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It's starting to get cold here in Missouri and my check engine light just came on. So I run the code and it relates to the thermostat not working correctly, I also noticed that the gauge was lower than it was in the summertime. Well a few days later it was 12 degrees in the morning and the coolant temp gauge would only go up two bars which means just enough heat to defrost the windshield and take the chill off. (Thank God for heated seats) So this weekend I decided to install a Gates 33912 replacement that cost just under $20 shipped. I pulled my driver side air box / MAF tube and also the cam cover so I would have room to see. Next I pulled the lower radiator hose and drained the coolant, then removed the 3x 10mm thermostat housing bolts and removed it. The factory thermostat has a rubber type seal around the plunger, it was distorted and falling apart holding the thermostat open so it wouldn't get to full temp as it got colder outside. The new thermostat is built like the old classic type metal to metal. As I installed the replacement thermostat I reused the MLS type factory metal gasket instead of the paper type that came with the replacement. I put the 3x 10mm bolts in and when they bottomed the thermostat was still loose??? So I pulled it back out and measured everything to see why the factory bolts wouldn't work. Well the new thermostat housing is thinner than stock so you end up with 6mm + too long of bolts. If I were to torque them down not paying attention it would have stripped them out and or broke the aluminum on the head side. So I measured the bolts and used a angle grinder to cut them down and then used a belt sander to round the tips so the threads would go in smooth. I tested the bolts with a 10mm nut before using them in the aluminum so I wouldn't damage any threads.
I thought I would put this install warning out there so this doesn't happen to anyone else. Here is a link to another user here that bought a car with the exact problem and they destroyed the mount holes in the head trying to install a thermostat:
Replacement thermostat Cut down bolt New vs Old Original length Length on new housing = too long New vs Old New thermostat Old housing - Damaged rubber seal is the problem Removed cam cover for clearance
Last edited by scumbagsleeper; Nov 18, 2019 at 01:37 PM.
I was changing it out last weekend and when I got to installing the bolts and they bottomed out I instantly thought about your thread. I hope your car is still going good after the repair.
It's been good so far but had some coolant loss recently, first assumed the worst because I couldn't find a external leak but finally found it and it was a thermostat bolt that was leaking. Tightened it a bit more and it seems good so far.
This is a warning about any aftermarket thermostat. They should be visually checked and measured before install. The one I installed was a Gates 33912. The factory PN# 21200JK20A will fit fine but will probably fail again because of the stupid rubber seal on the plunger. The aftermarket thermostats are not built like that.
Garnet Ember G35X Sport EBC rotors LEDs GTR button Tail-as-Turn TBW undertray Alarm shock sensor
Just a guess ( I haven't replaced my thermostat yet as it is working fine) but does Gates and other aftermarket venders assume there are washers (lock washers?) that go on the theromostat housing bolts to keep them from bottoming out?
Yeah but even aftermarket components are dimensionally the same.
@scumbagsleeper I'm curious to see if the bolts you pulled off the engine are actually the correct 11916-JK23A bolts for the HR motor or if somehow it was assembled with (or previous mechanic replaced with) the 11916-31U0B bolts from the DE motor.
I know those HR thermostat bolts are SUPPOSED to be shorter than the DE bolts and I could have sworn they were a full-thread bolt and didn't have a shoulder on them like the bolt you took a picture of. I'm not aware of any thermostat housing revision for the HR but I've never actually LOOKED before. Possibly Nissan switched housings sometime during production and the later revisions actually were thinner flanged?
I doubt that the thermostat was ever changed before. The car only had 124k on it when I bought it. Hopefully more people will chime in as they change out the thermostat from failure so we can get more info. I may pull one bolt out of my brothers 08' G35x and see if his has the same bolt.
