water temperature problem

[Martin_VTEC]

Hello,

I took my NSX out for a spin, for about 20 km, not riding very hard. when I returned home, let it run idle for 5 minutes, the water temp was still in the middle.
then in just 20 seconds the temperute was going up almost in the red area.

The fan wasn't blowing by my radiator and the little fan in the engine-compartment wasn't spinning either...

I can't see any leaks, there is not coming any white smoke out of the exhaust. The engine is running fine

Is this just a bad thermostat ? or 1 faulty TW-sensor ?

please help

 

[goldNSX]

On the NSX the thermostat normally keeps open. Changing it is the cheaper culprit than changing the headgaskets. A sniffer test could tell you if the headgaskets are bad.

 

[Martin_VTEC]

But how can it be that the fan won't go on ?
a month ago it did go on, no it's not
I did have this problem 1 time before a few years ago

 

[Martin_VTEC]

I think i should ad that 2 years ago , the coolant hose from the oil-cooler was coming off and lost all my coolant while driving. and the temp-water was going all the way up.

I was towed back home and replaced the hose clamp and filled the engine wit Honda coolant and bleed the system.
Never had problems with the water temp again until now.

 

[pgilliam1]

If the fans are not coming on then you'd assume it's a bad sensor telling your guage something that isn't true. A bad thermostat usually causes long engine warm up times. I've used 2 words, assume and usually, that shouldn't be used when high engine temps on this car are in question (overheating this engine is a real bad thing). How long has it been since you replaced the thermostat (it's a good idea to replace the OEM stat because they are a known problem - however it may not be the problem)? Did the engine compartment seem really hot when the guage was near red? Changing the temp guage sending unit is not that hard or exspensive.
Good Luck!

 

[Martin_VTEC]

I don't know when or if the thermostat has ever been replaced.
I bought the car with 192.000 km, and it has done 197.000 km at this point after 3 years ownership. and it hasn't been replaced in the last 3 years.

The engine didn't seem that really hot.

But u mean that a faulty thermostat generally causes long engine warm up times. Never any overheating ?
Can I check the temp or bypass the gauge in my dash to see the actual temperature ?

 

[goldNSX]

Sorry, I've overread that the fan is not coming on. It should if the car stands still (no air blows through the radiator). Check the fuse, fan and sensor. This could be a simple solution before you do anything else.

My car needs about 1 or 2 minutes or so after a extended drive to activate the fan.

 

[Martin_VTEC]

Ok, I wil check the fuse tomorrow, but how can I check the fan and sensor ? where is the senor located ?

 

[goldNSX]

Ok, I wil check the fuse tomorrow, but how can I check the fan and sensor ? where is the senor located ?

Have a look in the SM for the location of the sensor. For the fan, check the resistance at the plug. I'm not sure but I saw a resistor behind the radiator too. Check all of the components involved with a multimeter.

 

[EdinKali]

If all the fan stuff checks out might be worth bleeding the system to see if you have any air pockets. An air pocket can cause the temp to spike really quick like that.

 

[comtec]

First thing i would do is check the fluid level in the radiator when the system is cold. Not just the expansion tank but the actual radiator.

Do the power mirrors work? If so then the fuse should be good, they use the same one.

Be aware that the radiator fan control sensor and the coolant temperature gauge sending unit are different. The coolant temperature gauge sending unit controls the gauge on 91-99 cars.

Mike

 

[Martin_VTEC]

checked the fuse in the fusebox by the spare-wheel and it's ok.
It is a 30A fuse and according to the diagram it's only controlling the fan , not the power mirrors.

I don't have a multimeter , i wil buy 1 tomorrow after work.

I can go to the garage and let them bleed the system, but that doesn't explain why the fan isn't working...

This car is really becoming a problem child from day 1.

 

[goldNSX]

I don't have a multimeter , i wil buy 1 tomorrow after work.

I can go to the garage and let them bleed the system, but that doesn't explain why the fan isn't working...

