Not quite overheating

[Zed Head]

Cylinder pressures at engine temperature are much greater than the leak-down test.  And coolant gets sucked in due to engine vacuum.

For a problem like yours, where you're on the edge, it would have been best to start with a properly filled and maintained system.  You started with an empty reservoir, but didn't really say if it was ever full.  Most of us never see any change at all in out coolant reservoirs.  I have often wondered on my various cars if it was even working, the change was so indiscernible.  If a change did happen it would have been concerning.  Empty would be panic.

Edited December 17, 2022 by Zed Head
- e spell check is bad

[chaseincats]

20 minutes ago, Zed Head said:

Cylinder pressures at engine temperature are much greater than the leak-down test.  And coolant gets sucked in due to engine vacuum.

For a problem like yours, where you're on the edge, it would have been best to start with a properly filled and maintained system.  You started with an empty reservoir, but didn't really say if it was ever full.  Most of us never see any change at all in out coolant reservoirs.  I have often wondered on my various cars if it was even working, the change was so indiscernible.  If a change did happen it would have been concerning.  Empty would be panic.

As long as I've owned the car it was never full because the old radiator had a pinhole leak at the top and didn't hold pressure but always kept the car at 170.  The new radiator is filled to the brim but not the reservoir tank.

If the car's problem was the head gasket though, wouldn't it run warm all the time regardless of airflow through the radiator?

[Zed Head]

Not sure why you can't just, as my father used to say, "get with the program".  You're refusing to follow basic maintenance guidelines.  The Z engines are fun learning tools though.  You can do all kinds of crazy things to them and they just keep running.

[Racer X]

10 hours ago, chaseincats said:

With the old smaller thermostat the car would get up to 180+ at idling but when starting from a stop (at a traffic light for example), the car would drop back down to 170 after a few minutes of air flowing through the radiator at road speeds.  With the new larger opening thermostat, it will get up to 180+ at idle but when starting from a stop with this new thermostat, the car drops to 170 within a matter of seconds - the car is cooled way faster with the larger OEM thermostat.

So the temperature range is 170 to 180 ish, correct?
 

When it drops back down to 170, is that as low as it goes?

 

 I think it is operating just fine. Wouldn’t start to worry unless it gets to 190 and doesn’t want to cool down. 

 

[Racer X]

12 hours ago, Racer X said:

So the temperature range is 170 to 180 ish, correct?
 

When it drops back down to 170, is that as low as it goes?

 

 I think it is operating just fine. Wouldn’t start to worry unless it gets to 190 and doesn’t want to cool down. 

 

Further to this, water boils at 212 degrees F at sea level. 
 

A 50/50 mix of water and ethylene glycol boils at around 223 degrees F.

Pressurizing the cooling system raises the boiling point further, to around 226 degrees F, depending on the pressure rating of the cap, the higher the pressure, the higher the boiling point.

So again, unless your cooling system temperature gets at or over 190 degrees F and doesn’t come down, there isn’t anything of concern.

 

 

Edited December 18, 2022 by Racer X

[chaseincats]

13 hours ago, Racer X said:

So the temperature range is 170 to 180 ish, correct?
 

When it drops back down to 170, is that as low as it goes?

 

 I think it is operating just fine. Wouldn’t start to worry unless it gets to 190 and doesn’t want to cool down. 

 

It might go a bit below 170.  Even though 185 to 190 isn’t a huge issue (arguably an issue at all), the fact that it used to get to 170 and sit there regardless of if I’m idling or driving freeway speed means something is not working as it was/should, you know?

[chaseincats]

1 hour ago, Racer X said:

Further to this, water boils at 212 degrees F at sea level. 
 

A 50/50 mix of water and ethylene glycol boils at around 223 degrees F.

Pressurizing the cooling system raises the boiling point further, to around 226 degrees F, depending on the pressure rating of the cap, the higher the pressure, the higher the boiling point.

So again, unless your cooling system temperature gets at or over 190 degrees F and doesn’t come down, there isn’t anything of concern.

 

 

It’s not a boiling issue (at least not yet), the issue is that it isn’t behaving like it was last year when this issue started which tells me something is wrong and will eventually get worse.

[Zed Head]

Take it out and run it and see if temperature keeps climbing or if it just rises and levels out.  Fill up the reservoir first so you can see if the level changes.

Here's a question though - how can you be so precise on the temperature?

[Racer X]

2 hours ago, chaseincats said:

It might go a bit below 170.  Even though 185 to 190 isn’t a huge issue (arguably an issue at all), the fact that it used to get to 170 and sit there regardless of if I’m idling or driving freeway speed means something is not working as it was/should, you know?

At 170 the engine is running cool, a normal range would be 190 to 220. You would likely see an average of 185 to 195 with a cooling system in good operating condition.

[Racer X]

13 minutes ago, Zed Head said:

 

Here's a question though - how can you be so precise on the temperature?

You can’t, really. The actual reading can be interpolated though. The gauge range is 130 degrees.  So the center would be 65 degrees higher than 120, at 185.

At about three quarters of the way it would be approximately 217 degrees.

If it were my Z I would expect to see the needle about 5/8 of the way between 120 and 250, around 201 degrees.

 

And the oil pressure gauge, do the same. Straight up is 45 psi. If the engine is trining 4,000 rpm, I want to see the needle straight up, maybe just a bit more towards 90.

 

Edited December 18, 2022 by Racer X

[Zed Head]

4 minutes ago, Racer X said:

You can’t, really.

This was my point.  The whole thread revolves around guesstimating.  Always fun to discuss cooling systems though.

[Zed Head]

I have a Ford truck now and they completely changed the way the cooling system works.  The reservoir is directly open to the bottom radiator hose.  The pressure cap is on the reservoir, it's 16 psi on mine.  Any bubbles that pass through the bottom hose rise up in to the reservoir.  It's also called the degas bottle.  There's a small hose on the top of the radiator that lets the fluid level in the radiator equalize to the level in the reservoir.  When you see the fluid in the reservoir you're seeing the same fluid that is flowing through the system.   No guessing necessary about level or fluid quality.  It's pretty nice.

Edited December 18, 2022 by Zed Head
+ s