These are the facts!
If the EGR cooler is removed and center head fitting capped and all hoses removed and you have a failed totally open OEM thermostat which means the bypass valve within the thermostat is fully closed all the time allowing
NO flow through it.
IF you have installed an in-line thermostat. There is
NO FLOW through the head until such time heat can migrate through the coolant to the in-line thermostat and start it to opening allowing some flow to take place from the head into the radiator.
This means that the coolant in the head is totally stagnant (stopped, deadheaded) during every warmup cycle of operation of the engine and who knows what kind of temperatures the head and / or head gasket are subjected to before any flow begins to take place. (HOTSPOTS)
As to the oil cooler, the flow through it comes off the water pump discharge and is returned stright back into the water pump suction so it's flow has absolutely nothing to do with coolant flow through the head.
As to the flow off the thermostat to the viscous heater and heater core, this allowed flow is extremely small through the head, it simply returns to the water pump suction. Due to hose sizing and flow rates that are very restricted through the viscous heater and then the heater core, it may not provide sufficient enough flow through the head during the critical warm up cycles to protect the head from possible hot spots or overheating. (edit)
As to the vent off the thermostat back to the degasser tank, it is simply a vent to allow any air or gases to vent back to the degasser tank by design. Again this flow never allows any flow through the head ever.
I stand by my earlier statement!Installing an in-line thermostat is a very, very bad and risky modification for this engine due to it's coolant flow design if it has a failed OEM thermostat due to the facts above.
Anyone doing so is taking a monumental and possibly a very expensive risk! But it is your vehicle, to each his own, you can do whatever you desire.
I for one would never recommend doing this mod to a Jeep CRD no matter what anyone on this forum tells you!!!!To understand the coolant flow of this engine, please study the coolant flow diagram below I drew and I believe most will fully understand the ramifications of why not to ever do this...
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Supporting Vendor and Moderator of LOST05 Jeep Liberty CRD Limited
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