Followup-- 2000 JGC V-8 still overheating

I posted this several weeks ago, and got a lot of thoughtful replies. No
remedy yet, this is just an update.

Last week, I drove home from vacation, a 500 mile trip. I noticed
repeatedly that the temp at 65 mph would be in the 205-210 range, but five
minutes after I go up to 75 mph, the temp would increase to around 225. I
did this test over and over, and got the same results.

Someone suggested that to check the (new) thermostat, to take the pressure
cap off when the engine is cold, start the engine, and see if there is water
flow (I assume there should be flow after the thermostat opens up). I did
this test, while the outside temp is 72 degrees. From the first engine
start, I saw no water flow. None.

I let the engine run for 45 minutes. The gauge went to 205 and stayed
there. At no time did I see a water flow, even after 45 minutes of running
at idle. I put my finger in the water and it was **warm** but not at all
hot. Just warm. It never got hot.

Should I have seen water flow after the temp went to 205, and the engine
ran for 45 mins ??


Any further comments will be appreciated.



--James--




----------------------------------------------------------------------------
-------------------------------

This is a V-8, 120 K miles. It usually runs around 200-210
> degrees. During last six months or so, it will go up the 235 degrees when
> traveling over 70 mph. It will also do this when going up a medium
> incline, even at very slow speed.
>
> It stays 100% normal at slow speeds, and at idle, such as at a traffic
> light.
>
> Fan clutch was replaced fairly recently, that DID relate to heating some
> at idle.
>
> I am thinking either I need radiator work or a new radiator OR that I
> may have a bad thermostat. I suppose I could also have a defective
> water pump at high speeds, but that wouldn't explain why it overheats on
> medium inclines even at slow speeds.
>
> BTW, some folks may say 235 degrees is normal under some circumstances. I
> can assure you that this is NOT normal, as I have driven this car for six
> years and I know how it performs.
>
> What is most likely culprit? Themostat/Water Pump/Radiator
>
> If it is radiator, is it worth it to have it re-rodded, or is it best just
> to install a new radiator?
>
> As a non-mechanic, are these any tests I can do to narrow it down more?
> (Water pump does not leak).
>
>
> Thanks for any tips !!!
>
> --James--

Did you touch the radiator at different spots/corners to see if it was
getting hot at all? Upper radiator hose getting hot?

Might be a partially clogged radiator and the area where you touched with
your finger is part of the clogged area where the coolant possibly stays
cooler.
I would assume that if the water pump was not functioning then that engine
should overheat just idling.

Just a theory.
later,
dave AKA vwdoc1

"James" > wrote in message
. ..
>I posted this several weeks ago, and got a lot of thoughtful replies. No
> remedy yet, this is just an update.
>
> Last week, I drove home from vacation, a 500 mile trip. I noticed
> repeatedly that the temp at 65 mph would be in the 205-210 range, but
> five
> minutes after I go up to 75 mph, the temp would increase to around 225.
> I
> did this test over and over, and got the same results.
>
> Someone suggested that to check the (new) thermostat, to take the
> pressure
> cap off when the engine is cold, start the engine, and see if there is
> water
> flow (I assume there should be flow after the thermostat opens up). I
> did
> this test, while the outside temp is 72 degrees. From the first engine
> start, I saw no water flow. None.
>
> I let the engine run for 45 minutes. The gauge went to 205 and stayed
> there. At no time did I see a water flow, even after 45 minutes of
> running
> at idle. I put my finger in the water and it was **warm** but not at
> all
> hot. Just warm. It never got hot.
>
> Should I have seen water flow after the temp went to 205, and the engine
> ran for 45 mins ??
>
>
> Any further comments will be appreciated.
>
>
>
> --James--
>
>
>
>
> ----------------------------------------------------------------------------
> -------------------------------
>
> This is a V-8, 120 K miles. It usually runs around 200-210
>> degrees. During last six months or so, it will go up the 235 degrees
>> when
>> traveling over 70 mph. It will also do this when going up a medium
>> incline, even at very slow speed.
>>
>> It stays 100% normal at slow speeds, and at idle, such as at a traffic
>> light.
>>
>> Fan clutch was replaced fairly recently, that DID relate to heating some
>> at idle.
>>
>> I am thinking either I need radiator work or a new radiator OR that I
>> may have a bad thermostat. I suppose I could also have a defective
>> water pump at high speeds, but that wouldn't explain why it overheats on
>> medium inclines even at slow speeds.
>>
>> BTW, some folks may say 235 degrees is normal under some circumstances.
>> I
>> can assure you that this is NOT normal, as I have driven this car for six
>> years and I know how it performs.
>>
>> What is most likely culprit? Themostat/Water Pump/Radiator
>>
>> If it is radiator, is it worth it to have it re-rodded, or is it best
>> just
>> to install a new radiator?
>>
>> As a non-mechanic, are these any tests I can do to narrow it down more?
>> (Water pump does not leak).
>>
>>
>> Thanks for any tips !!!
>>
>> --James--
>
>

