Not quite overheating

[Zed Head]

On 11/18/2022 at 1:20 PM, Zed Head said:

Just remove it and see if the system can cool things down.  The engine should never get up to operating temperature without a thermostat.  If it can't keep things cool then it won't matter what thermostat you have in there.

 

On 11/20/2022 at 8:09 AM, chaseincats said:

I'll give that a shot, thanks!

 

On 11/20/2022 at 9:07 AM, Racer X said:

But as Zed pointed out, the thermostat holds coolant flow back until the system reaches operating temperature.

If the engine is running too hot, it is likely a problem with the radiator, the smaller cooling passages in the cylinder head, or the impellers of the water pump eroded from electrolysis.

Have you done this, to confirm that more flow will actually solve the problem?

[chaseincats]

14 hours ago, Zed Head said:

 

 

Have you done this, to confirm that more flow will actually solve the problem?

I did not.

 

I felt that since the car will have a thermostat regardless, testing one to confirm it works as advertised before putting it in would negate that test especially since I confirmed the original OEM one was broken and the newer aftermarket one is more-or-less defective by design.

Edited December 12, 2022 by chaseincats
clarity added

[jonathanrussell]

I have observed the same thing regarding thermostat hole opening size between original and new Stant etc thermostats.

In my 240z at least, the thermostat brand makes no difference regarding the operating temperature...even in Atlanta heat. My point is, and for my car at least, the operating temp depends primarily on all of the other cooling components working properly.

Edited December 12, 2022 by jonathanrussell

[Zed Head]

The thermostat is actually opening and closing continuously during operation at designed operation temperature.  If it just opened fully and stayed open there would be no temperature control.

[chaseincats]

11 minutes ago, Zed Head said:

The thermostat is actually opening and closing continuously during operation at designed operation temperature.  If it just opened fully and stayed open there would be no temperature control.

Right.  The old OEM thermostat opened 20 degrees later than it should have and even at well over 200 degrees didn't fully open.  The aftermarket one reacted more along the lines of the brand new oem thermostat but it's opening isn't as large and the plunger travel isn't as far since it is physically smaller.

[Zed Head]

The bottom line is - if the cooling system can't cool with no thermostat it will never cool with a thermostat.  You're probably spending your radiator money on thermostats that you don't need.

[chaseincats]

42 minutes ago, Zed Head said:

The bottom line is - if the cooling system can't cool with no thermostat it will never cool with a thermostat.  You're probably spending your radiator money on thermostats that you don't need.

It has a brand new 3-core radiator.  Everything on the cooling system was changed.

[Zed Head]

I was making a general point.  

Where will you go from here?  What does your old Z mechanic suggest?  Maybe you really just have a hot spot by your temperature sender.  How about that?

 

On 5/22/2022 at 11:18 AM, chaseincats said:

My car used to sit rock solid at 170 (has a 170 degree thermostat) but within the past year that's become more variable depending on if I'm sitting idle or driving.  If sitting idle in 95 degree weather, it will go a little past half which I know isn't bad but the fact that it used to sit rock-solid at 170 regardless of weather tells me there's something wrong and even though its not severe it's annoying lol.

I've changed the fan clutch, thermostat, water pump, checked fanbelt tightness, changed coolant, used a flushing chemical, and even got a brand new radiator but while the temperature isn't moving as much, the needle still moves depending on if idling or driving.  There is definitely rust in the system because the PO used tap water and ever since I got it years ago, its been a game of 'how much rust will come out with this flush' (its always less but there nevertheless).

 

[chaseincats]

15 minutes ago, Zed Head said:

I was making a general point.  

Where will you go from here?  What does your old Z mechanic suggest?  Maybe you really just have a hot spot by your temperature sender.  How about that?

 

 

Gotcha.  He suggested changing back to an OEM style thermostat and if that doesn't work to knock out the back-right freeze plug (the one above the starter) and flush the engine out again through the thermostat housing.  He said IF there's rust in the block, it usually sticks around near that freeze plug.

Edited December 12, 2022 by chaseincats

[Zed Head]

Have you ever had the head off?

[chaseincats]

51 minutes ago, Zed Head said:

Have you ever had the head off?

Not since I've owned it 7 years ago.  I did do a leakdown test to make sure no combustion gasses were entering the coolant through the head gasket and the head gasket came back as solid.  There isn't any chocolate milk under the coolant/oil caps.

[Zed Head]

I was thinking of blocked passages in the head gasket.

I'd probably back flush the system myself, if I was reasonably sure that everything else was right.  Push any blockages back toward the water pump and out the inlet.  Disconnect the radiator, hook up a hose to the thermostat housing (outlet port) and see what comes out.