Thermostat doesn't seem to open.

[slipnfall]

Hi, I have a feeling my thermostat isn't opening in my rebuilt DE. I let the car (S13 BTW) warm up for a good 15mins, with the rad cap off. The lower radiator hose will not get hot at all, while the top one is very. I watched the filler neck for fluid to start 'flowing', but it just rose to the top. I should see the fluid flowing when it opens, right(like a stream passing under the filler cap)?

The rad gets very hot. The temp gauge seems to function properly, goes from cold to ~60% of full scale. I'v only had it overheat once, at the end of my first test drive, so I bleed it again(w/heater on full) and it hasn't happened since.

New radiator, pump, thermostat, even engine coolant temp sensor(the two-pronged one). I followed my Haynes on thermostat installation. The cabin heater works fine.

So what's the deal here? Is the other temp sensor for the temp gauge? I really don't want to ruin this engine, so any help would be appreciated!

Thanks much,-Jamie

[s13sr20chris]

oem thermostat? i specify because i have seen big name brand aftermarket thermostats stick too many times. have you bled the air out of the system? try revving the motor occassionally while burping the coolant and see if that helps. a cold lower hose just means the radiator cooled the coolant off really well for some reason. that could be due to a sticking thermostat but it could just be due to air or slow moving water getting cooled off in the radiator.

[slipnfall]

Advanced Auto Parts(mid/east coast chain) brand. It was like $7-8. Am I correct about the visual indication of the thermostat open(flowing under the filler neck)? That stock clutch fan really does move some air! I just find it odd that the top of the rad will burn me, along w/the upper hose, but the bottom hose is cold. I'll check next time after I take a drive.

BTW, why are there two temperature sensors on the intake mani? Is one for the ECU, and the other for the dash gauge? Seems kinda redundant if that's the case.

Thanks Chris,-Jamie

[Nismo_Freak]

Advanced Auto Parts(mid/east coast chain) brand. It was like $7-8. Am I correct about the visual indication of the thermostat open(flowing under the filler neck)? That stock clutch fan really does move some air! I just find it odd that the top of the rad will burn me, along w/the upper hose, but the bottom hose is cold. I'll check next time after I take a drive.

BTW, why are there two temperature sensors on the intake mani? Is one for the ECU, and the other for the dash gauge? Seems kinda redundant if that's the case.

Thanks Chris,-Jamie

The larger one is the ECU coolant temp sensor and the other is the gauge cluster sensor.

A good test (read: lazy haha) for the thermostat is to drive around on a cold night and turn the heater on full blast. If the engine temps drop rapidly down below normal (like almost down to C) then you more than likely have a stuck thermostat.

Honestly I'd just go buy a nice stock thermostat from Nissan and replace the one you got. It's cheap.

[NISTECH]

I just had a S-14 in for the same exact problem, the owner of the car had done everything you just did. turned out his aftermarket thermostat was the problem. His was a cheap one though it didnt have a bleeder hole in it as the factory one does. 240's tend to be difficult to purge air from when dropping the coolant from the block ,ie when replacing the water pump or cyl head work. using a bleed funnel from the local parts house tends to help getting it blead properly.

[slipnfall]

Just picked up and OEM one. It was $12, but it certainly looks a lot better than the one I have in now. This one feels like it weighs twice as much: certainly beefier. Not that I didn't trust it, but from now on I'm going to boil my tstats before installing them. I could have saved myself alot of trouble if that indeed is the case. Either way I'll feel a little better knowing it works.

I drove around for about a half hour this morning to get the engine nice and warm. Since i have my AC removed, I put my hand directly on the radiator core:Top was really hot.Middle was warm(rough guess is 70F)Bottom was definately cold. Not as cold as body parts, but cold.

Outside temp today is around 40-45F.

I'll try to get this new tstat installed this weekend. I had some problems with the aftermarket one even fitting right: I had to really goop on the RTV around the edge to keep it from rattling in the housing.

Thanks NISTECH.-Jamie

[mtmetzger]

Did the OEM t-stat fix your problems? I have been experiencing the same problems with my S13 ever since I changed the water pump. The t-stat was not opening. I replaced it with a cheap aftermarket one and it did the same thing. I pulled it out all together to verify that the engine would stay cool with out a t-stat and it did. I just installed an OEM one last night, pulled the bleeder screw, and filled the system. It is still sticking closed!!! Do I need to do something special to bleed the system? Any advise will be appreciated!! Thanks!

[slipnfall]

Are you sure you installed it in the right direction? Also the bleeder hole on the tstat has to be installed upwards. Other than that, I suggest boiling thermostats before installing them... it's 10minutes that can save you 30mins later.

HTHJamie