Nathan Plemons

Cool, I'm sure that was mentioned, I just skimmed over the posts too quickly to see it.

R Cook 92

it is becoming pretty long... thanks for the input though, I apprieciate any help I can get.

PeteL

Lets make sure we have this correct:

1.) If you jump A&B on a ALDL connector the fan(s) runs.

2.) With the engine running and the temperature up to 240*, the fan does not run.

3.) With the engine running and up to 235* AND and AC turned to ON full cold, the fan does not run - even after a couple of minutes?

Questions:

Are all the above correct?

Does your AC produce cold air, does it work?

R Cook 92

All is correct.

The A/C does work, but when the temp is 240 it doesn't blow cold air, it is hot air, but it blows hard. It did blow cold after I got moving...
Randy

pfast89

Mine had the same symtoms and it turned out to be the a/c high pressure switch. The ECM never knew the a/c was on!

Ray Zavorka

Randy:

Much of what Pete L stated is right on target, but I would like to add a point or two. Noting that you are from Illinois and assuming that you are going to drive there this winter, I would use care in selecting your new thermostat in an attempt to circumvent frost bitten fingers and, toes and most importantly, to minimize the potential for sludge build up in the cold weather months ahead...

Please do not spin off in a million directions at once - you will just be spending money! R&R the thermostat (with stock stat), do a cooling system maintenance using the proper coolant (not some "Poly Raz A Mataz" gunk) and take it from there.
Please also note in your original post that you stated that you went from 280 degrees to normal just by driving the car! I have said it before and I will say it again - Air Flow (or a lack of it) is the biggest Corvette cooling problem - Check those fans carefully and clean out the debris fron the radiator area...

Ray

Ray Zavorka

Happened to stumble on this at anothe forum after my previous post NOTE - Long):

1.Re: 1996 GMC Jimmy - SLUDGE PROBLEM
: I’ve read all the comments out there on this problem with the sludge in the radiator. My question
to everyone with this problem in the past is “Did flushing the cooling system and putting green
coolant back in it cure the problem and have you have any other problems related to this?” Has it
overheated, freeze plugs rusting out, or any other problems?: My cousin resently bought a 96
GMC Jimmy w/62,000 miles. With the previous owner (someone I work with) at 54,181 miles (out
of warranty) - the dealer replaced at no charge the radiator, water pump, thermostat and
serpentine belt and put the dexcool back in it. Now, at 67,000 miles it has reoccurred, but the
intake manifold gasket was cracked/leaking. She has had it flushed and green coolant put back in
it. I have done some research and GM does have a sevice bulletin on this problem
(#99-06-02-012B - which I have) and it goes into detail on flushing the system step-by-step (9
pages) . Any help with my questions would be greatly appreciated.: : Thanks, Cindy:I switched to
the green coolant after replacing the radiator, heater core,and water pump. I have not had any
problems so far.

2.Re: 1997 Blazer, coolant problem
: Four months after my 97 Blazer was out of warranty the engine started running hot. I took it to
an\: independent servicer and was informed the coolant that last for 5 years or 100,000 miles was
sludge: and had eaten the intake manifold gasket. The rest of the coolant was sitting in the oil
pan. This repair: cost over $400. Several days latter the engine developed a knock. I took it back
the the independent who: was honest enough to admit he was no sure where the knock
originated. His advice was to drive the: vehicle another week and see if the knock got worse. In
the meantime i decided to take the vehicle : to a Chevy dealer, i was then informed by them it
needed a new engine at a cost of $5000. I immediately: called GM customer service, after all was
said and done the diagnosis was that somewhere along the : line the vehicle blew an oil cooler
line, not. And oil was lost from the engine when this happened, not.: And they were not going to
pay for anything. Never was it found that maybe their sludged coolant: got into the engine
scouring the main bearings.They decided that it was a lack of oil and there was: no other cause.
Never has an oil cooler hose been replaced. I really want to fight GM they should take:
responisiblity for a weak product. If anyone out there has had a similiar experience please E-mail
me. Thanks:Look at the post on this board 96 Jimmy coolant problems and my post on the
archive board, 96 Blazer - Sludge From Dexcool dated 11/09/00. You will see comments from
many others who have had the same problem. Someone suggested a class action suit, but I don't
know how to get one started.