The place where I was touching was in the water itself. I took the pressure
cap off for the test. The water is just under the cap.

--James--

I would be thinking that the thermostat that is supposed to open at 195
has serious issues.

You should have burned your finger in 205 coolant. Water boils just
slightly hotter than that....

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)

James wrote:
>
> I posted this several weeks ago, and got a lot of thoughtful replies. No
> remedy yet, this is just an update.
>
> Last week, I drove home from vacation, a 500 mile trip. I noticed
> repeatedly that the temp at 65 mph would be in the 205-210 range, but five
> minutes after I go up to 75 mph, the temp would increase to around 225. I
> did this test over and over, and got the same results.
>
> Someone suggested that to check the (new) thermostat, to take the pressure
> cap off when the engine is cold, start the engine, and see if there is water
> flow (I assume there should be flow after the thermostat opens up). I did
> this test, while the outside temp is 72 degrees. From the first engine
> start, I saw no water flow. None.
>
> I let the engine run for 45 minutes. The gauge went to 205 and stayed
> there. At no time did I see a water flow, even after 45 minutes of running
> at idle. I put my finger in the water and it was **warm** but not at all
> hot. Just warm. It never got hot.
>
> Should I have seen water flow after the temp went to 205, and the engine
> ran for 45 mins ??
>
> Any further comments will be appreciated.
>
> --James--
>
> ----------------------------------------------------------------------------
> -------------------------------
>
> This is a V-8, 120 K miles. It usually runs around 200-210
> > degrees. During last six months or so, it will go up the 235 degrees when
> > traveling over 70 mph. It will also do this when going up a medium
> > incline, even at very slow speed.
> >
> > It stays 100% normal at slow speeds, and at idle, such as at a traffic
> > light.
> >
> > Fan clutch was replaced fairly recently, that DID relate to heating some
> > at idle.
> >
> > I am thinking either I need radiator work or a new radiator OR that I
> > may have a bad thermostat. I suppose I could also have a defective
> > water pump at high speeds, but that wouldn't explain why it overheats on
> > medium inclines even at slow speeds.
> >
> > BTW, some folks may say 235 degrees is normal under some circumstances. I
> > can assure you that this is NOT normal, as I have driven this car for six
> > years and I know how it performs.
> >
> > What is most likely culprit? Themostat/Water Pump/Radiator
> >
> > If it is radiator, is it worth it to have it re-rodded, or is it best just
> > to install a new radiator?
> >
> > As a non-mechanic, are these any tests I can do to narrow it down more?
> > (Water pump does not leak).
> >
> >
> > Thanks for any tips !!!
> >
> > --James--

Yes, Mike, I agree with your comments. My mechanic put in a new
thermostat just several months ago. I wonder if it was installed backwards.
Could that be ?


