Proper Coolant temperature?

[blue_myriddn]

I believe my engine has been running a bit hot now in then with some spillover from the Coolant tank and now that I have this nifty OBDII reader that displays coolant temperature, I am wondering what the "proper" temperature is for Honda coolant to be running at.

In addition to real time displays (as below), I can also data log it during longer trips to get better readings. On a related note, does anyone know how accurate these OBDII readers are for things like coolant temperature?

 

[Larry Bastanza]

According to Service Manual:

169 F - Thermostat starts to open
194 F - Thermostat fully open

Typical average temp is about 180F

HTH,
LarryB

 

[blue_myriddn]

much appreciated - thanks!

 

[ftuhy]

Its a digital interface, so the OBDII reader simply reports what the ECU tells it. Therefore, the accuracy primarily depends on how accurately the NSX ECU reads and reports the coolant temperature. Sorry, but I don't know the answer to that.

My concern is that your NSX has been running hot and spilling over. Mine has never done that. When was the cooling system last flushed and coolant changed? Was any "crud" discharged at that time? The OEM thermostat usually fails open, with a rubber ring "mushrooming" off of the thermostat moving plate. That failure mode wedges the thermostat open and causes long warm-up times. I suppose if that rubber ring comes fully off (haven't heard of one doing that), it might be possible to cause a blockage.

 

[Honcho]

Burping coolant usually is a sign of air in your system, not overheating. I went through this nightmare during NSXPO at the track. In my case, several coolant hose clamps were broken and the ultimate culprit was a leaky bleeder cap on the heater pipe. You should pressure check your system, but this is not a guarantee- my car held pressure at idle, but was leaking air under load. I would check all your main coolant hose clamps and all bleeders.

As larry said, normal operating temp is about 180. The "normal" tick on your temp gauge is 185 F.

 

[bngl3rt]

You should pressure check your system, but this is not a guarantee- my car held pressure at idle, but was leaking air under load. I would check all your main coolant hose clamps and all bleeders.

Oog... way to make me paranoid. I thought after new MLS head gaskets, new head studs, and a Koyo radiator I was good to go...

- - - Updated - - -

My HG was blown by a misplaced hose clamp. Thanks Hilltop Auto!

 

[warrenw]

If a coolant flush is required or done, it isn't a big deal if done right. There are many posts on this site that explain how to do it and how to bleed the system to ensure no air is in the system when done. The service manual is very good at explaining it as well.
I completely drained my system (removed hoses), flushed with water, drained again, and replaced coolant with Honda Blue. I ensured the nose of the car was lower than the rear, followed the manual bleed process, and after two days on the track the temperature gauge never moved from normal. Getting the air out is the trickiest part, but not difficult. Hot days, cool days, the car warms up in the same amount of time, so I am confident the thermostat is working correctly.

 

[blue_myriddn]

Great thread, I appreciate everyone who has chimed in! Nothing like learning a few new tricks and getting some good advice.

The coolant spilling over is exactly what I was experiencing (photo below). I thought it was simply a bad seal with the cap as it is an aftermarket coolant tank, but all the gaskets were in good shape and it appeared to be connected properly. I had the car at Daisy auto, and I think he did a full coolant flush but Ben has been pretty busy so I haven't gotten really detailed run down on what he did. There are 3 bottles of Honda coolant, a TW sensor and Thermostat & gasket on the bill, so I assume he did some sort of system flush. Currently I am using the OEM cap as well, as Ben broke the fancy chrome one and my attempt to fix it with silicone adhesive has failed ( ). Since getting it back, I haven't noticed any spill over but I figured it would be something I would use the nifty new OBDII toy to keep tabs on. I will also be sure to ask if a full coolant flush was done when I do sit down and get some time to talk with Ben.

 

[nsxnut]

Great thread, I appreciate everyone who has chimed in! Nothing like learning a few new tricks and getting some good advice.

The coolant spilling over is exactly what I was experiencing (photo below). I thought it was simply a bad seal with the cap as it is an aftermarket coolant tank, but all the gaskets were in good shape and it appeared to be connected properly. I had the car at Daisy auto, and I think he did a full coolant flush but Ben has been pretty busy so I haven't gotten really detailed run down on what he did. There are 3 bottles of Honda coolant, a TW sensor and Thermostat & gasket on the bill, so I assume he did some sort of system flush. Currently I am using the OEM cap as well, as Ben broke the fancy chrome one and my attempt to fix it with silicone adhesive has failed ( ). Since getting it back, I haven't noticed any spill over but I figured it would be something I would use the nifty new OBDII toy to keep tabs on. I will also be sure to ask if a full coolant flush was done when I do sit down and get some time to talk with Ben.

Are you completely filling the expansion tank?

You need some air to absorb the volume change due to thermal expansion of the coolant. Aka room temp to operating temp.

http://answers.yahoo.com/question/index?qid=20100429193632AAsGpxM

 

[blue_myriddn]

Just as a follow up, the OBDII reader registered between 178-196, with values most often hovering around 183. So that was reassuring. Only spiked up to the 190s when I was sitting in traffic, which makes sense as there is no airflow.

I had fun with the OBDII thingy, was neat to have diagnostics at my fingertips.

*edit*
"Are you completely filling the expansion tank?"
Nope - leaving room at the top. The Dali tank is two chambered (from what I can see) and the top chamber always appears empty when I look in it, while the bottom chamber is full. I am assuming that is "normal"