91 overheating

Hello there -

My '91 4 door automatic has been annoying me for a couple of years now.

Three years ago, the transmission was replaced, exhaust also. Since then, i
have had an overheating problem while accelerating. Any thing over 2500
will make the temperature jump.

I have replaced the guage sender, the radiator, hoses, water pump and fun
clutch over the past few years as these were more or less worn out.

To make things livable, i have drilled a couple of extra holes in the
thermostat. It takes a while to warm up, but the temp sits at the "o" in
normal. Hit the gas and watch it jump for a minute or two and go back to
where it started. Yes, the engine really does get hot. Without the holes,
i was overheating when it was 15 below zero. Tried replacing the oxygen
sensor - no change.

It doesn't matter if driving or reving in neutral - same thing - temp spike
when accelerating.

Sounds like it is running lean?

190,000 miles.

Could it be an issue with our newer blends of gas?

Help,

Randy

On Wed, 31 Aug 2005 23:12:42 -0500, "Randy Johnson" >
wrote:

>Hello there -
>
>My '91 4 door automatic has been annoying me for a couple of years now.
>
>Three years ago, the transmission was replaced, exhaust also. Since then, i
>have had an overheating problem while accelerating. Any thing over 2500
>will make the temperature jump.
>
>I have replaced the guage sender, the radiator, hoses, water pump and fun
>clutch over the past few years as these were more or less worn out.
>
>To make things livable, i have drilled a couple of extra holes in the
>thermostat. It takes a while to warm up, but the temp sits at the "o" in
>normal. Hit the gas and watch it jump for a minute or two and go back to
>where it started. Yes, the engine really does get hot. Without the holes,
>i was overheating when it was 15 below zero. Tried replacing the oxygen
>sensor - no change.
>
>It doesn't matter if driving or reving in neutral - same thing - temp spike
>when accelerating.
>
>Sounds like it is running lean?
>
>190,000 miles.
>
>Could it be an issue with our newer blends of gas?
>
>Help,
>
>Randy
>

Any chance you have the thermostat in backwards?

"Randy Johnson" > wrote in message
...
> Hello there -
>
> My '91 4 door automatic has been annoying me for a couple of years now.
>
> Three years ago, the transmission was replaced, exhaust also. Since then,
i
> have had an overheating problem while accelerating. Any thing over 2500
> will make the temperature jump.
>
> I have replaced the guage sender, the radiator, hoses, water pump and fun
> clutch over the past few years as these were more or less worn out.
>
> To make things livable, i have drilled a couple of extra holes in the
> thermostat. It takes a while to warm up, but the temp sits at the "o" in
> normal. Hit the gas and watch it jump for a minute or two and go back to
> where it started. Yes, the engine really does get hot. Without the
holes,
> i was overheating when it was 15 below zero. Tried replacing the oxygen
> sensor - no change.
>
> It doesn't matter if driving or reving in neutral - same thing - temp
spike
> when accelerating.
>
> Sounds like it is running lean?
>
> 190,000 miles.
>
> Could it be an issue with our newer blends of gas?
>
> Help,
>
> Randy
>
>
Did it begin when when the exhaust was replaced? I have not had this
particular problem yet but while researching MY overheating problems I read
that a blocked catalytic converter could cause overheating.

I'm about to replace my radiator and fan clutch in a few minutes. I'm
pretty sure my fan clutch is bad (it turns freely when the engine is hot and
I never get that "whoosh" sound any more) and my radiator is clogged. If
that doesn't work I'll be doing all the other things that you did (not sure
about drilling holes in my thermostat though) so please post any progress
you make and solutions you may find. I thought I'd solved the problem on my
'92 but the temp gauge went up while I was going up a steep hill. The rest
of the time the temp gauge barely moves. I put in a new thermostat not very
long ago. I guess I'll have to yank it out and test it. At least it's not
dumping coolant any more when I shut off the engine. My '91 is close to
being undrivable right now unless the outside temp is 90 F or less.

Ashton Crusher wrote:
>
> Any chance you have the thermostat in backwards?

That theory seems like it fits the facts. The thermostat would still
work, but delayed since heat would have to conduct thru the body of the
thermostat to reach the expansion capsule part of the thermostat. The
capsule is supposed to be immersed in the hot water of the engine
block. So the spring side goes toward the radiator, the capsule is on
the hot side and expands and pushes the valve open against the spring.

By drilling holes in the thermostat, hot water from the jacket is able
to jet against the capsule, causing it to expand and opening the valve.
That explains why the holes help, and why the engine even overheats in
very cold weather- it's going to be a lot harder to get that capsule
hot enough to open if it's on the cold side, and the cold side is below
freezing.

I think Ashton's right.
-Paul

Ashton Crusher wrote:
>
> Any chance you have the thermostat in backwards?

That theory seems like it fits the facts. The thermostat would still
work, but delayed since heat would have to conduct thru the body of the
thermostat to reach the expansion capsule part of the thermostat. The
capsule is supposed to be immersed in the hot water of the engine
block. So the spring side goes toward the radiator, the capsule is on
the hot side and expands and pushes the valve open against the spring.