--James--

Or just plain a bad one.... That happens. I think yours must be
opening 'some' or you would get a boil over.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)

James wrote:
>
> Yes, Mike, I agree with your comments. My mechanic put in a new
> thermostat just several months ago. I wonder if it was installed backwards.
> Could that be ?
>
> --James--

On Sat, 13 Jan 2007 13:22:24 -0500, Mike Romain >
wrote:

>Or just plain a bad one.... That happens. I think yours must be
>opening 'some' or you would get a boil over.


I fully disagree here. He can keep chasing monkeys but I am pretty
sure it is one of three problems. THe first that the core is blocked
externally with dirt and bugs limiting air flow through it. The second
is the clutch fan is bad because contray to popular belief ram air
will not always cool engine especaily when a big V8 is packed in a
small compartment. Some seem to think that they never good bad but the
thermostatic coil on them ages and when it does it retards the
operation of the fan. (I have posted instruction on how to adjust the
clutch fan in my forum) When it is 220 or so the fan should be a
humping. The thrid is the core is blocked internally which can happen
if proper coolant quality is not maintained. I would check it in that
order or you can just keep chasing the monkey around and never catch
it.
-----------------
TheSnoMan.com

SnoMan, I had the fan clutch replaced about four months ago. Yes, I know
it could be defective, but talk about chasing monkeys, I am not quite ready
to put another clutch in. You posted a very good article on adjusting the
fan, but my mechanic indicates that for the labor involved, he would only go
with another new fan. I am not ready for it, as I see that as doubtful.

When you say the "core" could be blocked, exactly what part do you mean ?
Are you speaking of the radioator itself ? I am thinking more and more
that it is the radiator. Perhaps you mean the radiator core, huh?

Can a flow test be done without removing the radiator?


--James--

On Sat, 13 Jan 2007 14:26:05 -0500, "James" >
wrote:

>SnoMan, I had the fan clutch replaced about four months ago. Yes, I know
>it could be defective, but talk about chasing monkeys, I am not quite ready
>to put another clutch in. You posted a very good article on adjusting the
>fan, but my mechanic indicates that for the labor involved, he would only go
>with another new fan. I am not ready for it, as I see that as doubtful.
>
>When you say the "core" could be blocked, exactly what part do you mean ?
>Are you speaking of the radioator itself ? I am thinking more and more
>that it is the radiator. Perhaps you mean the radiator core, huh?
>
>Can a flow test be done without removing the radiator?
>
>
>--James--
>


First when the engine overheats is the clutch fan engaging? Next on
the blocked core it could be that the external part where air flows
through is blocked with dirt or bugs or the fins are badly smashed
blocking airflow. Internally, you might find a shop to flow test it in
car but not too likely. Feel core of raditor (if possible) and see if
it is evenly heating up. I still stand by my 3 suggestions. because
the symptoms match it.
-----------------
TheSnoMan.com

If something was indeed blocked, he would get boiling fluid pouring out
the open radiator cap in the test. He has cool non moving fluid only
with the inside gauge reading above the temp an open thermostat would be
working at.

He could have no real problems with the rad and a wonky sender for the
gauge.

Mike

SnoMan wrote:
>
> On Sat, 13 Jan 2007 13:22:24 -0500, Mike Romain >
> wrote:
>
> >Or just plain a bad one.... That happens. I think yours must be
> >opening 'some' or you would get a boil over.
>
> I fully disagree here. He can keep chasing monkeys but I am pretty
> sure it is one of three problems. THe first that the core is blocked
> externally with dirt and bugs limiting air flow through it. The second
> is the clutch fan is bad because contray to popular belief ram air
> will not always cool engine especaily when a big V8 is packed in a
> small compartment. Some seem to think that they never good bad but the
> thermostatic coil on them ages and when it does it retards the
> operation of the fan. (I have posted instruction on how to adjust the
> clutch fan in my forum) When it is 220 or so the fan should be a
> humping. The thrid is the core is blocked internally which can happen
> if proper coolant quality is not maintained. I would check it in that
> order or you can just keep chasing the monkey around and never catch
> it.
> -----------------
> TheSnoMan.com