3.Re: 98 blazer dex cool turns to sludge / gurgling noise near dash
So you're saying that because GM says you can be ignorant about flushing a cooling system and
you still got 90K miles out of it you're upset with GM? Let me guess, you haven't changed the
plugs either singe they're also good for 100K miles. From what I've heard, even though the coolant
SAYS it's good for 100K miles, it should still be flushed on a regular basis, mainly for the reason
you just described, it turns to sludge. Have you ever topped the coolant up? Did you use Dexcool
or the regular green coolant? They SHOULD NOT be mixed! To fix your problem, the heater core
needs to be flushed. Have you had any other problems with the truck to warrant you calling it a
"piece of junk"?: What a piece of junk my 98 blazer 90k dex cool has turned too sludge , replaced
the radiator now I have a gurgling noise behind the dash while driving. Now I am waiting for the
sludge to form AGAIN. I will NEVER BUY A CHEVY AGAIN>

4.Re: Mike L. / Dex Coolant Sludge
: I should have been more specific about my situation. I believe in preventive maintainence for all
my chevy vehicles that I have owned. I follow the required vehicle maintainence exactley and do
some extra. I had to replace my first radiator at about 40 k just after my warrenty expired there
was sludge and a few leaks. I always top off my coolant WITH DEX COOL. Why does it say it is
good for 100k when in all reality I probably only got 35 k out of it. I just recently flushed it again
when I replaced a broken water pump....then one month later I needed another flush again. As for
the truck being a piece of junk, I have yet to mention the spider gears in the front end that had to
be replaced at about 40 k. Did I mention the weeks my car was at a Chevy dealership while they
tried to figure out what was wrong with the front end. When you say the coolant should be flushed
on a regular basis do you mean ONCE A MONTH? So I guess you can see why CHEVY IS A
PIECE OF JUNK.:If you go back through this message board to October of 2000, you will see
many complaints about Dexcool. It has even been suggested that a class action suit should be
filed. Sludge occurred in Blazers and Jimmys of various years. It is obvious to me that a chemical
reaction between Dexcool and metal or gaskets results in sludge formation. After replacing the
radiator, water pump, heater core, and having a 6hr flush, I had the dealer put in the old reliable
green ethylene glycol. I have not had a problem since the fix, but plan on flushing my system
every 2 years.

5.96 Blazer A/C problems
sloshing water sound (Dexcool got me) matt 09:54:21 6/13/01

6.sloshing water sound (Dexcool got me)
sloshing water sound (Dexcool got me)

7.1996 GMC Jimmy - SLUDGE PROBLEM
I’ve read all the comments out there on this problem with the sludge in the radiator. My question
to everyone with this problem in the past is “Did flushing the cooling system and putting green
coolant back in it cure the problem and have you have any other problems related to this?” Has it
overheated, freeze plugs rusting out, or any other problems?My cousin resently bought a 96 GMC
Jimmy w/62,000 miles. With the previous owner (someone I work with) at 54,181 miles (out of
warranty) - the dealer replaced at no charge the radiator, water pump, thermostat and serpentine
belt and put the dexcool back in it. Now, at 67,000 miles it has reoccurred, but the intake
manifold gasket was cracked/leaking. She has had it flushed and green coolant put back in it. I
have done some research and GM does have a sevice bulletin on this problem (#99-06-02-012B -
which I have) and it goes into detail on flushing the system step-by-step (9 pages) . Any help with
my questions would be greatly appreciated. Thanks, Cindy

8.Re: DEX-COOL lawsuit
: Has anyone pursued a class action suit againt GM for the use and known problems wit
DEX-COOL? I am now getting the run around from the Dealer and the warranty people about this
even though this problem is quite common. This problem is costing us all a lot of money. Any
ideas?:My message from May.If you go back through this message board to October of 2000,
you will see many complaints about Dexcool. It has even been suggested that a class action
suit should be filed. Sludge occurred in Blazers and Jimmys of various years. It is obvious to me
that a chemical reaction between Dexcool and metal or gaskets results in sludge formation. After
replacing the radiator, water pump, heater core, and having a 6hr flush, I had the dealer put in the
old reliable green ethylene glycol. I have not had a problem since the fix, but plan on flushing my
system every 2 years.I also, now think that the water slushing sound from the heater core is tied
to this problem.Same question - if anyone knows how to initiate a class action suit I'm in!

