Temp Gauge goes to Overheat while stuck in traffic

[Cadillac Jim]

We have two threads going on this topic!

-Chris- (1999 STS): If you were driving over 125 mph (200 kph) then your car has the governor removed. Either it was sold with Z-rated tires or your dealer took off the governor.

If you drove over 120 mph (195 kph) at all and did not have overheating, then your head gaskets are fine.

The only thing that I can think of off the top of my head that would explain the temperature going low when you slowed down, but then going up a little as you went up a hill, is the thermostat sticking. I would also check the bypass for clogging, since that can mimic a stuck thermostat.

Kens96 (1996 ETC): I believe that this is your kit:

http://www.napaonline.com/Search/Detail.aspx?R=BK_7001006_0254106784

Since the fluid is dark blue and your reading was a little greenish when the kit said yellow was a pass, I would say that your test was a *PASS*. I see that BodyByFisher beat me to a post, and he has a good approach to the next thing, cleaning the bypass.

[kens96]

Yes Jim, that is the kit that I have. The liquid did turn green. Here is how I checked the bypass. With the engine off and reservoir cap removed, I pulled the hose off the hole bolt and coolant came flowing out with a good strong stream. Reinstalled the hose. Removed the 3/8 hose from the reservoir tank and blew through the pipe that goes under the beauty cover until I could hear it bubbling in the reservoir tank. Then I pulled a vacuum with a Mighty Vac on the same line until anti freeze started flowing. Was there other lines I should check? As a follow-up I have been out all morning hopping from store to store, sitting at traffic lights, and some minor highway speed driving with the AC on and the outside temperature at 75. The temp gauge has not moved off center and there is no steam coming from the exhaust. Jim I think you are correct about the steam we saw yesterday with the temp and humidity what it was. The high temps could have been the result of the system needing some cycles to complete the purge. When I started the car this morning I did not smell any coolant and we didn't have any steam from the exhaust. At this point my plan is to monitor for coolant loss weekly and watch the temp gauge. I redid the test and it is a yellow color more then green so I do have combustion gases in the coolant system.

[Chris_Austria]

My termostat is almost new, so I will check the bypass and the hose that leads into the ground of the surge tank. (this one is there for ventilation?)

Maybe the export version of the Seville has no limiter? My winter tires are rated 210kph (H) and the summer tires 240kph and more (the old ones W, the new ones Y).

When driving such fast the temp gauge is exactly in middle position. When the summer tires are on, I will try how fast it can go

[Cadillac Jim]

-Chris-: The bypass is there for similar reasons it is there on any car: to provide a flow of water through the system when the thermostat is closed. In the Northstar, it also serves to ensure circulation in the surge tank, and provides a return path to purge air from the system.

Whether the STS/ETC has the governor or not depends on the tires bought on the car when it was new. It is illegal to drive faster than your tires are rated on the Autobahn, so they have the governor unless your tires are rated for 150 mph (242 kph). Apparently your original tires were W rated.

kens96: I thought that you said that yellow meant your radiator water was OK. The usual way to check the bypass is simply to pull it off the surge tank and start the engine for a few seconds and see if it has a good flow. Point it where coolant won't hurt anything -- not on the paint, please. It's beginning to sound to me like there is nothing wrong with your car anymore. It may have had a partially clogged byapss but it sounds normal now.

[kens96]

Jim - Sorry I was not clear.The test is positive if the Blue fluid turns Yellow, there are combustion gases in the coolant. Looks like we are on borrowed time.

[Ranger]

The purge line is how the air gets out of a Northstar system. It's also used in keeping the surge tank water close in temperature to the rest of the coolant temperature. It's a 3/8" rubber hose that goes from the water pump to the bottom of the surge tank.

It's at the top of the tank Jim.

[Cadillac Jim]

Uh, top of the surge tank. Thanks, Ranger.

That's what I get for depending on the FSM. I actually have essentially no problems with my Cadillac.

[KHE]

The block test kits seem to be a little on the subjective side. They are also pricey - last time I checked they were around $50.00. I would suggest making a soark plug air adapter, bring each cylinder to top dead center on the compression stroke (use a wood dowel to check the position of the piston), lock the flywheel and pressurize the cylinder with 120 psi from an air compressor while observing the coolant in the surge tank. If you see bubbles, the head gasket is shot. Repeat for the other 7 cylinders.

Attached is a picture of the adapter I made a few years ago from an old spark plug and less than $5.00 in fittings.

[kens96]

Drove it to work today and the gauge rose to the first mark to the right of center just as I pulled into the parking lot. About a 30 mile trip mostly highway. Parking the car when I get it home tonight. Looks like its time to shop!

[BodybyFisher]

Drove it to work today and the gauge rose to the first mark to the right of center just as I pulled into the parking lot. About a 30 mile trip mostly highway. Parking the car when I get it home tonight. Looks like its time to shop!

Sorry to hear this Ken

[Chris_Austria]

When the gauge rises to the first mark to the right... will it go further or will it go back to normal if you raise the rpm? I had this symptom (never got over normal while I was driving!) and now it has disappeared without doing anything. Head gasket is fine, had it tested (because I still have guarantee on it). The problem on my car has (had) to be something else.

[CarlaValentine]

If it were the head gasket, raising the RPM's would make the temp climb. Putting any more strain on the engine would raise the temp.

[Texas Jim]

Drove it to work today and the gauge rose to the first mark to the right of center just as I pulled into the parking lot. About a 30 mile trip mostly highway. Parking the car when I get it home tonight. Looks like its time to shop!

