I also have that restrictor fitting, from Leroy Diesel, installed on the coolant pump bypass fitting.
Restricts some of the coolant from flowing straight back to the radiator.
That might help with internal temps too.
NO- bad description or misunderstanding here.
Without the restriction fitting AND a non bybass blocking thermostat, which there are some single and all dual thermostat crossovers without block off plate:
The hose that goes from the crossover back down to the waterpump is unrestricted so all that water goes from waterpump to block around cylinders then at the rear go up to the heads. Go foreward across the head and through the crossover. From there it is ready tomgl to the radiator but thermostat is closed. So it goes through the hose to the waterpump and meeps recirculating.
When the thermostat opens up about 3/4 of it goes to the radiator and 1/4 of it continues to go through that short hose back to the waterpump and keeps recirculating. Your 200° coolant goes to the radiator and gets cooled to say 170°, goes up the lower radiator hose and into the waterpump where it mixes with 25% water at OVER 200°.
For cooling purposes it is a horrible design- outright stupid. Thats why the block off thermostat was created. The water has to circulate in the engine from the mechanical water pump- so non bypassing thermostat has to have a circulation route or it will cavitate and aerate the water. Ever look at the backing plate for the waterpump and it’s all “chewed up” or “divits of metal missing”? That is from cavitation. Even with the stupid recirculating hose and no bypass that hose being less than half the size means a restriction in flow causing cavitation.
The restrictor fitting does NOT restrict water from going to the radiator. It restricts water from recirculating in the engine and forces it to the radiator so that a larger percentage of the water gets cooled off, and there is less fully heated water in the pump to mix in and heat up the cool water.
There is a negative effect - the backing plate will get pitting a little faster but that is a minor issue compared to ruining the heads, pistons, rings, and block. I experimented with silicone to smooth the pitted plate- bad choice. The cavitation gets strips is clean and now debris is in the system. Same for powder coat- don’t do it.
As to Leroy not mentioning twin stat crossover- that is because the original restriction fitting was done on engines with single stat crossover that wasn’t block off aka bypass style thermostats.
The creation of the dual thermostat housing not being bypass is an absurd error.
Many people learned to replace the dual crossover for the older single with bypass unit. The problem is the accessories get in the way for most - this is why the rare 1996 part is so desirable- single stat crossover that fits the newer trucks.
Look at the block off option link in my signature for better cooling but no rare 96 crossover handy… but if your heat is under control, don’t bother.
When wanting the truck to heat up faster- the recirculating coolant is desirable. But this is simply the thermostat stays closed and it recirculates all except the thermostat weep hole. And since there is one per stat- the dual one does a worse job.
A higher opening temp of the thermostat(s) helps to force hotter recirculating temp
So I have heard of guys with duals running 1-180 & 1-195 attempting a happy medium for winter time.
Most the guys who want heat and longer engine life buy a comfort heater from Wabasto. Make the engine run cool and live long, burn a little extra fuel for cozy factor.
