Leaking coolant

[CANADIANCADDY]

Hi there

A few weeks ago while driving our 98 STS the low coolant warning came on. To my surprise it took almost a gallon of coolant/water mix to fill it up following which I had my mechanic check for leaks only to hear that he couldn't find any. This surprised me as I had seen coolant on the ground and on the inside of the driver's side front wheel and tire when I first investigated the problem in my driveway.

Over the last few weeks we have lost very little coolant and merely replaced it as needed while trying to find the source of the leak.

Today however and against my instructions (can you believe it?) my wife decides to do a 30 mile run out of town on the highway only to call me in a panic to say that the car seemed to be out of coolant.

As always I rushed to her aid and after putting about a gallon of coolant in the car I went straight to my mechanic who after a couple of hours of investigating called to say that while he couldn't see any leaks he did spot a damp area around the intake plenum/gasket?

He believes that this may be leaking slowly until it reaches the point where the car overheats and we lose further coolant.

Does this sound plausible to you?

Has anyone faced this problem?

Is it a big deal to fix?

Many thanks for any insight you can provide on this.

Paul

[JimD]

There is no coolant flow through the intake manifold.

What you might have seen on the LF side "could be" from the coolant crossover casting on that end of the engine.

If you have trouble pin-pointing the source, you could try maintaining 15 psi on the system overnight and see what there is to see in the morning.

Or, throw 2 tubes of Bar's Leaks Golden Seal powder in one of the hoses.

[BodybyFisher]

Its possible that your water pump is leaking under pressure, take a close look at it

[KenD]

I had the same problem and replaced the water pump, added 3 GM tabs and all is good. Water pump replacement was easy enough once I started. A little messy with some coolant spilling out of the thermostat but easy enough none the less.

I got the water pump tool from Bruce and it worked like a charm. Total of about 1 hour RR

[BostonETC97]

Identical problem in my '97 two weeks ago. Turned out to be the water pump loosing coolant under higher RPMs. When i revved the engine up to about 3500+, a real steady stream of coolant started pouring out of the water pump. Under 3500, there was not a trace of a leak to be found. The coolant was spraying straight down to the ground, but would drip off the left side of the subframe.

With a flashlight handy, have someone rev up the motor (or move the throttle linkage under the hood), and look for a leak that appears when the system is under pressure. The pump is easy to change with the right tools, and not a big deal at all.

Hope that helps!

-Scott

[Ranger]

There is no coolant in the intake manifold, but there is coolant in the TB.

[growe3]

Sometimes hoses seem fine, but will leak when hot and under pressure.

1. Use a nut driver (or screwdriver) to tighten all of the radiator hose clamps, on the driver’s side area.

2. From the driver’s side, lean over the fender and look down next to throttle body, just to the right are two green silicone heater hoses. Use a long screwdriver to tighten the four clamps. If either of these green hoses ever need to be replaced, they must be OEM parts; not regular heater hose.

See attached image file, you can see one of the two green silicone hoses

Is any steam coming out of the exhaust pipes? You can smell the coolant if it is coming out there. If so that is a bad sign, usually it means that one, or both of the head gaskets have failed.

-George

[adallak]

Identical problem in my '97 two weeks ago. Turned out to be the water pump loosing coolant under higher RPMs. When i revved the engine up to about 3500+, a real steady stream of coolant started pouring out of the water pump. Under 3500, there was not a trace of a leak to be found. The coolant was spraying straight down to the ground, but would drip off the left side of the subframe.

With a flashlight handy, have someone rev up the motor (or move the throttle linkage under the hood), and look for a leak that appears when the system is under pressure. The pump is easy to change with the right tools, and not a big deal at all.

Hope that helps!

-Scott

That's exactly what I wanted to suggest - revving the engine in Park to some 3000-4000 RPM. It was the only way to discover my heater valve (the plastic "T") was leaking. Same applies to other weak links.

[BodybyFisher]

The NS does not have a plastic T, but it has heater pipes at the rear of the engine, three heater hoses, two green hoses, a by-pass hose and the water pump cover where leaks can occur, not to mention the water pump seal. Also, the radiator end tanks can leak.

