on trips of a couple of hours or more. Especially
where cruising speed is around 70mph for a long period of time.
I would assume there is a cut out for the reason of dropping engine
operating temp as the condenser creates extra heat when the A/C is on.
I keep the maintenance up on this - oil change every 3K, timing belt
and valve adjust every 50K - It has 225K miles on it.  The radiator
has been flushed, water pump replaced twice, thermostat replaced -
what else would raise operating temperature on "hot" days?
Thanks in advance..
Mike - 30 Apr 2008 03:38 GMT
> My wife's everyday ride is a '96 Isuzu Rodeo, it has been giving me
> fits for the past couple of years starting around this time of year.
[quoted text clipped - 9 lines]
> what else would raise operating temperature on "hot" days?
> Thanks in advance..

 A partially plugged or restricted radiator. If it is the original radiator I
would think about replacing it if everything else checks out.
Scott Dorsey - 30 Apr 2008 13:58 GMT
>> My wife's everyday ride is a '96 Isuzu Rodeo, it has been giving me
>> fits for the past couple of years starting around this time of year.
[quoted text clipped - 12 lines]
>  A partially plugged or restricted radiator. If it is the original radiator I
>would think about replacing it if everything else checks out.

By flushed, do you mean it has had an acid flush or just a water flush?

I sort of recommend the acid flush... if the radiator or block is partially
plugged, the acid flush will often open things up.  The bad news is that if
something is held together by corrosion, the acid flush will cause it to come
apart and you will find all kinds of things leaking that you never had leaking
before.  But, I figure they are all things that probably need to be replaced
anyway.

I agree that almost certainly you have a clogged radiator.  The acid flush
may open it up, and it may also make it leak like mad.  If the latter happens,
well, you needed to replace it anyway.

Oh yes, also make sure your engine timing is right on.  Almost certainly
this isn't the problem, but check it anyway.
--scott
Signature

"C'est un Nagra.  C'est suisse, et tres, tres precis."

p5388@wildblue.net - 01 May 2008 02:17 GMT
> In article <0ZQRj.2348$Cn4....@news02.roc.ny>, Mike <m...@localnet.com> wrote:
>
[quoted text clipped - 19 lines]
> --
> "C'est un Nagra.  C'est suisse, et tres, tres precis."

The radiator has been flushed with an acid flush, also I have not been
able to detect any cold spots in the radiator.  The last water pump I
put on, I did a test flow while the radiator was off, and volume
output seemed more than adequate. I also washed out the fins of the
radiator, but they really weren't that dirty.

I have thought about the fan clutch, although it seems to be "stiff"
when cold and "free" when heated up

I will check the ignition timing to make sure, but I check it "by the
book" each time I put a new timing belt on.

Thanks for all the input - sooner or later we'll get this resolved, at
28 mpg, I sure hate to give up on it.
Scott Dorsey - 01 May 2008 15:11 GMT
>The radiator has been flushed with an acid flush, also I have not been
>able to detect any cold spots in the radiator.  The last water pump I
>put on, I did a test flow while the radiator was off, and volume
>output seemed more than adequate. I also washed out the fins of the
>radiator, but they really weren't that dirty.

I'm still thinking gunked-up radiator.  If the radiator is partially clogged
already the acid flush won't do it much good.  

>I have thought about the fan clutch, although it seems to be "stiff"
>when cold and "free" when heated up

This is bad.  It should be the other way around... the thing is supposed to
become stiff when it gets hot in order to make the fan go faster when the
engine is hot.  

However, if the problem is happening at 70 mph, it probably isn't related
to the fan.  At highway speeds, plenty of air is going through the radiator
so that you don't need the fan at all.  In heavy traffic, the fan is critical.

>I will check the ignition timing to make sure, but I check it "by the
>book" each time I put a new timing belt on.
>
>Thanks for all the input - sooner or later we'll get this resolved, at
>28 mpg, I sure hate to give up on it.

Try this: take the thermostat out completely.  If you do this, the engine
should be running WAY abnormally cold.  Does it?
--scott
Signature

"C'est un Nagra.  C'est suisse, et tres, tres precis."

Steve B. - 01 May 2008 22:11 GMT
>>The radiator has been flushed with an acid flush, also I have not been
>>able to detect any cold spots in the radiator.  The last water pump I
[quoted text clipped - 4 lines]
>I'm still thinking gunked-up radiator.  If the radiator is partially clogged
>already the acid flush won't do it much good.  

I agree, especially at that mileage.  Even if the tubes are clear the
fins can get corroded and loose their ability to efficiently remove
heat.

>>I have thought about the fan clutch, although it seems to be "stiff"
>>when cold and "free" when heated up
>
>This is bad.  It should be the other way around... the thing is supposed to
>become stiff when it gets hot in order to make the fan go faster when the
>engine is hot.  

It should be stiff if the engine was very hot but it won't be very
stiff at normal operating temperature.  It will also be stiff when it
is cold...  that's why you hear the fan "roar" for a couple of seconds
on cold start.
mr.som ting wong - 04 May 2008 16:43 GMT
is it possible the ac is overcharged???

> > In article <0ZQRj.2348$Cn4....@news02.roc.ny>, Mike <m...@localnet.com> wrote:
> >
[quoted text clipped - 34 lines]
> Thanks for all the input - sooner or later we'll get this resolved, at
> 28 mpg, I sure hate to give up on it.
Steve B. - 30 Apr 2008 03:48 GMT
>My wife's everyday ride is a '96 Isuzu Rodeo, it has been giving me
>fits for the past couple of years starting around this time of year.
[quoted text clipped - 9 lines]
>what else would raise operating temperature on "hot" days?
>Thanks in advance..

First thing to do is find out if it is really getting that hot or if
you just have a temp sending unit that has  gone out of spec.  If it's
cheap enough I usually just replace the sending unit and see if there
is a change.

Next thought would be a clogged radiator.  Any decent radiator shop
should have a heat gun and be able to check the radiator for cold
spots (indicates clogged radiator with no water flowing through that
area).  At 225k it's a pretty safe bet that you have some radiator
issues.

          Steve B.
aarcuda69062 - 30 Apr 2008 13:01 GMT
In article
<902be3f8-8396-4bdc-9539-e2cf36e3a701@25g2000hsx.googlegroups.com>,

> My wife's everyday ride is a '96 Isuzu Rodeo, it has been giving me
> fits for the past couple of years starting around this time of year.
[quoted text clipped - 9 lines]
> what else would raise operating temperature on "hot" days?
> Thanks in advance..

Check for debris in the radiator and condenser fins.
Check the fan clutch.
 
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