2 thermostats! pics

[ken in az]

After logging multiple runs with the Cipher software I noticed the coolant temps were out of this world. Running around town 203F - 215F temps!!!!

I'm not over heating by any stretch of the imagination but to me those temps are high. I'm used to 180ish to 190ish temps cruising around.

So after visiting the titan forums it looks like an old 300zx thermostat rated at 170F works perfectly when you cut the cage off the back. the titan guys report 183-190deg temps which is right where I'd like to be. After cross referencing part numbers it looks like the stock titan thermostat is the same part as the M45 so I did the swap. Super easy and only took literally 5 minutes and a slight top off of coolant.

Went for another drive and temps were slightly better but still gets pretty hot. I was thinking WTF Then I remembered that the M45 actually has 2 thermostats - one in the front and one in the rear of the engine under the intake manifold that is called the "water control valve" Found out that it is rated at 95deg C which is exactly 203deg F

So off to the parts counter - measured the stock thermostat and went to chesker to see if they had any generic thermostat's that open at a cooler temperature.

Found a Murray 160deg F thermostat that was darn near identical, only slight modification for it to fit. It was 1mm to large in diamter so I ground it smaller and added a burp hole like the stock thermostat and viola - perfect.

Got everything back together and went for a drive and the temps would get into the high 195-198 range but when I would crack the throttle and accellerate the temps would climb right back up to the 203-210deg F range.

Thinking now I parked in the driveway and watched the temps and listened to the cooling fan. Sure enough the cooling fan kicks on right at exactly 208deg F and shuts off at 203deg F.

When I turn on the AC (the AC kicks on one of the fans to prevent overheating of the ac system) and with that fan on the temps drop to 195F so now it is my quest to trick the fans into turning on sooner.

The first pic shows the engine without the intake manifold, there is the front thermostat housing just under the radiator cap. It's the black housing connected to the big hose there in the front of the engine.

The rear thermostat is in the rearmost center of the engine where those aluminum pipes connect to the cylinder heads.



This is a top down photo of the rear thermostat housing techincally called the water control valve.

[uknown4now]

Are the thermostats the same for front and rear or do they take different PNs?

[jiggersplat]

Why do you want to run at a lower temperature than designed? You may lose some fuel efficiency.

[BlackCat81]

205 is pretty ideal for most cars. Tricking the second fan to be on all the time will be loud, and may also trigger some codes for coolant temp threshold.