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Good evening everyone,

My daughter is the proud owner of a 'new to her', '99 Deville, with 140,k. Today it got up to 220 degrees before she turned it off and added water. I found passenger side mat wet. She said 'smoke' came out of the vents. I am figuring heater core leak. For the short term is it possible to clamp off both heater core hoses until we can get the core replace? If not, must I place a jumper to keep water flow to those two hoses? Is it the top or bottom hose which flows into the heater core? I see one hose is coming off a tee, so I am hoping I can place a clamp on both hoses so she can continue to go to college this week, while I gather the parts. Please advise... Thanks in advance!

Ohio Jim

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Hello,

Simple question... Does anyone know if I can clamp off the inlet and outlet to the heater core on a "99 deviille for temporary driving? Thankx Ohio Jim

What "I" would do is get a short piece of pipe or tubing the right size to fit in the ends of the hoses.

Use a clamp on each hose to secure the pipe.

Then the water is still circulating, just not thru the heater core.

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Thanks Jim!

Upon further investigation, I found the collant on the floor mat likely occured when the radiator cap was removed under an overheat condition. Coolant appears to have entered the vents near windshield. Drove car 15 miles and no coolant hit the mat. Now I am trying to ascertain what caused the overheat condition. Coolant level was not verified when car was purchased. Low coolant light came on a week later and some collant was added. Sunday the car overheated. It appears to have lost 1/2 gallon coolant over 15 miles. My first thougth is dreaded head gasket. Need to verify. Only way I know is to get some load on the motor and see what temperature does. Last night it never climbed past 225 degrees on level roads, at 15 mile trek. I verified the coolant bypass tube to the cooant tank is passing coolant, so water pump is working. Any additiional thoughts?

Ohio Jim

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Thanks Jim!

Upon further investigation, I found the collant on the floor mat likely occured when the radiator cap was removed under an overheat condition. Coolant appears to have entered the vents near windshield. Drove car 15 miles and no coolant hit the mat. Now I am trying to ascertain what caused the overheat condition. Coolant level was not verified when car was purchased. Low coolant light came on a week later and some collant was added. Sunday the car overheated. It appears to have lost 1/2 gallon coolant over 15 miles. My first thougth is dreaded head gasket. Need to verify. Only way I know is to get some load on the motor and see what temperature does. Last night it never climbed past 225 degrees on level roads, at 15 mile trek. I verified the coolant bypass tube to the cooant tank is passing coolant, so water pump is working. Any additiional thoughts?

Ohio Jim

Most good auto stores have a HYDROCARBON TEST KIT to test the coolant for the presence of exhaust gas.

You rent the kit and only pay for the test fluid.

The car need to be drives some AFTER coolant is added or you may get a false negative reading.

The coolant bypass hose will, over time, mix the new coolant with the old.

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Texas Jim,

Thank you for the detailed response. I drove the car today. I removed the radiator cap at 158 degrees,and found no evidence of bubbles in the overflow tank. Temperature remained between 212 and 226. I was doing starts and stops in 45 mph zone. After two trips out, I found the car dripping coolant just behind the pssenger side front door. It felt as though the coolant was running down the seam under the door. The newspaper I had placed over the floor mat up front was wet, so I 'think' it is leaking at the heater core. My plan is to verify the leak and replace the part. I see there are some detailed instructions available for reference. I will post as I go forward.

Thanks again!

Ohio Jim

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Ohio Jim, If I were you and there is any chance of returning the car or having repairs paid by sales persons, the very first thing I would do is the hydrocarbon test as suggested by Texas Jim. I would hope it comes out negative, but in the case that it didn't that would most likely change your future expenses and repair direction. My car would go up to two months between "spells" never getting hot or giving indication of problems. I could easily have sold it during those times. I believe if the head gaskets were bad the engine builds excessive coolant pressure that is hard on all parts. (radiator, heater core etc..) A very small charge for the test to help you in your direction of maintenance/repair. I am the proud owner of a 99 sts and hope your daughter gets to continue as one :)

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Airmike,

Thanks for the reply. It was a private sale. Contacted previous owner, claims he knew nothing. Today my daughter talked to a 'mechanic' at school. He comented on the nice Deville. She mentioned the leak. She said it might me the heater core, however, he said don't rule out some kind of leak caused by the air conditioner line under the hood. I have her trying to contact him now so we can speak. He mentioned coolant running down the frame rail. When I found the leak outside the car yesterday, it was dripping off the frame rail just behind the passenger side door(!). Any thoughts?

