I've read a lot of discussion on the issues with the thermostat, including the cost, the lack of choices of thermostat temps, and reliability.

Is anyone familiar with using in-line thermostats? I did not know such a thing existed until I thought of the idea and Googled it. Turns out that Summit sells such a beast:

http://www.summitracing.com/parts/MEZ-WN0071

I'm still looking at applications online where people are using them, but so far it is gassers trying to get their temps down. Seems like in our case we could put in in and put a higher temp thermostat in it and hold back the flow until the higher temp was reached.

BUT, I don't really understand how these can work, since the water flow isn't passing over them constantly and they are so removed from the engine heat.

Anyone familiar with them?

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2005 Silver CRD Limited
4 year MaxCare warranty, so completely stock

Stay with the original thermostat or Mark's modified one. They have a required bypass port that you wouldn't get with an inline. For all the modifications you would need to make to remove the oem device (you wouldn't want to leave a non-functioning one in), you might as well get one of Mark's.

It has been tried, and failed http://www.greendieselengineering.com/f ... st/69.page

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20 year owner of Libby CRD!
2006 LTD Bright Silver loaded with all the needed mods, CCV intact.
Equipped with HDS thermostat, plenty of heat, faster warm-ups, increased fuel mileage.

Another consideration is that our 2.8L VM CRDs have wet sleeves as opposed to the newer parent bore block. As a rule as the cylinder walls get thicker the lower the engine operating temp needs to be and with thicker cylinder walls the coolant temp needs to be higher. Add to that the CRD has an aluminum head which expands ~ 2X as much as a cast iron head, that is why we have torque to yield head bolts to compensate for the expansion and not trash the head gasket like early VW IDI diesels did.
In "THEORY" one could change out the coolant to straight propylene glycol, go to a zero pressure system, and make a 275f thermostat and greatly increase the efficiency, some MB 300 D inline 5 cylinder engines have pulled it off. If you had several sacrificial engines to test, you may be able to work out all the bugs like the effect of the injection system, glow plugs, ECM tuning, on, and on. But, like many theory's, they are built on assumptions and the assumptions need to be transformed into reality. With all the pressure auto manufactures to increase fuel economy, if it were practical, VM would have done it.
If anyone wants to turn a theory into fact, knock your self out

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2006 Pearl Green CRD
Magnaflow 2 1/2" Cat Back
KJ Extra Leg Room Brackets, Carter Lift Pump, V6 Airbox, ORM
Fuel cooler, Oil Separator, Progard 7
Gauges EGT Boost Trans Temp Oil Pres, Michelin LXT AT2 245 70 R16
7,000# Draw Tight hitch, PML EX Deep Trans Pan
Centrifuge, SunCoast, Transgo, RAM TCM, InMotion Stage 2
Wife's 99 TDI VW Beetle

Thanks for the link. I don't see the failure, though. He got it working, then stopped posting. His results good, but inconclusive because he changed other things (removed his fan) at the same time.

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2005 Silver CRD Limited
4 year MaxCare warranty, so completely stock

Yeah there had to be some kind of tradeoff in longevity or something. Or maybe they just didn't want to make another proprietary thermostat at a different temperature, since they already made up 10,000 of them sitting in the warehouse. Or the tradeoff may have been in emissions results, which may have trumped fuel efficiency at the time. We don't know if the temp was set by VM or DC, do we?

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2005 Silver CRD Limited
4 year MaxCare warranty, so completely stock

Could be the plastic radiator/heater core tanks could not take it in high desert heat, so they opted for the ~176f thermostat. We don't know, all we can do is speculate.

_________________
2006 Pearl Green CRD
Magnaflow 2 1/2" Cat Back
KJ Extra Leg Room Brackets, Carter Lift Pump, V6 Airbox, ORM
Fuel cooler, Oil Separator, Progard 7
Gauges EGT Boost Trans Temp Oil Pres, Michelin LXT AT2 245 70 R16
7,000# Draw Tight hitch, PML EX Deep Trans Pan
Centrifuge, SunCoast, Transgo, RAM TCM, InMotion Stage 2
Wife's 99 TDI VW Beetle

I guess I fell out of the loop and forgot all I posted on the topic myself? I will have to keep that option in mind if I ever need a tstat.

_________________
20 year owner of Libby CRD!
2006 LTD Bright Silver loaded with all the needed mods, CCV intact.
Equipped with HDS thermostat, plenty of heat, faster warm-ups, increased fuel mileage.