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Far chance it could be a bad water pump, like the impeller came loose of the shaft. And then the overheating would expel coolant.

That's happened to me. At low rpm the pump would be ok. At higher rpm the shaft would slip on the impeller and car would over heat

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Kevin,

Thanks for your reply. Yes I plan to re-test the coolant system. I did it last Sunday morning cold for three hours. It started at 15 psi and ended at 14 psi, so I figured it was not a head gasket. I did pull the purge line last weekend as well, and it had good flow. I will pull it again tonight before I leave. Funny how I did not have any heat in the car when the car was overheating today. I added a half gallon of water at 7pm and took it for a 5 mile quick cruise. It came up to temp and stayed in the center of the gauge. I could feel the heat coming from the heater because I had left the heater on full blast when I parked it at 3:20 pm.

Jwoods,

That's what I was trying to determine. I have changed a few of these water pumps and I do not know if this style would allow the impeller to come loose or not.

I guess I will give it another go on the way home tonight. I thought I'll get a diagram for the heater hoses and possibly back flush it this weekend if I don't have any luck finding a leak after pressurizing it cold.

I added the coolant tablets in powder form last year when I pulled the radiator to replace the alternator. This week I added two tablets again because I had pretty much boiled out most of the coolant. I can't imagine that would give these issues.

Thanks Again Gentlemen!

Ohio jim

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Kevin,

Oh Ya! I forgot to mention the Dexcool has been replaced twice this week, so I didn't want to get a false reading on the combustion gases.

Ohio Jim

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No the tablets are not creating the problem.


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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I am finding this thread very interesting as I mentioned I am working on a 98 that is losing coolant and was overheating at the end of the summer.

As you, my combustion by products in the coolant test was negative. Iv done it twice. There is no major source of a coolant leak.

Their starter just crapped out so I will be pulling the intake and will get a closer look at the engine and pressurize the cooling system.

This may have been asked but did you look the water pump belt and pulley over carefully? I recall the guru mentioning that overheating on acceleration can be caused by a slipping belt.

Jwoods, that is the first I have heard a water pump fail that way. You have seen that happen on a NS pump?


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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Jim,

Remove the water pump belt shield and put a 1/4" breaker bar in the square hole and make sure the tensioner moves freely. If the tensioner is frozen up, the water pump belt will not be tensioned properly and will slip on the pulleys. If the belt slips the water pump will not turn the correct speed.

Bruce,

Should the portion of the '99 STS overheating be moved to a new thread?


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

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Gentlemen,

I am about to remove the shield on the water pump belt. I had that thought yesterday while i hope we were all enjoying our Thanksgiving. I believe the cam seal is leaking on that shaft so I was wondering if the belt was slipping. The tensioner and belt are two years old. I will then go rent the coolant pump and check for leaks much better than I did last time. And it's starting to rain...

Ohio Jim

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Guys,

Pulled the cover on water pump drive. Belt and trainer appear to be fine. No oil to speak of from the cam. I question the flow to the surge tank. Every time I have checked it, it flows but is gurgly. It didn't come out hard when I reved the engine like I thought it would. There is definitely flow. Off to get the pressure tester.

Ohio Jim

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Gentlemen,

About 2 hours with 15 psi pumped into the system cold. Lost about a half pound of pressure on the gauge. Cannot detect the leak. Will now relieve pressure and start up cat to see how much pressure it builds and if I can find the leak.

Ohio Jim

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Gentlemen

I have it up on stands. Idled up to normal operation temperature. Giving it gas to 20000 rpm. All is acting normal Cannot detect any leaks. Only problem is the pressure on the gauge attached to the purge tank worked its way up to 17 psi and is staying there. No wonder the purge tank keeps blowing off steam with the 15 psi cap! What causes the pressure to rise? What should it be? It stayed at 13 psi for quite a while then Started to rise. Fans cycle on and off like normal at just over 1/2 on the temp gauge. Temp comes right back down to half. 30 minutes in, pressure 17.5. Going to shut it off. Do t know how much it can take.

Any thought?

Ohio Jim

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When I bought my dts someone had put in a cheap water pump and it separated from the shaft. The replacement I bought does not look like it can come loose.

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Jwoods,

This is the original water pump as far as I know. I bought the car with 38,k on it and all the hoses were original. I took it into town and it newer went over the middle of the gage but it still over flowed the purge tank. From what I saw today with the gage on it, it is building pressure which is causing it to overflow. Is there any other way to build 17+

Pounds of pressure without having a blown head gasket?

Ohio Jim

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Is there any chance you're overfilling the surge tank with coolant? The full cold level is 2-1/2" below the neck. If the surge tank is overfilled, it will overflow out of the tank when the system builds pressure.

If the coolant is to the correct level, pressurize the system and leave it pressurized overnight. The next day, remove the spark plugs, unplug the ignition control module and crank the engine over - check for coolant from the spark plug holes. If there is coolant, the headgasket(s) are shot.

You can also fabricate a spark plug air adapter by breaking the porcelain out of an old spark plug so only the metal threaded portion is left. Tap the center for a 1/8 pipe thread, then use about an 8" piece of pipe with a male air line fitting attached. Remove all 8 spark plugs and the surge tank cap. Use a wood dowel down the cylinder #1 and rotate the crankshaft with a breaker bar on the balancer bolt to bring the piston to top dead center, then thread the adapter into cylinder #1, connect the compressor air hose to the adapter and pressurize the cylinder to 120 psi. You may need to keep tension on the balancer folt to keep the piston at TDC and all valves for that cylinder closed. If you see any bubbling in the surge tank, the head gasket is leaking on that cylinder. Repeat for the remaining cylinders.