Thanks

Ohio Jim

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Welcome to Caddyinfo forum.

The answer to your first question would be a definate no for me. It is crucial that the coolant flow properly throughout the whole system. I have a writeup around here with detailed pictures.

If it has dual climate control(only equipped on floor shift models, IE concours, deelegance) it will be slightly more difficult, but either way it is not at all difficult. 35 minutes tops if you have done it before. maybe 1 hour for a first timer. My biggest recommendation is to unhook the battery while you do it. Once it is done hook up the battery, turn the key on and dont touch any buttons for at least 1 minute, This will allow the computer to relearn the vent positions.

I hope you dont have a problem with the engine and it is just the heatercore. I would definately not let it go as it could cause more problems.

Also another tip. I recommend getting a solid aluminum heatercore rather than getting the one with the plastic tanks. They have a tendency to crack and seep causing headaches. Last one I bought was about 45.00 for a good one

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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It's normal for clear water to drip on the passenger side about as far back as the door hinge and under the car about a foot when you stop or park the car, summer or winter, because the A/C uses the cooling to keep humidity inside the car down even when you aren't using A/C (unless you press the <Off> button, which isn't recommended at any time except when the alternator light comes on). If it's clear and has no smell, it's from the A/C drain and it's normal.

If it has a coolant smell, it's from the surge tank overflow tube. That usually is a foot or two farther forward from the A/C drain puddle and *will* have a coolant smell. Coolant water will be colored according to the antifreeze you use (red, orange, yellow - but please, not green).

If it's from the overflow tank, it isn't a heater core. If the water in the cabin came through the vents and all you see now is outside the cabin, I would let the heater core alone until you solve the overheating problem. If the heater core is leaking, that will show when you are working on the cooling system through a pressure test.

One very important thing that hasn't been mentioned yet is the antifreeze percentage in the car. Northstars (and nearly all modern high-performance engines, which is to say essentially all newer engines) need a 50-50 mix for proper cooling system operation. This is because the boiling point of the coolant at 15 psi pressure is high enough to prevent steam bubbles inside the head during normal driving conditions, but if there isn't enough anti-freeze steam bubbles *will* form and occasionally cover the thermostat temperature sensor for a few seconds, causing a flash overheating episode. Have your antifreeze tested. It must be at least 50-50 but not more than 70% antifreeze (too much antifreeze adn the boiling point decreases again!). 50-50 is ideal.

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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Whether the heater core will turn out to be bad or not, I will just mention that I replaced mine a few years ago after it cracked. There is a step-by-step description of the procedure here:

http://caddyinfo.ipbhost.com/index.php?showtopic=28646&p=167025

with a link to pictures a took during the job. My car is a '97 DeVille (and it has dual climate zones like a believe all DeVilles of that vintage had).

Just a few words on coolant: like mentioned, 50-50 is ideal, and you should never decrease the amount of antifreeze (DexCool or whatever you use) below that for three reasons: the freezing point would go up, the boiling point would go down and the concentration of corrosion inhibitors would go down. If the concentration of antifreeze is increased, the boiling point will go up (also above 70%). The freezing point, however, will start to increase again when you increase the amount of antifreeze too much. The increased risk of coolant freezing and the lower heat capacity of antifreeze compared to water are the two reasons not to increase the antifreeze concentration above 70%. To absorb the same amount of heat, ethylene glycol (antifreeze) would increase its temperature more than water, meaning that the temperature difference of the coolant that entered the engine and the coolant that exited the engine would be greater. In other words, the cooling system would be less efficient. This reasoning holds as long as we assume that there is no boiling taking place in the hottest areas of the engine (if boiling does take place, it would be reduced by increasing the amount of ethylene glycol, which would increase the cooling system efficiency).

Here is a good web page about ethylene glycol for cooling systems: http://www.engineeringtoolbox.com/ethylene-glycol-d_146.html

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I have freezing temperature versus percentage of ethylene glycol, plotted from numbers off a Prestone gallon bottle for Caddyinfo in January, 2007. I just looked again and have both curves, including boiling point; I recall not being able to find information on boiling point at the time.

Anitifreeze_Freezing_2013.jpg

Anitifreeze_Boiling_2013.jpg

Source for freezing and boiling temperature versus percentage of ethylene glycol:

http://en.wikipedia.org/wiki/Ethylene_glycol

I used a simple rule-of-thumb for pressure, 3 degrees F for every psi of pressure, for the 15 psi boiling point curves; they are simply 45 F higher in temperature than the curves from Wikipedia, which, presumably, are for atmospheric pressure.