9.Re: 1996 GMC Jimmy - SLUDGE PROBLEM
: I’ve read all the comments out there on this problem with the sludge in the radiator. My question
to everyone with this problem in the past is “Did flushing the cooling system and putting green
coolant back in it cure the problem and have you have any other problems related to this?” Has it
overheated, freeze plugs rusting out, or any other problems?: My cousin resently bought a 96
GMC Jimmy w/62,000 miles. With the previous owner (someone I work with) at 54,181 miles (out
of warranty) - the dealer replaced at no charge the radiator, water pump, thermostat and
serpentine belt and put the dexcool back in it. Now, at 67,000 miles it has reoccurred, but the
intake manifold gasket was cracked/leaking. She has had it flushed and green coolant put back in
it. I have done some research and GM does have a sevice bulletin on this problem
(#99-06-02-012B - which I have) and it goes into detail on flushing the system step-by-step (9
pages) . Any help with my questions would be greatly appreciated.: : Thanks, CindyA Friend of
mine has a 96 blazer---had the sludge problem about 2 months ago...took it to the dealer. He said
that used a GM flushing agent (tried to buy some from them but they wouldnt sell, said it was
listed as a Hazardous Material) and flushed the system 3-4 times. They told him that the problem
is that green coolant does not mix well with dexcool remains that are in the system and create
the tar like sludge---I think he is running green now. Just glad I have a 95 that came with the green
stuff in it originally.

10.Re: 1996 blazer
: 1996 blazer LS. I hear liquid moving: from the inside of my car. When I accelerate it sounds like
either the a/c freon or the engine coolant is moving. Does anybody else have this problem. What
you describe is a common symptom of Dexcool problems. Start with the following threads to
learn about how nasty it is.
http://forums.chevytalk.com/forums/F...sages/768.html

11.Re: 1996 GMC Jimmy - SLUDGE PROBLEM
: : I’ve read all the comments out there on this problem with the sludge in the radiator. My
question to everyone with this problem in the past is “Did flushing the cooling system and putting
green coolant back in it cure the problem and have you have any other problems related to this?”
Has it overheated, freeze plugs rusting out, or any other problems?: : My cousin resently bought a
96 GMC Jimmy w/62,000 miles. With the previous owner (someone I work with) at 54,181 miles
(out of warranty) - the dealer replaced at no charge the radiator, water pump, thermostat and
serpentine belt and put the dexcool back in it. Now, at 67,000 miles it has reoccurred, but the
intake manifold gasket was cracked/leaking. She has had it flushed and green coolant put back in
it. I have done some research and GM does have a sevice bulletin on this problem
(#99-06-02-012B - which I have) and it goes into detail on flushing the system step-by-step (9
pages) . Any help with my questions would be greatly appreciated.: : : : Thanks, Cindy: A Friend
of mine has a 96 blazer---had the sludge problem about 2 months ago...took it to the dealer. He
said that used a GM flushing agent (tried to buy some from them but they wouldnt sell, said it
was listed as a Hazardous Material) and flushed the system 3-4 times. They told him that the
problem is that green coolant does not mix well with dexcool remains that are in the system and
create the tar like sludge---I think he is running green now. Just glad I have a 95 that came with
the green stuff in it originally.This is what I know about this problem. About two years ago my
dealer advised me on the QT to get the original "permanent" coolant out of my '96 Blazer, or else
my system would be gummed up forever.

12.Re: 1998 Blazer-Problems, Problems, Problems
: I've got a 3 year old Blazer that has had several problems arise in the past few weeks. I had to
have the radiator completely replaced. $600 repair by dealer: My a/c system just went down as
well. The air compressor has to be replaced. $1100 repair by dealer: Has anyone had problems
with their radiator or a/c systems. It is out of warranty, but the truck is only 3 years old. Maybe its
just my time for some bad luck.: I have a 96 and had rear end problems 6000 miles out of
warranty. I called Chevy and got them to pay for most of the repair, so you may want to give them
a try. Regarding the radiator, if it was a Dexcool problem you may want to checkout the other
posts.

13.Dexcool victims
Dexcool victims

Ray

PeteL

Need some LT1 help here guys. The fans are not turning on. Doesn't somebody here have an LT1 manual to help this guy out?

This is down to checking ECM inputs I think. Could be the ECM temp sensor, could be the ECM, but could be other things. This problem now requires particular wires to probe for specific voltages and so forth.

