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Gentlemen,

Drove 100 miles today at 65 to 85 mph. No issue while the 18# pressure cap was installed. I continue to notice some vapor along the outside of the cap, as though it continues to bleed off pressure while I am driving. My question remains, what could have changed or why is the pressure continuing to be so high? Would it be due to a slight obstruction? Could it be from one of the 17 year old heater hoses collapsing? Could it be due to the 50/50 mix being off?

Thanks in advance!

Ohio Jim

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We have seen tanks crack and leak under pressure, look closely at the tank for cracks and and steam under pressure. Check the flange where the cap attaches for dirt, gunk that may hurt its sealing.

The 98 I am having coolant loss on also has a 15 lb cap, I may change to 18 lb also. The manual calls for an ac delco rc-33 but I can not find the specs

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Body by Fisher,

I have had the tank our twice in three weeks. I have tested it cold and hot at 15-17.5 pounds. I continue smell the coolant when I exit the car. When I open the hood, the previous cloud of coolant is gone, but the top of the rim around the cap is wet, sometime just moist. I wash off the area every day and the moisture or wetness returns. Right now I can live with it because I cannot detect any loss of coolant. Currently I am trying to get an accurate reading on a Brix 20 gage by converting my sample to be read by the gage 'cause I am too cheap to buy a Brix 50 gage. I am waiting for Rock Auto to deliver the new 18# cap. The number is RC-38, I believe. I could not find the cap under the 1999 model year. I ended up using the AC Delco # 25713160 on the Rock Auto web sight. It is listed at 18#. that is SAE 16-20 pounds, per the description. I continue to not understand what brought this on. I am figuring it is age related, but what can I actually do to reverse the aging of the cooling system without replacing all the heater hoses?

Thanks,

Ohio Jim

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Ok, you gave a hint, you smell coolant, now that may not be your main problem, a leaky crossover seal, heater pipe rust through, or radiator end tanks could give that to you. Keep in mind that you may not actually see coolant leaking and you are NOT going to SEE cracks in the tank, radiator end tanks, etc. If coolant leaks under pressure, it will vaporize when it hits the atmosphere, but you will smell it. I just disassembled a 98 NS and the two heater pipes were rusted through. Ill post a photo its on my Android.

If I recall, you have pressurized your cooling system correct? Pump it up to 18 to 20 PSI and look it over for leaks, you have to be leaking somewhere if you smell it. The water pump is attached to the 'crossover'. Facing the engine from the driverside, the crossover has 4 seals, 2 on the left (left head the block) and 2 on the right (right head the block). These seals are famous for deteriorating, see this crossover seal, it came out of an engine that was 'remanufactured' in 2006, the 2 bolts were loose and the seal fell apart in my hand.

20151114_193548_zpsxzqrdqiz.jpg

Something is going on by your tank, again keep in mind that it may leak UNDER PRESSURE, as steam. We have seen coolant tanks and radiator end tanks crack.

Look closely at your radiator end tanks, if they are leaking, you will see a white chalky deposit. Did you pull your waterpump?, the pump body seal can leak look below the pump pulley area for evidence of leaking, streaking or white

As far as the 50/50 mix, get a tester and make sure it is at least 50/50, see the chart below look at the difference in boiling point between 50/50 (265) and 25% (252)..... spontaneous boiling will expel coolant but usually you can hear it boil. The chart is very useful in helping you reach your desired coolant concentration percentage.

It sounds to me that you have it solved with the 18 lb cap, you are smelling coolant but that only means that you have a leak someplace.

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Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Ok I just noticed in your previous post that you said the tank is leaking in "steam puffs".

BINGO!

Read what I wrote above. Cracks release at a given pressure and will vaporize when it hits the atmosphere as steam.....

That crack is setting an upper limit to the pressure your cooling system is capable of holding as it releases pressure when the specified pressure is reached. Not only are you losing coolant but you losing pressure which can cause it to boil at a lower temp.

Take a good look at your tank, its probably cracked.

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Body by Fisher,

Thanks for the summary. I think I get it now. I will first move on being sure the concentration is accurate at 50%. That may solve the coolant I see vaporizing/leaking around the cap. I need to then attack the leak again. I have never replaced the water pump, consequently the seal behind it and the crossover seals may be toast as well. Nothing lasts forever. Thanks again, and good luck with your '98.

Ohio Jim

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Body by Fisher,

I just received your latest post. I will go over the tank once again. There is wetness around that cap, but I could not see where it's coming from. I figure it is being released because the pressure is STILL over the rating of the cap. I know the top surface finish of the tank lip feels fine, so I did not want to go after it with emery cloth and deteriorate that finish, or remove any coating which may be on the plastic. Friday I may have to run into Cleveland at high speed again, so I will see if that coolant in the return line acts like it is boiling. Last week when the car overheated, the surge tank return line was boiling coolant inside. I could feel it when I squeezed the line.

Have a nice day tomorrow!

Ohio Jim

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I have used uv dye added to the coolant to find small leaks that are not visible. Just go to any auto parts store and get a bottle of yellow dye, usually you can get a kit with the glasses and the ultra violet flashlight that will make seeing the dye easier.

After adding the dye drive for a few days. Any where the coolant leaked either as a liquid or as steam will leave the dye behind as a tell tale sign. Look at the obvious places, like the radiator end tanks. Heater hose and connections. Coolant crossover

That should make it pretty painless to find your problem.

As body by Fisher stated if there is a small crack or leak anywhere as soon the coolant gets out to atmospheric pressure it will turn top steam due to lower boiling point. At 15 psi a 50/50 mix boils at about 260-275 degrees F. With no pressure coolant will turn to steam at any where from 195-220 degrees.

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