This is presents yet another reason to keep a light throttle when the engine is cold. Asking for a lot of power when the radiator pressure hasn't built up is more likely to form steam pockets in the head which will need to be bled off with the thermostat closed to keep the cooling system working properly.

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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WOW!

Gentlemen, you are truly amazing! I cannot thank you enough for all the help! I may get through this afterall! I was able to pick up a new, all metal, heater core today for $44 - 40% at Advance.

Rockfangd, no daul zone, so that should make it easier. Thanks for the detail regarding the unhooking of the battery. I read some internet instructions which warned not to set off the air bag. Basically, saif to unhook the battery, remove the air bag fuse, turn the key on, and then unhook the wires to the airbag! I thought if i unhook the battery, it would suffice... I don't mind pulling the fuse with the key on, if you think it is necessary. Please advise...

Cadillac Jim, I had NOT thought of the pressure test... EXCELLENT IDEA! I will get a kit and verify the source of the leak. Regarding the percentage of anti-freeze, I had always heard the refractometer is the most accurate method. Do you know how I would determine the refractometer reading for 50% anti-freeze? Does anyone have this information?

Thanks in advance,

Ohio Jim

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The instructions for using the refractometer should be on the device, or come with it. They aren't cheap. Here's one on Amazon for $45 + tax, S&H:

http://www.amazon.com/Robinair-75240-Coolant-Battery-Refractometer/dp/B000HTNODE

You can also look at your local Sears, Pep Boys, NAPA Auto Parts, etc.

As I recall vaguely, you look through the fluid in a tube that includes antifreeze and a prism, and see where a line is relative to a scale, where you read off freezing point or percentage antifreeze, depending on a scale.

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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I think that all of the '97-'99 DeVilles have dual climate control. I may be wrong on that one, but I am quite sure that both the base model and d'Elegance had column shifters; only the Concourse had a full center console with floor shifter. I am 100 % sure that there are base model DeVille's that combine a column shifter with dual climate control, since I have a base model '97 DeVille with both. The passenger side temperature is set with a knob that is located on the passenger side armrest, and it is not set in absolute temperature, but rather as an offset compared to the standard temperature that is set on the main climate control. In other words, even though the car has dual climate control, there is only one temperature that is set as a number and displayed on the dash. There are also no separate controls for the passenger temperature zone on the dash -- only on the passenger side door armrest. So it would be possible to have a look on the dash and think that the car does not have dual climate control, even though it does.

The passenger side control knob can be set up to four notches (each notch representing one degree difference) lower or higher than the "standard" temperature, for a total of nine settings (including the middle setting -- no difference). It can be turned on and off by pushing the knob. When on, there is a little dial that lights up on the knob. The standard temperature (or turning the dual control off) often results in slightly warmer air on the passenger side, which makes sense since the driver is more active than the passenger(s) and therefore normally prefers a slightly cooler temperature. This only happens after the car is in good control of the temperature -- when starting on a hot day, it will of course blow full cold air, and when starting on a cold day, it will blow full hot air on both sides until the temperature approaches the set one.

Either way, I think that it was quite doable to change the heater core even with dual climate control (see the link in my previous post). The hardest part when I did it was to remove the two hoses that go from the engine to the heater core. What makes it much easier on these cars compared to many other cars is that the heater core sits on the passenger side. If it would have been on the driver side or behind a full center console, it would have been much harder.

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All,

Well thanks for all your help and support. My son met me at my daughter's house and changed out the heater core today. (And I helped...LOL) It went rather smoothly. We were forced to break off both the inlet and the outlet, as we were unable to twist the hoses loose. Entire job in less than two hours.

Ohio Jim

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The final victory is driving the car an noting that the problem is solved and everything is working OK again. Please post when you can announce final, absolute victory.

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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That is correct on the dual zone climate control. I do apologize. There is a knob on the passenger side door. On the 96 it was only available with console shift and it was on the climate control display. Same with the Seville and Eldo. The 97 Deville started with dual climate control on all along with quite a different interior.

Glad you got it changed out and I hope it helps

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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Cadillac Jim,

Absolute Victory!

Rockfangd,

No apology necessary. The daul control really did not make it any harder, I just had to recognize what the second 'rod' was for!

Gentlemen,

It appears as all is well in Deville-ville once again. Absolut Vic We drove it for two days and detected no drop in coolant nor dripping. I will keep and eye on it as we expect to drive up to Michigan on Saturday.

Thanks to all for your help!

Ohio Jim

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