Below is a spark plug/air adapter I made several years ago.

post-45-0-39650100-1448722523_thumb.jpg


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

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Kevin how is the copper tubing connected to the spark plug? Threaded?

In the description of pressuring the cylinder how tricky is it to keep it at TDC when pressurized without accidently kicking the cylinder down? Does it pressurize 100% of the time? I suppose it would be prudent NOT to leave a socket/breaker bar attached to the crank bt when pressurizing or pressurized, for safety sake?


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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You could also borrow a leak down tester from a car parts store. It threads into spark plug hole and had a valve you connect to a air compressor. Then you tell if cylinders are leaking anywhere.

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Kevin how is the copper tubing connected to the spark plug? Threaded?

In the description of pressuring the cylinder how tricky is it to keep it at TDC when pressurized without accidently kicking the cylinder down? Does it pressurize 100% of the time? I suppose it would be prudent NOT to leave a socket/breaker bar attached to the crank bt when pressurizing or pressurized, for safety sake?

Yes - it is threaded. I think it is an 1/8" pipe tap.


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

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Kevin how is the copper tubing connected to the spark plug? Threaded?

In the description of pressuring the cylinder how tricky is it to keep it at TDC when pressurized without accidently kicking the cylinder down? Does it pressurize 100% of the time? I suppose it would be prudent NOT to leave a socket/breaker bar attached to the crank bt when pressurizing or pressurized, for safety sake?

The pipe is connected to the spark plug via a tapped connection. The pipe looks like copper but it is an 1/8" pipe from the plumbing section of Menards. I Loctited the connections so they would not come apart when removing the adapter from the engine.

If I recall correctly, the crank will rotate when a cylinder is pressurized - I left the breaker bar in place and wedged it so it wouldn't move. A flywheel lock could also be used but it is more work.


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

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Gentlemen,

Thank you for the lively discussion. There is just too much knowledge and talent among you to quantify! Kevin, Yes I was overfilling in and effort to get a little further down the road. I ran the car with the pressure tester on the system at idle and then 2,200 rpm for quite a while on Saturday with the car in the driveway. I was unable to close the hood with the tester in place. My son called to see how it was going and I explained the situation. He schooled me on the need for the level to be correct to allow for expansion. Long story short, he pulled off the road, and read his cap was rated at 18 psi, on his '01 STS. I had just replaced my cap again with one from Napa, rated at 15 psi. (Dumb @#%!) It became a Eureka moment for me. I borrowed the 18 psi cap today and drove it to work without an issue. Once it cooled, I verified the level was 2-1/2" below the neck, just where I had set it in keeping with Kevin's recommendation in the earlier post. I'm not saying it is cured, but I am narrowing down the variables. Rock Auto lists different cap pressures between the years 1999 and 2001. The underside of the Delco cap on my son's car reads "1999, 2000, 2001". Anyway I plan to see how it goes because I still do not understand why the car has a much more proclivity to overheat now, than it has in years past. How much could age play into it? I don't know. I will verify the mix of coolant next, because it could be off by quite a bit as well.

I'll keep you updated as I go along.. Thanks again for all your discussion.

Sincerely,

Ohio Jim

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Update,

Well the 18# surge tank cap has worked 20 miles back and forth to work for a few days. I'm not convinced I'm out of the woods yet. The temp is dead on the middle of the gauge all the way, to and fro. The surge tank cap looks as though it is leaking steam in small puffs. I will be attempting to drive the car 125 miles Wednesday, so we will see if it comes home on a hook, again. the windows were mighty wet on the inside when I went out to the car this evening... I'll have to check that carpet on the passenger side front, for a heater core leak.. Oh My!

Wish me luck...lol

Ohio Jim

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Kevin how is the copper tubing connected to the spark plug? Threaded?

In the description of pressuring the cylinder how tricky is it to keep it at TDC when pressurized without accidently kicking the cylinder down? Does it pressurize 100% of the time? I suppose it would be prudent NOT to leave a socket/breaker bar attached to the crank bt when pressurizing or pressurized, for safety sake?

The pipe is connected to the spark plug via a tapped connection. The pipe looks like copper but it is an 1/8" pipe from the plumbing section of Menards. I Loctited the connections so they would not come apart when removing the adapter from the engine.

If I recall correctly, the crank will rotate when a cylinder is pressurized - I left the breaker bar in place and wedged it so it wouldn't move. A flywheel lock could also be used but it is more work.

Just saw this, interesting idea to leave and wedge the breaker bar but what if the engine rotates in the other direction? It can can't it?

Thanks for the info on the spark plug adapter, I remember when the guru gave us the idea.


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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Just saw this, interesting idea to leave and wedge the breaker bar but what if the engine rotates in the other direction? It can can't it?

It all depends on what side of TDC the piston is on.


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

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A few things can happen by wedging the breaker bar. The worst is the head of the crank bolt can snap off, it a would a similar situation to over torquing it. Or if the engine turns backwards there is a chance of loosening the crank bolt. That's an easy fix. But I hate broken crank pulley bolts.

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A few things can happen by wedging the breaker bar. The worst is the head of the crank bolt can snap off, it a would a similar situation to over torquing it. Or if the engine turns backwards there is a chance of loosening the crank bolt. That's an easy fix. But I hate broken crank pulley bolts.

The shop air pressurizing the cylinder won't break the crank bolt off nor will it loosen it. That bolt is very tight - something like 50 ft-lbs. plus 120°. You can hold the breaker bar with your hand while the cylinder is pressurized - that is what I did when I checked mine.


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

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