Heating the transmission with engine coolant

[Daox]

Originally Posted by JBarr

So would you set the thermostat so that it will dump heat to the transmission before the thermostat to the radiator opens? If you transfer the heat through the transmission case it won't be the most efficient method, but it will be simple and not require serious modifications. If it is done cheaply the improvement may be worth it.

Yep, thats the plan.

[Daox]

Originally Posted by Old Tele man

Recondition: heater control value from wreck

What cars use electronic solenoid valves for heater control valves?

[2000mc]

I think a lot of European built cars do, which should make it a bit trickier to find in a junkyard. Saw one on eBay for a s class for $24, but they didn't cut off the electrical connector to sell with it, which makes it not such a deal... Anyways I think you could probably get one off some random BMW or Mercedes

[Daox]

Thanks. I checked out ebay, and they have some okay prices. Here is one example:

1992 Mercedes Benz 300 TE 3 0L Heater Control Valve 001 880 20 84 | eBay





This one even looks like it has a pump embedded:

00 06 Mercedes W220 S500 CL500 Auxiliary Heater Control Valve Water 2208300084 | eBay

[2000mc]

One with a pump would be awesome, I'm just worried buying new connectors will cost a lot more than the used component

[Daox]

Haha, quite true...

If you do a search for "12v solenoid valve water" on ebay, you'll come up with a bunch of other options though that are actually cheaper (though probably not as reliable).

Here is an example:

[Daox]

Some more insight and proof I'm not totally off track.

Thermal management improves Ram 1500 fuel economy and earns EPA off-cycle credits - SAE International

The Ram features an active transmission warm-up system with an oil-coolant heat exchanger on the transmission. The hoses are connected to the engine cooling system. Although this is one of the items eligible for the EPA-proposed off-cycle CAFE carbon credits (corporate average fuel economy), Chrysler integration engineer Jamie Standring said it was in the original engineering plan for the Ram program to provide best-in-class fuel economy.

The engine cooling circuit has both a three-way valve for coolant and a bypass valve in the transmission oil cooling circuit so the transmission oil can be warmed up more quickly from a cold start, which reduces parasitic loss from the drag of the spinning gears. If the transmission oil is getting too hot, such as during towing, the bypass valve setup directs oil from the heat exchanger and into the transmission cooler in the front-end cooling module.

[2000mc]

Originally Posted by Daox

Haha, quite true...

If you do a search for "12v solenoid valve water" on ebay, you'll come up with a bunch of other options though that are actually cheaper (though probably not as reliable).

Here is an example:

3 4" Electric Solenoid Valve NSF61 Potable Water 12VDC 24VDC Vac 110 120VAC G28E | eBay
Like most diaphragm-type valves, this valve requires minimum pressure (5 psi) to open. It is intended to be used in pressurized systems, not in gravity feed systems. The pressure may come from city water pressure, well pump etc.

[Rrrrandy]

I agree: use ATF and let stay cold.
Then drain & refill w/gear oil for warm weather

[paulgato]

1. A mechanic once wrecked my manual transmission by filling it with ATF instead of gear oil after a clutch change job. (The original gear oil was coloured red so he thought it was ATF and didn't bother looking it up in the book.) I realised the error and got it swapped out for gear oil after 100 miles or so, but the damage was done. Gearbox was always noisy after that. It worked OK, but it whined badly. Gearboxes are not all the same, and you experiment with wrong lubricants at your peril. The original Minis had a combined gearbox and engine and they both therefore ran on standard engine oil, which got changed out at every service.

2. I have a 2002 diesel VW Golf Estate, manual transmission. VW say the gear oil never needs changing. After 150,000 miles and at ten years old, I decided to change it anyway. I used the (synthetic) stuff VW recommend and sell for that gearbox, plus I added a small tube of Molyslip gearbox additive (watch out - I believe the 'Molyslip' available in North America is different from that available in the UK, where I am). The difference in rolling resistance was immediately obvious. A very cheap and quick 'mod' and very worthwhile. Conclusion: this story VW tell about transmission oil never needing to be changed is utter *****, probably designed more to sell new cars than to help owners of old ones.

3. You were talking about fitting some kind of temperature-sensitive switch-over device, but you already have one of those. It's called a coolant thermostat. Why not simply run the gearbox heater in line with (or in parallel with) the radiator hose, and block the airflow to the radiator? Always better to prioritise engine heating until engine design temperature is reached.

4. How about helping things along by not only insulating the engine but also insulating the clutch and gearbox? That might help even with the normal heating (by conduction and friction) but if you are running coolant to the gearbox then there is no risk of ever overheating a fully-insulated transmission as the coolant will cool it as well as heat it.

5. Earlier this year I fitted a 240v coolant heater and pump, which I switch on from inside the house with a little radio control keyfob unit an hour or so before driving off. I thought about adding a small 240v self-adhesive transmission heater pad but never did. (Maybe I could use a coolant-powered one instead. Hmmm - built-in thermostat - I like it. I can just link it into the existing hose run from the pre-heater.)

My 2kW mains engine pre-heater gets the engine up to about 70 degrees C or so. (Normal running temp is 92 degrees.) The preheater thermostat actually switches the heater off (but pump still runs) at 85 degrees and back on at 75 degrees, but once the engine is started the temp immediately drops down to about 70 degrees. Still, that's a very useful degree of pre-heating and mpg is much better over the first few miles than it used to be. However, even with a thoroughly pre-warmed engine, and even in summer, if I go on a longer journey the mpg creeps up and continues to increase for about two hours, and then plateaus. My guess is that everything is warming up - engine, gearbox, driveshafts, CV joints, wheel bearings, tyres - and it takes two full hours to achieve maximum temperature, and therefore maximum mpg.

6. My hunch is that over a 7-mile commuting journey you will have very little spare heat to play with. You can barely heat up an engine to normal operating temp in that time, let alone a gearbox as well. I'm running a diesel, and diesels are much less inefficient at lower engine temps than petrol engines (as far as I understand at least.) If you can't pre-heat the engine, then the priority has surely to be getting that engine up to a good temperature as quickly as possible. I like the idea of THEN using excess engine heat to warm the transmission, but I can't see that happening in 7 miles. Maybe block the radiator grille aggressively, and fit an under-engine fairing if there isn't one already, thereby raising the air temperature in the whole engine bay, ...maybe that would help?