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Trying to figure my 1996 Concours out I just bought 91,000MI


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I bought a 1996 Cadillac Concours with 91,450 miles on it in prestine condition (Body and Interior wise) ALMOST LIKE NEW. My Check coolant light has come on twice in a 10 day period requiring 1/2 gallon of antifreeze first time 10 days later needed another 1/2 gallon. I replaced Radiator cap just because i took it off and like the flow-vent type caps..I also notice what looks like a "cooper flake" reside on bottom of radiator cap that looks like someone threw "stop Leak" in the car. Im trying to figure out why and where my coolant went mind you the car runs fine but Im really anal retentive..
at regular Idle 190F
At regular idle after Highway travel 201-210F

With Air on

at regular idle 201F
At regular idle after or doing Highway travel or traffic 213F to 222F

Never seen it above 233F and that was only after I got off highway and stopped at service station to fill up and went to restart it.

My inquiry is what are the symptoms for the head gasket issues i keep hearing so much about? does stop leak work for it ? or should i just enjoy the darn car while its running perfectly and stop worrying about quirky little stuff??

Thank You for your Advice, comments, and recommendations

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The first thing you should do is have your coolant tested for combustion products. That will rule either diagnose head leakage or rule it out, and either way you will have a solid basis to plan.

If it does *not* have head leakage, you should change the antifreeze (use red) and oil, check the belts including the little on on the rear of the engine that turns the water pump, and check the hoses. You can look for the coolant leak when you change the antifreeze and check the belts and hoses.

Also, check the levels of the brake fluid, transmission fluid, and power steering fluid.

Run the OBD codes, write them, down, and post them here. You can get instructions from a link in my signature block. With the OBD codes, we can tell you what maintenance items the car can use. The experience of reading the codes will prepare you for doing it again as the first step in diagnosing anything that might need fixing in the future.

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-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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I think adding coolant when low coolant light comes on is not being anal. But, a newly purchased car which requires 1 gal of coolant in 10 days time is not good.

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You don't say where you bought the car, but if it was from a Used Car Lot, you should get it back under warranty right away. If from an individual or purchased "as is", you've got some work to do. First thing is to find out where that antifreeze is going. Some of the things we've seen on this board are:

Plastic Coolant tank

Heater core

hoses

Metal coolant pipes behind the engine rusted out

bad radiator cap

radiator end tanks (plastic)

:welcomesmiley: Welcome!

Never underestimate the amount of a persons greed.

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NO ODB CODES My "Service engine soon" light poped on last Tuesday but correctd itself Wednesday morning I did pull the codes though when it popped on P0139 - O2 Sensor and then it had two stored unrealated CM codes one was RF xxxxx - Incorrect RF transmitter code and the othr one referenced the security system.
Car was bought of my uncle who is a used car dealer i only paid $1600 for it. and like i said drives beautifully no noticable issues other than the light that poped on Tuesday (mind you it still has same gas in it that it had on lot and apprently has been drivin in 6 months) I just top the tank off and drove it from Philadelphia, to VA without any issues its just the Collant thing and the fact it has popped on twice is puzzling me i usually take extremely good care of all my vehicles. Dry has a bone underneath he vehicle has well 1 owner car prior to me.

By the way the cooling system looks new ...the top and bottom radiator hoses are new and so is the little coolant hose that underneath the housing to waterpump.... (im very mechanially inclined :) not just pretty LOL)

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Go by your local autozone or O'Riellys and rent the "Combustion Byproducts Test Kit"

Follow the instructions and post the results back here.

Do not do the test if you have just added coolant.

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ill check it out when i get back home next week.... i travel a lot

Im one of those peoplewho like to go or prepare themselves or worst case scenerios like the headgasket thingie.....

but other than the coolant particles and the check coolant advisory light the car is flawless and im not that lucky tohave boght such a nice car for so cheap....Momma knows betta!! LOL

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By the way the cooling system looks new ...the top and bottom radiator hoses are new and so is the little coolant hose that underneath the housing to waterpump.... (im very mechanially inclined :) not just pretty LOL)

There's a clue. Unless you've already changed these items yourself, somebody has been looking for leaks in the recent past and changed a few parts.

Find out where the coolant is leaking.

Here's how this works. If it's a head gasket leak, it will be a pressure leak from the cylinder head into the water jacket. This gas is permitted into the water jacket in small amounts, but under great pressure. If you are driving a long period of time, more and more gas is accumulated into the cooling system. As the pressure gradually builds, it eventually will force itself out of the weakest point, so any small leak will become apparent. If there are no leaks in the system, the radiator cap will eventually blow off the pressure as it is intended to do. GM has taken steps to eliminate any air (or small amounts of combustion gas) from the cooling system, this is called the bypass hose. It runs from the top(?) hollow bolt in the throttle body, under the manifold cover, and into the top of the plastic coolant tank. If there is no air in the system, a steady small flow of water will be coming out of that hose. That is provided that someone hasn't plugged it up with tiny copper flakes or someting else. Check to see if it's flowing when the engine is cold and first started. No flow? Clean out the hose and the bolt. Don't blow air into the bolt, that will only save the plug for another day.