By drilling holes in the thermostat, hot water from the jacket is able
to jet against the capsule, causing it to expand and opening the valve.
That explains why the holes help, and why the engine even overheats in
very cold weather- it's going to be a lot harder to get that capsule
hot enough to open if it's on the cold side, and the cold side is below
freezing.

I think Ashton's right.
-Paul

"Ulysses" > wrote in message
...
>
> "Randy Johnson" > wrote in message
> ...
> > Hello there -
> >
> > My '91 4 door automatic has been annoying me for a couple of years now.
> >
> > Three years ago, the transmission was replaced, exhaust also. Since
then,
> i
> > have had an overheating problem while accelerating. Any thing over 2500
> > will make the temperature jump.
> >
> > I have replaced the guage sender, the radiator, hoses, water pump and
fun
> > clutch over the past few years as these were more or less worn out.
> >
> > To make things livable, i have drilled a couple of extra holes in the
> > thermostat. It takes a while to warm up, but the temp sits at the "o"
in
> > normal. Hit the gas and watch it jump for a minute or two and go back
to
> > where it started. Yes, the engine really does get hot. Without the
> holes,
> > i was overheating when it was 15 below zero. Tried replacing the oxygen
> > sensor - no change.
> >
> > It doesn't matter if driving or reving in neutral - same thing - temp
> spike
> > when accelerating.
> >
> > Sounds like it is running lean?
> >
> > 190,000 miles.
> >
> > Could it be an issue with our newer blends of gas?
> >
> > Help,
> >
> > Randy
> >
> >
> Did it begin when when the exhaust was replaced? I have not had this
> particular problem yet but while researching MY overheating problems I
read
> that a blocked catalytic converter could cause overheating.
>
> I'm about to replace my radiator and fan clutch in a few minutes. I'm
> pretty sure my fan clutch is bad (it turns freely when the engine is hot
and
> I never get that "whoosh" sound any more) and my radiator is clogged. If
> that doesn't work I'll be doing all the other things that you did (not
sure
> about drilling holes in my thermostat though) so please post any progress
> you make and solutions you may find. I thought I'd solved the problem on
my
> '92 but the temp gauge went up while I was going up a steep hill. The
rest
> of the time the temp gauge barely moves. I put in a new thermostat not
very
> long ago. I guess I'll have to yank it out and test it. At least it's
not
> dumping coolant any more when I shut off the engine. My '91 is close to
> being undrivable right now unless the outside temp is 90 F or less.
>
>
Well, my fan clutch was all oil and goopy on the thermostat and there was so
much mud on the radiator that it was probably only working about 15-20%.
Considering that I now have 3 Exploders I decided to just go ahead and put
in the new radiator and keep the old one for a spare.

I went up some steep dirt hills in 4WD with the AC on and now the temp goes
up about halfway (100 F here today) and then drops back down to about one
forth of the way up. It will now idle at a stop with the AC on without
overheating. That's a big improvement but I have not given it the windy
mountain road test yet.

Thanks for the try -

The thermostat is in the correct way. I have tried a couple of
thermostats over the past couple of year. It took a while to figure out
that three holes were necessary to make it work - two holes were not enough.

Randy


> wrote in message
oups.com...
>
> Ashton Crusher wrote:
>>
>> Any chance you have the thermostat in backwards?
>
> That theory seems like it fits the facts. The thermostat would still
> work, but delayed since heat would have to conduct thru the body of the
> thermostat to reach the expansion capsule part of the thermostat. The
> capsule is supposed to be immersed in the hot water of the engine
> block. So the spring side goes toward the radiator, the capsule is on
> the hot side and expands and pushes the valve open against the spring.
>
> By drilling holes in the thermostat, hot water from the jacket is able
> to jet against the capsule, causing it to expand and opening the valve.
> That explains why the holes help, and why the engine even overheats in
> very cold weather- it's going to be a lot harder to get that capsule
> hot enough to open if it's on the cold side, and the cold side is below
> freezing.
>
> I think Ashton's right.
> -Paul
>

Not sure about right after the exhaust work. When it was done, the
temperature gauge stopped working. That was replaced and all seemed well at
that time.

We don't use the truck very much the past couple of years - about 4,000
miles a year.

The temperature problem became evident when we pulled out pop-up camper on a
trip that ended up abruptly in West Virginia when the pump blew out on the
transmission. Stupid me had the transmission rebuilt instead of junking the
truck. Since then any time you go over 2,200 or so RPM - the temperature
climbs about 30 seconds after you hit the gas.

The radiator hoses are also new and don't appear like they could collapse.
I havent found any that have the coil spring inside like some others.

Any other ideas?