[JimD]

.... I had seen coolant on the ground and on the inside of the driver's side front wheel and tire when I first investigated the problem in my driveway.

....

Paul

Another possible leak source on the left side would be the coolant reservoir and the two rubber hoses that plumb the reservoir to the rest of the system. I have heard of stress fractures in the hose fittings as well as cracks in the reservoir itself. Not that bad a job to remove and carefully inspect the reservoir.

For future readers: Paul's car is a '98 Seville and several cooling system components were re-located beginning with that year due to the new/diffferent chassis layout. Also, the rubber hoses that connect to the heater core - water pump inlet - reservoir on my '98 are common old black.

[CANADIANCADDY]

Hi again

It appears as if the leak is a small one located at the black plastic type gasket near the intake manifold. I think over a period of time I slowly lose enough coolant to make the sytem overheat and perhaps actually force a large quantity of remaining coolant out the cap blow.

Does anyone know if this could be the case?

Thanks Paul

.... I had seen coolant on the ground and on the inside of the driver's side front wheel and tire when I first investigated the problem in my driveway.

....

Paul

Another possible leak source on the left side would be the coolant reservoir and the two rubber hoses that plumb the reservoir to the rest of the system. I have heard of stress fractures in the hose fittings as well as cracks in the reservoir itself. Not that bad a job to remove and carefully inspect the reservoir.

For future readers: Paul's car is a '98 Seville and several cooling system components were re-located beginning with that year due to the new/diffferent chassis layout. Also, the rubber hoses that connect to the heater core - water pump inlet - reservoir on my '98 are common old black.

[JimD]

A picture; we need a picture.

[CANADIANCADDY]

A picture; we need a picture.

Picture of engine: http://i12.tinypic.com/47i1rw6.jpg

Close-up of gasket: http://i12.tinypic.com/4bybzu0.jpg

(Wooden skewer points to leak)

At the time, it seemed to be coming out of here. Since then, our mechanic (and then myself) have put in some Stop Leak, and replaced the cap with a newer, 18psi rated one. After doing this, it seems to have stopped leaking from this spot and is now intermittently leaking out somewhere near the lower part of the engine, on the drivers' side.

Also noticed recently is that the engine has a tendency to get hot (the gage will move to 3/4ths), and the air coming into the car, even with thermostat set at 32º, will lose its heat and go cold. This has happened on several occassions, both while driving downtown and driving on the highway. It is intermittent, and will only last a little while; the air will eventually start to get hot again and the H/C gage will creep back down to the middle.

Any additional thoughts? Possibly a sticky thermostat causing all of this?

[JimD]

A picture; we need a picture.

Picture of engine: http://i12.tinypic.com/47i1rw6.jpg

Close-up of gasket: http://i12.tinypic.com/4bybzu0.jpg

(Wooden skewer points to leak)

At the time, it seemed to be coming out of here. Since then, our mechanic (and then myself) have put in some Stop Leak, and replaced the cap with a newer, 18psi rated one. After doing this, it seems to have stopped leaking from this spot and is now intermittently leaking out somewhere near the lower part of the engine, on the drivers' side.

Also noticed recently is that the engine has a tendency to get hot (the gage will move to 3/4ths), and the air coming into the car, even with thermostat set at 32º, will lose its heat and go cold. This has happened on several occassions, both while driving downtown and driving on the highway. It is intermittent, and will only last a little while; the air will eventually start to get hot again and the H/C gage will creep back down to the middle.

Any additional thoughts? Possibly a sticky thermostat causing all of this?

Your pictures are of the coolant crossover attach point to the rear (firewall) head. But it sounds like you got that stopped with some Bar's Leaks. We hope you used the recommended product and not a generic liquid "stop leak".

Your HVAC blowing cool or cold air means there is air in the system and that means there is a large enough leak to drop the coolant in the reservoir and the cooling system is pulling in air instead of liquid.

I would pressurize the cooling system and get under and around with a bright light and locate the leak. You will have to search for an adapter to fit a pump to the threaded fitting on the reservoir. Maintain at least 14 psi on the pressure pump while the engine cools.

