QR25DE cooling question

[OrangeUaVol]

Okay, like a few other people on here...I am displaced from MSV. MSV had a bunch of useful information about the QR motor. I read on MSV that the QR has two thermostats. One opens at 177 degrees and the other at 200 degrees. The one that opens at 200 degrees is actually not a thermostat. According to Nissan, it is a water control valve.

The water control valve allows the head to run hotter than than block, supposedly for better emissions. But whatever, emissions are not my concern. Some people have claimed that running the head hotter than the block could possibly be a culprit to a blown head gasket. A few people have gutted their water control valve, allowing the head to run at the same temperature as the block. I don't know if it is such a good idea to gut out the water control valve, allowing for coolant to free flow into the head.

I, on the other hand, would like to run a thermostat (that opens at 177 degrees) in place of the water control valve. However, I am unsure if the two different parts are the same diameter. In essence, I do not want to gut the water control valve, but rather replace it with another thermostat...so both the block and the head are running at the same temperature.

Now that MSV is down, I don't have access to their information. Anyone have any ideas of what I can do so that I can run the block and head at the same temperature?

[SERious reSPECt]

sounds interesting! i would also want to look into this!!!! Bumpz

[nametakennow]

Interesting concept. I'll see if I can woo one of our Nissan Techs in here to lend some insight on the idea.

[OrangeUaVol]

So I flushed and filled my coolant...and during the process found that the thermo in the block will not fit in place of the water control valve. So I took out the water control valve altogether, but reused the O-ring from the water control valve to ensure no leaks.

Now the coolant can flow into the head without waiting for the head to reach 200 degrees...so now the block and head are both running at 177 degrees essentially.

I buttoned everything back together and noticed a small drop in the normal op temp of the motor.

[Classic_Fetish]

your water temp. gauge sending unit is typicaly mounted off the head not the block, so by allowing the cooler water to flow through the head your going to see a lower temperature at the gauge...

also, adding in the second thermostat really seems like just another part to go wrong... as long as the water control valve was proceeded by the original thermostat, then water going through the head should be regulated by the thermostat just as well as the block is with the WCV gutted

the only concern i could see is the now undisrupted water flow trough the head could be actualy running the head cooler than the block... i would use an infared temp gun and make sure your not looking at any major discrepencies throughout the engine