Ken,

The symptoms you are having just do not fit the normal "HEAD GASKET" symptoms.

Just my opinion...but I think you have another issue, other than head gaskets.

I just wish I knew what it was.

[Cadillac Jim]

When the gauge rises to the first mark to the right... will it go further or will it go back to normal if you raise the rpm? I had this symptom (never got over normal while I was driving!) and now it has disappeared without doing anything. Head gasket is fine, had it tested (because I still have guarantee on it). The problem on my car has (had) to be something else.

It sounds like you were low on coolant or had a clogged bypass, but it's all better now.

[kens96]

Wish I could say its not the HG but read the attached link. This is exactly what I have happening and it makes sense. AS a follow-up when I drove the car home it was okay until the last 1/2 mile then sitting at a light the guage started climbing past the first mark to the right and the idle started to get a little rough intil I started moving then all was normal.

http://www.cadillacforums.com/forums/north...ned-yellow.html

[Chris_Austria]

But when you're driving the temp goes back to normal? With a bad head gasket the temp should increase while you are driving... maybe it's a clogged bypass.

A repair shop should have a test-sensor for exhaust gases. Get the car to operating temp, let it cool down some minutes (10-15) and then open the cap on the surge tank slowly with the sensor aside... this should finally prove if you have exhaust gases in your coolant.

[Ranger]

In the early stages of a HG failure, raising the RPM will circulate the coolant and bring down the temperature. As the breach gets worse, it will then start putting more exhaust gases into the system thus making the overheating worse.

[Cadillac Jim]

The nose knows. Beginning at the point where the only symptom is coolant loss without a visible leak, you can smell the coolant in the exhaust right after you start it in the morning. That early in the problem, a good radiator shop can find it by testing the coolant or possibly with a pressure test. A compression test, putting each cylinder at TDC and pressurizing it through the spark plug hole with shop air and watching the surge tank for bubbles, is the "big hammer" that will find any head gasket leak. But, the nose test is easy, simple, definitive in the sense that if you smell coolant there then you do have the problem, and free.

[BodybyFisher]

Ken, you probably will be feeling a misfire in the morning till the engine is warmed up. That is what I have seen with others here and what I get. I am not sure why that happens, if coolant is leaking into the cylinder, why doesnt it leak enough to hydrolock the piston?

Anyone have any ideas as to what causes the temporary misfire in the morning?

[Chris_Austria]

When my head gasket was bad, i couldn't drive 30 miles on the highway without having a high operation temp and after only a few miles 1 quart of coolant was gone without an external leak. If you don't have these symptoms I really would make a check like Jims_97_ETC suggests.

The time when I had the problem with the temp gauge getting to the first mark after normal while I was stuck in traffic the coolant level was always good (at cold mark after cooling down). I also thought that maybe there is a relation to the engine-oil level, the time I had these symptoms the oil level was pretty low as I discovered later (5,5 quarts instead of more than 7) This time the head gaskets were tested by a repair shop and they were good!

[CarlaValentine]

Ken, you probably will be feeling a misfire in the morning till the engine is warmed up. That is what I have seen with others here and what I get. I am not sure why that happens, if coolant is leaking into the cylinder, why doesnt it leak enough to hydrolock the piston?

Anyone have any ideas as to what causes the temporary misfire in the morning?

Just a theory/shot in the dark here...I'm not sure really how to put the image in my head into words here but could it possibly be because coolant is typically non-combustible, and it being in the cylinder doesn't allow the spark plug to fire correctly until the engine warms up a bit, causing a misfire?

As for the hydrolock thing, to be honest I'm not even familiar with the term, so I have no ideas there.

[Ranger]

Ken, you probably will be feeling a misfire in the morning till the engine is warmed up. That is what I have seen with others here and what I get. I am not sure why that happens, if coolant is leaking into the cylinder, why doesnt it leak enough to hydrolock the piston?

Anyone have any ideas as to what causes the temporary misfire in the morning?

Mike, when you shut the car down the cooling system is under pressure and a small amount of coolant gets pushed into the cylinder. Once the pressure decreases, the leak stops. When started in the morning, the plug is fouled by the noncombustible coolant as Carla mentioned until it gets expelled and the plug can fire again. If the gasket breach was so bad as to allow coolant to "leak" into the cylinder bad enough to hydrolock it, the engine would probably be unusable long before you got to this point.

Carla, hydrolocking is when a cylinder ingests a liquid (non compressible), either water by driving through very deep water or coolant or gas by whatever means to the point that it will fill the cylinder to some point during the compression stroke. Being noncompressible, the piston runs up against a brick wall so to speak and comes to an abrupt stop. Usually bending a rod or throwing it through the side of the block. It's almost always fatal.

[BodybyFisher]

Here is what happens when an engine is hydrolocked, because a liquid gets into the combustion chamber and on the compression stroke, it has no place to go, so the ROD ends up out the side of the engine

[CarlaValentine]

Ewww...that doesn't look pleasant in the least little bit.

This must be why mudding trucks use a "snorkel" on the air intake...

Note to self: Stay the heck away from really deep puddles! My street is like a river when it rains.

[BodybyFisher]

Ewww...that doesn't look pleasant in the least little bit.

This must be why mudding trucks use a "snorkel" on the air intake...

Note to self: Stay the heck away from really deep puddles! My street is like a river when it rains.

Believe it or not, this was caused by a GM tech, he sprayed throttle body cleaner into the TB, it pooled, and as soon as he accelerated the engine, the liquid was sucked into the cylinder and BAM... GM replaced the engine

This is why I am reluctant to spray anything into the intake