Good decision. A simple and cheap multimeter which reads volts and resistance is sufficient.
Good decision 2. Check the fan first, it's cheap to do so. What you can do is shorting the sensor switch and see if the fan is running. If not -> measure the voltage at the fan plug with the sensor switch shortened. If no voltage the problem is earlier in the electric diagram. Not sure but I think there's a relais for the fan as well.

 

[Martin_VTEC]

Thank u, i will do that.

I took another look under the bonnet and noticed this:



green substance , so probably coolant, posably from the white plug, but around the white plug it's dry.

 

[goldNSX]

green substance , so probably coolant, posably from the white plug, but around the white plug it's dry.

Change the o-ring of the white plug, the one of the lower plug too. Check coolant level. Check the coolant system, maybe it not a bad idea to change the hoses if they haven't been done so far.

Wash the front compartment.

 

[Martin_VTEC]

Coolant level is OK, but this can't cause air in the system right ?

and yes, the front compartment is dirty :tongue:

 

[goldNSX]

As the coolant system is pressurized it's more likely to have a leak than an air-pocket due a failing o-ring.

 

[comtec]

checked the fuse in the fusebox by the spare-wheel and it's ok.
It is a 30A fuse and according to the diagram it's only controlling the fan , not the power mirrors.

I don't have a multimeter , i wil buy 1 tomorrow after work.

I can go to the garage and let them bleed the system, but that doesn't explain why the fan isn't working...

This car is really becoming a problem child from day 1.

In the dash fuse box Fuse #4 powers the cooling fan control unit along with 19 other items, one of which is the power mirrors :wink:.

 

[Martin_VTEC]

@GoldNSX:
I'm going to order 2 plugs and O-rings right now, it's just a small puddle of coolant, the coolant level in the reservoir in the engine-compartment hasn't changed.
So U say that this little leak could cause this overheating ?? :smile:

@Comtec:
I will check that fuse right away when i'm home from work, I did check the fuse of the little fan in the engine compartment, it was ok, and that fan also didn't do it last week

 

[goldNSX]

@GoldNSX:
I'm going to order 2 plugs and O-rings right now, it's just a small puddle of coolant, the coolant level in the reservoir in the engine-compartment hasn't changed.
So U say that this little leak could cause this overheating ?? :smile

No need to order the plugs, just the o-rings. You can change them without draining the whole coolant system if you're quick. :wink: Bleeding afterwards is still advisable.

No, the fan not running is causing your overheating, most likely.

BTW, the coolant system is a pressurized and closed system. Leaks like this have the consequence that the system can't build up pressure which lowers the boiling point of the coolant which can be observed under very hard driving condition (track, german autobahn). For me it was on he later one. Many people break their head about WHERE the system is loosing pressure after having changed other parts. Those o-rings are the culprit. There are other o-rings around the engine but they don't leak normally.

 

[Martin_VTEC]

thanks, I called the honda-dealer 1 hour ago, have ordered the plugs also, no harm :smile:

I will give feedback as soon as possible when I :

-measured the sensors, the resitance of the fan-plug and check the fuse
-Replaced the O-rings and fill any lost coolant
-bleed the system

and after that a compression test to check if my head-gaskets are good

After checking al these points, maybe replacing the thermostat

 

[comtec]

Martin,
First thing i would worry about would be why the fans aren't working. I think that is your main problem.

Did you say you checked the fluid level inside the radiator and not just the reservoir?

Mike

 

[Martin_VTEC]

Mike,
I will do that like I mentioned in the post above:smile::

-measured the sensors, the resitance of the fan-plug and check the fuse

When the fan is running the following things will be done:
-Replaced the O-rings and fill any lost coolant
-bleed the system

I checked the fluid level in the reservoir in the engine-compartment, how can i check the level in de radiator ?

 

[goldNSX]

If the radiator has a leak at the top it obviously doesn't have an air pocket. :wink:

 

[comtec]

Mike,
I will do that like I mentioned in the post above:smile::

-measured the sensors, the resitance of the fan-plug and check the fuse

When the fan is running the following things will be done:
-Replaced the O-rings and fill any lost coolant
-bleed the system

I checked the fluid level in the reservoir in the engine-compartment, how can i check the level in de radiator ?

I don't think you can, don't know what i was thinking :redface:.

Mike