Randy
"Ulysses" > wrote in message
...
>
> "Ulysses" > wrote in message
> ...
>>
>> "Randy Johnson" > wrote in message
>> ...
>> > Hello there -
>> >
>> > My '91 4 door automatic has been annoying me for a couple of years now.
>> >
>> > Three years ago, the transmission was replaced, exhaust also. Since
> then,
>> i
>> > have had an overheating problem while accelerating. Any thing over
>> > 2500
>> > will make the temperature jump.
>> >
>> > I have replaced the guage sender, the radiator, hoses, water pump and
> fun
>> > clutch over the past few years as these were more or less worn out.
>> >
>> > To make things livable, i have drilled a couple of extra holes in the
>> > thermostat. It takes a while to warm up, but the temp sits at the "o"
> in
>> > normal. Hit the gas and watch it jump for a minute or two and go back
> to
>> > where it started. Yes, the engine really does get hot. Without the
>> holes,
>> > i was overheating when it was 15 below zero. Tried replacing the
>> > oxygen
>> > sensor - no change.
>> >
>> > It doesn't matter if driving or reving in neutral - same thing - temp
>> spike
>> > when accelerating.
>> >
>> > Sounds like it is running lean?
>> >
>> > 190,000 miles.
>> >
>> > Could it be an issue with our newer blends of gas?
>> >
>> > Help,
>> >
>> > Randy
>> >
>> >
>> Did it begin when when the exhaust was replaced? I have not had this
>> particular problem yet but while researching MY overheating problems I
> read
>> that a blocked catalytic converter could cause overheating.
>>
>> I'm about to replace my radiator and fan clutch in a few minutes. I'm
>> pretty sure my fan clutch is bad (it turns freely when the engine is hot
> and
>> I never get that "whoosh" sound any more) and my radiator is clogged. If
>> that doesn't work I'll be doing all the other things that you did (not
> sure
>> about drilling holes in my thermostat though) so please post any progress
>> you make and solutions you may find. I thought I'd solved the problem on
> my
>> '92 but the temp gauge went up while I was going up a steep hill. The
> rest
>> of the time the temp gauge barely moves. I put in a new thermostat not
> very
>> long ago. I guess I'll have to yank it out and test it. At least it's
> not
>> dumping coolant any more when I shut off the engine. My '91 is close to
>> being undrivable right now unless the outside temp is 90 F or less.
>>
>>
> Well, my fan clutch was all oil and goopy on the thermostat and there was
> so
> much mud on the radiator that it was probably only working about 15-20%.
> Considering that I now have 3 Exploders I decided to just go ahead and put
> in the new radiator and keep the old one for a spare.
>
> I went up some steep dirt hills in 4WD with the AC on and now the temp
> goes
> up about halfway (100 F here today) and then drops back down to about one
> forth of the way up. It will now idle at a stop with the AC on without
> overheating. That's a big improvement but I have not given it the windy
> mountain road test yet.
>
>
>

On Fri, 2 Sep 2005 22:33:36 -0500, "Randy Johnson" >
wrote:

>Not sure about right after the exhaust work. When it was done, the
>temperature gauge stopped working. That was replaced and all seemed well at
>that time.
>
>We don't use the truck very much the past couple of years - about 4,000
>miles a year.
>
>The temperature problem became evident when we pulled out pop-up camper on a
>trip that ended up abruptly in West Virginia when the pump blew out on the
>transmission. Stupid me had the transmission rebuilt instead of junking the
>truck. Since then any time you go over 2,200 or so RPM - the temperature
>climbs about 30 seconds after you hit the gas.
>
>The radiator hoses are also new and don't appear like they could collapse.
>I havent found any that have the coil spring inside like some others.
>
>Any other ideas?
I had a pickup that would sound like it was overheating when I shut it
off, you could hear the coolant start to boil. I replaced the
radiator cap and that fixed it. Since caps are cheap and you've tried
most stuff I give a new cap a try. You should also consider the fan
clutch, the difference between good and bad doesn't feel like much to
the "hand" but can make a big difference. On my old mustang a new
clutch cooled it down about 20 degrees and changed it from nearly
overheating on a hot day to running like it should. You may have
already done this stuff, I don't recall the start of the thread.

Randy Johnson wrote:
> Thanks for the try -
>
> The thermostat is in the correct way. I have tried a couple of
> thermostats over the past couple of year. It took a while to figure out
> that three holes were necessary to make it work - two holes were not enough.
>

Those holes can't let thru nearly as much hot water as an open
thermostat. Is there an obstruction or something that's keeping it from
opening? Is it sticking and then popping open? Try putting the
thermostat in a pan on the stove and see how it opens. Stick a meat
thermometer in with it to measure the temperature at which it's
opening. They usually start opening at 180 degrees F. It should be
wide open as the water nears boiling. You can also try installing a 160
degree thermostat. That might solve your problem by brute force.

I just can't believe that three little holes work if the thermostat is
installed properly and working properly.

You say "Hit the gas and watch it jump for a minute or two and go back
to
where it started." That seems to eliminate the rest of the cooling
system- it wouldn't heat up and then "go back to where it started"
after a lag if it was the radiator or waterpump. It sure sounds like
there is a lag in your thermostat opening.

-Paul