Does anybody with an LT1 know where the temp sensor for the ECM is? Is it below the TB like on an L98? This is likely where I would go next, but the LT1 troubleshooting tree would be real helpful folks!

LT1 guys, what is the importance of the AC high pressure switch not causing the fan to come on? What is common to the ECM ground to the fan relay and the AC high pressure switch to the fan relay? Is is only the ECM or is there other items to be checked?

I'm thinking it's time to bring this one to the shop as the owner does not have the manuals or equipment to work this.

Pete

R Cook 92

I do have wiring diagrams of my fans... And plenty of voltage testers, and test lights to check all the wiring, I was just curious if it was indeed a wiring problem, or more accuratly, if anyone had had a similar, or same problem.

I'm quite sure that the radiator is unobstructed... And the car is never driven in winter or cold months(for the above post)...And the coolant is just fine, although I will go back to the green, since I'm reading GM doesn't recommend it in pre 94 vettes... but the cooling was just fine until the fans wouldn't kick in, I'll look for a common between the CTS, and a/c high pressure switch...

Thanks,
Randy

PeteL

Randy,

I'm concerned that the AC high side switch does not cause the fans to come on. This is usually a two wire sensor. It would be worth finding this, if it is in your preliminary manual and see how to test. Probably pulling the wire and shorting the leads together on the wire should cause the ecm to command the fans on. I would find this test and check. This should tell you if the ecm can control the fans based upon this sensor input.

Remember the ecm is turning fan on when you short A&B on the ALDL.

If the fans come on with the AC test, then the high side switch could be bad or your AC is not building enough pressure - but this is not the entire problem.

If the AC switch test turns the fan on, I would move to the CTS. On an L98 there are seperate CTS for the guage and for the ecm. I would amagine this is true for the LT1, but maybe not. If you have access to a scanner, you could just see what temp the ecm thinks the car is running. If no scanner than you need to find the ecm coolant temp sensor (below throttle body on L98), and test this sensor with an ohm meter. The manual should have the normal range vs. resistance (measured in ohms). If this sensor is also bad then the ecm may think the engine is cold and not turn on the fans.

If this sensor test good, then it's time to find out why the ecm is not turning on the fans when the temp is high. When you shorted A&B together on the ALDL and turned on the key, did you get a code 12? Where any other codes present?

vettenuts

Randy/Pete,

A couple of months ago there was a tip in the magazine published by the NCM. It discussed disconnecting a swtich on the AC such that the fans would run full time. Don't know if it is available on-line, but you might e-mail them and ask. I will look for the article when I get home.

df5152

sounds to me like ur fans Are not coming on. While the car is staionary there is no air going throught the rad. when u drive air flows through and it cools. this si why the drive to the buriito shop cooled ur car and y when u stopped it heated back up again. This does not mean that what everyone else said may not be part of the problem too.

PeteL

Ray Zavorka

vettenuts

Found it, it was in the December 2000 issue of America'a Sports Car. Tip is written by Jerry Watts:

C4 Radiator Fans

"If you would like for your radiator fans to run constantly even when the air conditioner is not on or is not up to temperature, you can disconnect the small switch on the small air conditioning line on the passenger side of the engine. This is the one that goes back to the hearer case (the back switch of two)."

R Cook 92

HA HA HA!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!

I FIXED IT!!!!!

I went out this evening with my wiring diagrams, and all set to start looking for pink wires with white stripes, bad connections...etc. I started with the A/C switch... And when I got done( it wasn't that...) I looked for codes....I got a 66..which is because I unplugged the sensor... Well, while I was in diagnostic mode, I could hear what I always thought were my fans... So I got out of the seat and went to look at my fans running. Well, I look, and they're not running. So I remembered what I read here... and if they didn't run on the AB jumper, it could be relay... so I grounded each relay.... and the fans kicked right on!!! So I ran on up and got 2 relays, now it wont idle abouve 200!!!!!

I can't thank you guys enough!! I was clueless when this all started...

Any of you ever come on through St. Louis, let me know, Drinks are on me!

Thanks ALOT!!!
Randy Cook.
cool, 92 auto coupe

PeteL

Very good, Randy. Very good.

GlockLT4

Congrats! I know how much of a pain in the *** electrical connections can be, trust me . Glad ya got her fixed!

vettenuts

That's great. Hope everyting turns out OK.