The good news is, a head gasket leak can easily found be by renting a combustion gas test kit from your local Auto Zone store. The test sniffs the fumes in the coolant tank and turns greenish yellow or yellow if it is bad. Get the kit. If the test fluid changes color, give the car back to your uncle.

Never underestimate the amount of a persons greed.

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THANK YOU ALL
and Johnny G GOOD POINT I havent had the time to do anything to the car I just drove it back and sorta parked it in the drive way....I know better, I should at least do some preventative maintenance before jumping conclusions, like drain and flush the cooling system just for General Purposes then ? or at least a drain and refill Correct?
I mean even if it has a bad headgasket (i will pay to replace it or drop another crate Northstar engine in it) It is worth it just body, interior,trans, suspension and steering system wise.
he aint getting it back (No take backs) LOL
Besides i spend $1600 on dumber things that do absolutely nothing

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Thanks.....
Although im sure a few people ive dated would disagree with you! LOL
(Kidding)

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No, you should NOT change the coolant or do other diagnosis before testing the coolant for combustion products, because the combustion products test is cheap, fast, easy, and conclusive. If it is positive, you save all that time and money for flushing the coolant, buying antifreeze, etc. And, you know for sure exactly where you are.

If you drain and flush the coolant, you have to drive the car for a week or so before a coolant test will tell you anything. And, you will have to do a coolant test anyway.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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THANK YOU.

I would not have known thoe facts i would of drained and flushed coolant then did the test not knowing i would of screwed upth results. Ill do the test first thing when i return home next weekend

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I have said it before and will say it again. The 96 Deville was the best model of the era to me. It had the best ride, most room, good features, excellent reliability, you name it.

Glad to see you are willing to fix it. I will be honest weeing all of the new parts you mention would worry me a little. Back when I bought my Seville (97) it had a bunch of new parts that a dealer had installed trying to resolve a mysterious loss of coolant. by the time all of the money was spent on all the repairs it could have paid for the head job it needed. Oil looked like chocolate milk. I had it done and never thought about it again

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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99EldoETC, thank you for posting the videos. I was confused about the stud repair, but Tim Carrol's (other) videos cleared that up for me. As they say, a picture is worth a thousand words.

As it turns out, the studs are not true studs in the pipefitters sense (my once upon a time background) but more of a timesert without the sert. It also appears that the outside thread pitch and diameter of the end that goes into the block is pretty darn close to the sert part of the GM prefered repair, which makes sense. My old school knowledge always told me that a stud actually had a nut on BOTH ends of the bolt.

If Ms. Princess needs to have her engine repaired for HG failure, this would likely be the way to go. Just fewer moving parts to mess up during installation, and less "give" during future heat/cool cycles. Personally I'd use red thread locker though.

Never underestimate the amount of a persons greed.

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AGREED ON THAT ONE.....

99EldoETC, thank you for posting the videos. I was confused about the stud repair, but Tim Carrol's (other) videos cleared that up for me. As they say, a picture is worth a thousand words.

As it turns out, the studs are not true studs in the pipefitters sense (my once upon a time background) but more of a timesert without the sert. It also appears that the outside thread pitch and diameter of the end that goes into the block is pretty darn close to the sert part of the GM prefered repair, which makes sense. My old school knowledge always told me that a stud actually had a nut on BOTH ends of the bolt.

If Ms. Princess needs to have her engine repaired for HG failure, this would likely be the way to go. Just fewer moving parts to mess up during installation, and less "give" during future heat/cool cycles. Personally I'd use red thread locker though.

I would even try my best to let him do it by having the car shipped to him (my installer here constantly complains to me about my other cars taking 2-3 days to fix and occupy his bays...

and the Ms. isnt neccessary I work for living LOL officers are called MS. and MAME...

Edited by princess
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I did the "Combustion Product Test" and the fluid stayed blue I asked the guy at the autoparts store to double check me so I DO NOT HAVE Exhaust gases in my anti freeze :)
Off Topic question, Are any of the rear brake lines in a 1996 Cadikac made of rubber? or rubber looking like kind of tubing?

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When performing the combustion test, it is important that no new coolant was added. If so, it will result in a false negative.

There are rubber brake lines at the rear - they are short lines to accomodate the rear suspension movement and are right at the calipers and are about a foot long. The opposite end of the rubber lines connect to steel lines.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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The flexible brake lines from the calipers to the frame are special ultra-high-pressure tubing made especially for that purpose.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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