It is also important to check the purge line. That is the small diameter rubber hose that attaches near the top of the reservoir. That line should flow a stream of coolant with the engine at idle.

[JimD]

Paul:

I'll answer your email Q here to keep all the responses available for the possible benefit of future readers.

A failing or failed thermostat will not introduce air into the system but it can cause temperature fluctuations.

[CANADIANCADDY]

Well here's an update on the problem. As I had to go out of town and my local garage couldn't seem to pinpoint the source of the coolant leak or overheating I unfortunately had to drop it off at the Caddy Dealer. After having it for a couple of hours they called to say there was a crack in the side of the rad which surprisingly my mechanics never identified. I must admit that I could never trace the leak to the rad either.

I told them to go ahead and replace it with an aftermarket version along with a OEM thermostat and a coolant system flush.

Car won't be ready until tomorrow and I just know I am going to shoot myself if the approach I have taken still doesn't solve the problem.

This is a very major Caddy dealership I am using here in Toronto so I am keeping my fingers crossed that their guys know what they are doing and wouldn't screw me by replacing something not required but you just never know do you?

[BodybyFisher]

The side tanks will leak when they are under high pressure. They get fine cracks in them that only open up under 16+ PSI and when the coolant excapes it immediately vaporizes... That is why its hard to find. You might have been able to find it, if you pressurized the system cold to 17 PSI it would not vaporize with the system cold and you might see a drip.

If they do not put in the cooling supplement do so (NOT IN THE TANK), crush them and put them in the upper hose when the system is cool. It has been said to put them in the lower hose but its easier to get to the upper hose and you loose less coolant doing the deed.. Mike

[CANADIANCADDY]

Not good news. After a new rad, themostat, coolant system flush and fill up I discovered today that I have lost over a gallon of coolant since my 1100.00 repair bill at City Buick Cadillac in Toronto 11 days ago.

I just can't seem to pinpoint the leak unless it is the gasket of which I posted a picture a few weeks ago.

I guess I will have to return to the dealer tomorrow and hear that I must have "multiple" leaks.

I have that feeling that perhaps I have been hosed!

[CANADIANCADDY]

The news keeps getting worse.

The dealer just called to say that my head gasket is shot.

I wished they had of told me this 10 days ago before they replaced the rad, themostat along with a flush and fill at a cost of $1100.00

They are suggesting a new engine at between 8000.00 and 8500.00!

Do I have any options other than this or taking it to the wreckers?

[BodybyFisher]

The news keeps getting worse.

The dealer just called to say that my head gasket is shot.

I wished they had of told me this 10 days ago before they replaced the rad, themostat along with a flush and fill at a cost of $1100.00

They are suggesting a new engine at between 8000.00 and 8500.00!

Do I have any options other than this or taking it to the wreckers?

Yes, they should be able to time-sert the engine for between $2200 and $3000...

[CANADIANCADDY]

Is the diagnosis of a blown head gasket a fairly easy one for a Cadillac dealer to arrive at?

Is it possible they could be mistaking something else for this?

Why would they have not checked for this problem before replacing my rad, thermostat and doing a flush and fill?

I told them about all of the conditions I was experiencing and the fact that we (myself and two mechanic friends) could find no leak although I do believe there was a very very small one on the other gasket I posted on this board.

[Ranger]

Is the diagnosis of a blown head gasket a fairly easy one for a Cadillac dealer to arrive at?

Is it possible they could be mistaking something else for this?

Why would they have not checked for this problem before replacing my rad, thermostat and doing a flush and fill?

I told them about all of the conditions I was experiencing and the fact that we (myself and two mechanic friends) could find no leak although I do believe there was a very very small one on the other gasket I posted on this board.

Sure it is easy to diagnose, for a Caddy dealer or anyone else for that matter. If they did not do the proper diagnosis it could easily be misdiagnosed. You would not be the first. Did you and your mechanic friends do a cylinder pressure test? If so, and it turned up negative, then I would be leary and ask them exactly how they diagnosed a bad head gasket.