I just installed a lower radiator hose heater I bought from NAPA (looks similar to the one offered by diesel giant). After I wrestled the hose onto the both sides of the heater and reinstalled the hose, I looked at how the water flows. This heater will heat the water in the radiator and up to the t-stat. But the t-stat will be closed, so how can it warm the engine block? It must somehow right? Its driving me bonkers and I was so excited to have a warm engine engine for the rest of thie winter...

Can anyone explain it to me?

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1985 300TD-euro 352,000 mi
1974 240D (1?)52,000 mi - has a new home now

As far as I can tell a small amount of warmed coolant will circulate past the bypass at the thermostat at all times and through convective currents it will warm the coolant some in the engine. Not as effective as a block heater, but you probably knew that.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

when the stat reaches its opening temp it will open and circulate to the block. they arent as good as a block heater but are a lot better than nothing and a whole lot easier to install.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Was it the 1 1/2 version? I have one but have yet to install it.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

When I use mine it makes a huuge difference in cranking time when its super cold out. I can fire up my engine with a 10 second glow and 2-3 cranks if I use my heater overnight, even if it is like -10F outside. Without it its hit or miss if it will start at those temps...for my car anyways. Sometimes it will, a few occassions it hasn't.

Leaving mine on melts all the snow off the front of my hood/grille, warms the front of the engine, lower hose, and T-stat....it warms it pretty good, especially if left on overnight, which is what I usually do.

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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

yes, I'm pretty sure it was the 1 1/2". Getting the lower hose connection off without laying down in the slush on my back was tricky, but the only real hard part was muscling the hose on the heater.

I didn't think the heater would heat the water over 180*F to open the t-stat. Maybe it will...

Does the engine oil go though the radiator? I suppose that oil may get heated in the radiator from the water in there but that seems like it would take forever.

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1985 300TD-euro 352,000 mi
1974 240D (1?)52,000 mi - has a new home now

the engine oil does not go thru the rad but it will be somewhat warmed by the heater.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

I have a lower hose heater about 2 inches from the thermostat housing.
Thermostat housing gets hotter than hell. Heats by convection, I guess water on the other side of the thermostat is heated by the housing itself.
When the car is facing the wind it doesn't seem to retain the heat as well.
1 crank at -5 F and she's going as long as the wind is coming from the back of the car, not blowing away the heat.
Temperature Gauge reads a little below 40 on cold mornings.

If I understand correctly, the water pump is running all the time. Yet with the t'stat closed will not circulate cooled water, as it is trying to draw against a closed "door". Once said "door" is opened, coolness ensuses. A heater on the lower hose with engine off, will warm all water in engine, albeit not very effectively, as heat moves upward. There is no "switch", t'stat, on lower hose, so it is always open.

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83 SD

84 CD