transmission bypass filter not heating up

[mjo]

Hi Everyone,

The previous transmission setup that I had teed off of the transmission oil temp sensor, had a restrictor orifice and returned the cleaned oil to the (top) pan. Hoping to reduce the number of fittings, remove the very small restrictor that could plug up, and add in a few hydraulic quick-disconnect couplings I changed it to run parallel to the trans cooler. The trans cooler that I have is an independent aftermarket one - I'm not using the heat exchanger built into the rad. There is also a thermostat installed between the trans and the cooler to help facilitate torque converter lockup during the upcoming cold Michigan weather. So after having the three components installed - bypass filter, thermostat, and trans cooler all in parallel - and doing a 20 mile drive, the bypass filter didn't heat up. However, the thermostat was quite warm to the touch. Thought it was maybe air in the lines not being able to pass through the saturated TP roll so I installed a fresh roll. That didn't help. I'm wondering if I should put a flow restrictor in there in either the inlet or the outlet before the filter? I found a check valve with 2 psi cracking pressure ($22). What do you think? I appreciate any suggestions - thanks.

 

[Tempest]

That sounds like a lot of work and fitting when you could just run a fine hydraulic filter as a full flow.

 

[handyman]

Is the filter before or after your thermostat?

 

[Gary Allan]

Do you still have the restrictor in the MG/Frantz? If so, ditch it. You are probably running an easier short circuit with the thermostat. Depending on who makes it, they don't close all the way on the COLD bypass route. Perma-Cool works this way. (They say) 10% still bypasses the cooler as a fail safe. I don't know how they get 10% since it's going to be altered by visc and the distance/resistance of the cooler

If you still have your same radiator, hook its inlet to your COLD OUTLET of your thermostat. Plug the HOT INLET of your thermostat and Tee the returns of BOTH to the trans. You'll then modulate between the in rad and the auxiliary depending on trans temp ..and will create enough static pressure drop across the circuit to drive your bypass filter.

Essentially you're using the thermostat as a diverter or an "OR gate" for those of Boolean persuasion.

 

[mjo]

Yes, the bypass filter is before the thermostat which is before the cooler.

Also the 1/32" restrictor was removed.

 

[Gary Allan]

The check valve would not be a bad way to handle this if you're opposed to putting a little more static resistance in the circuit. I don't use a thermostat and run my OEM and auxiliary coolers in series.

I've had no problem getting my BP80A w/BP90 filter warm doing it that way ..but it's more easy to see why.

 

[mjo]

Thanks Gary.

Would 5 PSID be too much to put on the cooling circuit? I have no idea how the automatic hydraulic circuit is hooked up - where the fluid originates from and if this pressure difference would affect shifting. For example, what if I put in a check valve with 5 PSID cracking pressure and the cooling lines are supplied by a pressure source of 5 PSID? Then nothing will flow through the cooler. But if it's directly tied to the pump then maybe it doesn't matter?

The hydraulic couplings were warm to the touch. They are large so perhaps they are acting as a heatsink. Perhaps I'm thinking about this too much.

It's probably time to buy the FSM for the trans or get a BSME.

 

[mjo]

Quote:

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That sounds like a lot of work and fitting when you could just run a fine hydraulic filter as a full flow.

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It was fun tinkering around with hoses and the benefits of TP filtration are worth it IMO.

 

[Gary Allan]

What's this on, mjo? Most cooling circuits that I'm aware of aren't regulated. Apparently BIG FORD autos have a relief valve that bypasses the cooler circuit when cold (a sprung ballort) ..but most merely modify the shift pressures and don't alter the flow.

All that I've encountered are relatively low pressure circuits ..but that's due to no restrictions. That is, they'll reach higher pressures up to the limits of the pump ..just like an engine.

No worries as far as I'm concerned with 2, 5, or 25 (watch someone point out some installation where .0002" of water column makes a big difference

)
As far as ff vs. MG/tp/bypass ..I like both. The bypass does such a fine job ..but the full flow would offer more protection from stray debris from the converter. Not that it's common these days.

 

[mjo]

Gary, this is on a fuel-sipping '95 Saturn SL2. The TAAT on the saturn has a spin-on full flow from the factory. Despite the FF the transmission is known to fail it's solenoids which then causes harsh shifts. The bypass cleans out the oil and makes it shift great!

Great to hear that the check valve would probably work. If I could find a flow spec for the cooling circuit I could look up a suitable restrictor that could add 2-5 PSI to the bypass filter. The restrictor would weigh a lot less than the valve.

 

[Gary Allan]

I keep trying to find something like an air line regulator ..but in a 3-way. They just don't seem to be available compact and cheap. The preloaded check valve seems to be the best alternative.

The check valve will definitely work. Your bypass filter will see a constant 2 or 5 psi (whatever you spec it for). Schultz turned me on to this when we were pondering this endlessly. His ran a bit more than your source ..but it was some time ago. The end user price after S&H was about $40. Not bad for a one time fee for a needed component ..but if you're constantly tinkering with stuff like this, you tend to get a little tired of spending too many $$$ for not enough utility.

 

[Tempest]

Quote:

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It was fun tinkering around with hoses and the benefits of TP filtration are worth it IMO.

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You and Gary will get along swell.

Do carry on!

 

[mjo]

I checked the bypass filter a few days after installation and it wasn't hot after I drove it. A week after the installation it got warm to the touch. I figure that if it takes that long for the BP filter to fill up there definitely isn't enough flow diverted to the filter. So I decided to add the check valve with a 5 PSI cracking pressure between the inlet of the filter and the thermostat.

After driving it around for 15 miles the filter gets very hot but the thermostat is now room temperature

. Is all of the flow now being sent to the bypass filter? I made sure that the arrow on the check valve was pointed in the direction of flow. Anyway I'll give it a couple days then add the restrictor back on the outlet side of the filter to see if that fixes the problem.

 

[Gary Allan]

Hey, pal ..join the club of system tweakers.

You'll get it just right sooner or later.

 

[mjo]

Here's an update on the bypass filter. Good news - I found out that there's actually plenty of fluid flowing into the cooler!

One of the cooler lines became loose at my aftermarket trans cooler while I was driving and squirted fluid everywhere. It leaked at a point after the check valve - which means that it didn't leak because of the cracking pressure (5 PSID) of the check valve. Had to tow a few miles but my car is back in operation. Thanks for the help, Gary!

 

[Gary Allan]

Ouch! All's well that end's well.