Not quite overheating

[chaseincats]

36 minutes ago, Zed Head said:

It's not an "overflow" bottle.  It's a reservoir.

Interesting, got it.

Regarding the combustion gas in the coolant, I'd guess I would see small bubbles in the coolant with the cap off if that were the case though, right?  I ran it with the cap off when I changed the coolant to make sure everything was good and didn't see any with the car at 170.  I can go grab the test kit and test anyway if you guys think its still possible without visible bubbles.

Edited May 28, 2022 by chaseincats

[siteunseen]

20 hours ago, w3wilkes said:

With Dallas being fairly close to sea level the boiling point of water is right about 212*F. Based on that you've got about 15*F to play with if you ran straight water. Then mix that with antifreeze which has a boiling point of around 387*F a 50/50 mixture would have a boiling point around 223*F so you would have almost 30*F to play with before you boil. You will have a little more room due to the cooling system being pressurized which will raise the boiling point temp even more. One other little thing is that water typically is the best at heat transfer where the 50/50 water / antifreeze may not be quite as good at transferring heat from the engine. This is kind of just off the top of my head. I'd bet @Captain Obvious or @siteunseen would be able to provide more and probably better enlightenment!

My thought is you should be okay at 195*F and I'm sure as soon as you start moving it will come down.

Mine stays at 173F idiling in it's garage. Good flow at the radiator hole on top when I rev it up. No wind flow other than the stock fan with a full shroud off a ZX pulling air through the radiator.

Water boils at 225F way up here in North Alabama where I live and I run 75>25 coolant and distilled water I collect from a dehumidifier running downstairs where the Zs are.

195F doesn't seem that high to me but I've always heard 200 to 225F is not good. Maybe do an IR temp check at the bottom radiator hose where it connects to the radiator and then get a reading at the thermostat housing to what kind of job the radiator's doing. Do the same where the in and out are on the block. That way you'd know if it's the radiator or the block I would think.

[Zed Head]

CO's comment about the reservoir is the most important one to focus on at this point.  Apparently, you've been running with a low coolant level for quite a while.  That's not good.

Get the system back to the way it is designed to be and see what happens.  If you lose coolant, there's a leak, as the FSM says.  If you determine that you have a leak there are ways to find it.  You can also verify a leak by pressurizing the coolant system.

And, don't overlook that the coolant system is designed to use a certain type of radiator cap.  The cap releases pressure but also holds vacuum.  So that the coolant can pass between the radiator and the reservoir as it is designed to do.

As far as looking for bubbles, the chemical test was developed and is widespread because the bubble method is not reliable.

[chaseincats]

Update on this.  I noticed a few weeks ago that the temp gauge briefly rises when I really hit the pedal and will fall when I drop the idle.  That lead me to believe theres combustion gas sneaking into the coolant.

Following the directions, I siphoned out a few inches of coolant from the radiator and after about 20 seconds of pumping, the squeeze pump stopped expanding because I was probably pulling coolant into the tester at that point.  Because of this, I was unable to do a full 2 minute squeeze test.  My question is, can I squeeze the pump until its hard to squeeze, pop it out of the radiator to drop the coolant level back down (now that its no longer under vacuum from the bottle) so I can keep squeezing (as long as I dont squeeze the bulb when I pop it out) or will that contaminate the test?

EDIT: I grabbed my transfer pump and sucked enough coolant out of the radiator to fill my overflow bottle (it was about 1/8 full).  That gave me more air to pump out of the rad and the color didn't change.  My only guess at this point is the leak in the head/head gasket (if that's the issue) is so small that the only time it gets enough gas to heat the car up is when theres more pressure in the cylinders due to higher rpm.

I think the plan will be to just drive it until it's bad enough that it heats up at idle and try the test again.

Edited October 15, 2022 by chaseincats

[chaseincats]

Update on this.

I noticed the car is now only heating up after getting to operating temperature and then driving slowly/idling.  Once the car is driving, the temperature drops like a stone which kills my theory about combustion gas in the coolant.  They car will puff some white (not blue) smoke when changing gear under WOT so I'm guessing that means the gasket is somewhat compromised in the coolant passages anyway.

The car has a brand new Aisin fan clutch which had the same warming-up issue that developed with the old fan clutch which was in good condition anyway.  I checked the fan belt's tension and it was good as-is too.

Any other ideas?

[Mark Maras]

 When you say "Once the car is driving, the temperature drops like a stone", (assuming it's at operating temp) does it go down to operating temperature or lower?

[Zed Head]

What does it do if you hold the engine at higher RPM than idling?  Maybe your water pump is bad.

And is your fan shroud intact?

[chaseincats]

14 minutes ago, Zed Head said:

What does it do if you hold the engine at higher RPM than idling?  Maybe your water pump is bad.

And is your fan shroud intact?

When this whole thing started I changed the fan clutch, radiator (kept the fan shroud), water pump, thermostat, and used radiator flush so it shouldn't be any of those components...

[Zed Head]

1 hour ago, chaseincats said:

the car is now only heating up after getting to operating temperature and then driving slowly/idling.  Once the car is driving, the temperature drops like a stone

This is usually air flow but could also be coolant flow.  Is your heater core intact or do you have it bypassed?

[chaseincats]

7 minutes ago, Zed Head said:

This is usually air flow but could also be coolant flow.  Is your heater core intact or do you have it bypassed?

Heater is good.  I do have an aftermarket thermostat installed not OEM Nissan if that matters.  The original thermostat I had in there was OEM but the overheating issue also happened with that in there.

Next time I drive the car and it heats up I'll raise the idle and see what happens but either way that should test airflow and coolant flow since it would be spinning the pump and fan faster, right?

Edited October 24, 2022 by chaseincats

[chaseincats]

42 minutes ago, Mark Maras said:

 When you say "Once the car is driving, the temperature drops like a stone", (assuming it's at operating temp) does it go down to operating temperature or lower?

drops back to operating temp

[Mark Maras]

29 minutes ago, chaseincats said:

 

Next time I drive the car and it heats up I'll raise the idle and see what happens but either way that should test airflow and coolant flow since it would be spinning the pump and fan faster, right?

 Almost right. Along with spinning the pump and fan faster you're also running the engine faster which means more heat is created in any given length of time than it would at idle. Out of curiosity are you using a fan shroud?