Trans Cooler Question

[Highway Q45]

I will be installing a B&M cooler soon and still have a few questions.

1. In a mild to hot climate like Sacramento should the existing cooling loop through the radiator be eliminated or paralleled into the new cooler?

2. Will the existing OEM cooler add heat on hot days with high AC loads; or will the Aux cooler impede adequate heat rise in the AT loop on cold days?

3. Would it make any difference to valve off the old unit and switch it in during cold weather if necessary?

I've researched this awhile and DougQ45 has been a big help with old Yahoo threads. Opinions seem to go both ways without any real preference. It seldom freezes here, but gets Africa hot in Summer, I'll use Mobil 1 ATF, and I know my wife doesn't probably warm it up much on cold mornings either. Any Thoughts?

Steve

[maxnix]

I will be installing a B&M cooler soon and still have a few questions.

1. In a mild to hot climate like Sacramento should the existing cooling loop through the radiator be eliminated or paralleled into the new cooler?

2. Will the existing OEM cooler add heat on hot days with high AC loads; or will the Aux cooler impede adequate heat rise in the AT loop on cold days?

3. Would it make any difference to valve off the old unit and switch it in during cold weather if necessary?

I've researched this awhile and DougQ45 has been a big help with old Yahoo threads. Opinions seem to go both ways without any real preference. It seldom freezes here, but gets Africa hot in Summer, I'll use Mobil 1 ATF, and I know my wife doesn't probably warm it up much on cold mornings either. Any Thoughts?

Steve

1.) Eliminated until you move to MN or Manitoba.

2.) OEM heat exchanger is on either end of radiator core, so not using it has no effect on other heat exchanger cores. This is true of later (1994-1996) Q45s. The earlier ones had a different arrangement.

3.) Not unless it is extremely cold, or you can't start the car 5 minutes before your wife leaves.

[paintwgn]

91QI plan to install a ATF cooler soon myself and have the same questions. After reading the various threads and talking with a former Infiniti master tech, I'm going to eliminate the loop through the radiator. In the tech's opinion its better to install the largest B&M or Hayden cooler that will fit and bypass the radiator loop. He mentioned that the OEM radiator loop can become obstructed and partially clogged. The existing heat exchanger won't help to warm the ATF on extremely cold days anyway since the coolant doesn't flow from the block until the thermostst begins to open. My vote is to eliminate the factory heat exchanger. If you decide to connect the cooler in series, consider installing it downstream of the radiator.

[szh]

I will be installing a B&M cooler soon and still have a few questions.

1. In a mild to hot climate like Sacramento should the existing cooling loop through the radiator be eliminated or paralleled into the new cooler?

Steve

The consensus seems to be "eliminate" for the climates we have here in California. The only other commment I might make is that "paralleled" does not make too much sense to me - you do not want the fluid splitting two ways, I would think. My dealer who did the install on the external cooler wanted to put it in series with the radiator (as is normal without the external cooler), but I decided not to - based on feedback from people here.

Z

[DAEDALUS]

How do you know what the overall cooling efficiency is of both systems? There's no question that, on an areal basis, the stock cooler has more cooling area than the aftermarket cooler. Without running any tests, I think the only thing you can almost guarantee by taking the ATF out of the exchanger is that the coolant will run cooler under load. However, I would have to see a thermometer comparison to be convinced that your ATF is running cooler too. The data might exist; I just haven't seen it. By running the external cooler in series, you increase cooling area of the entire system which, reasonably, helps both fluids to run cooler. An in-line cooler may or may not be better than a single external cooler, but it's more of a sure thing.

[sultan]

i put the big b&m, the 70264, not the 70268 others have used. i put it in series after the in-rad, i routed the hoses so that the fluid goes it's normal way and then all the fluid goes through the b&m and then returns to transmission, but i had to use extra fittings to do it (T fittings). I also put mine in front of the rad and ac condensor, instead of between. wouldn't having both connected also increase the capacity, making it better to have it that way?

[AZhitman]

Ditto everything Sultan said - I ran the big 11x11 cooler in series AFTER the radiator and in front of the radiator and condenser. Extra fittings were $3.75.

Dealership says my install is the cleanest they've seen.

[Highway Q45]

Good info! I assume the OEM cooler is somewhat restrictive due to tubing size and design. I would think if run in series with the new B&M the same condition would still exist and fluid return rates would be reduced compared to B&M only. If the Aux cooler was run in parallel it would act more supplemental without the restriction. The question is does it add or reduce heat? Not having any experience I would say it wouldn't do any harm. Or maybe I have that backwards!!!!

[Q45tech]

Just remember the radiator is working to keep the coolant at 176-180F but the input temp may go to 220-230F in Summer so the cooler end of the radiator is still running around 200F..........how can the oem in radiator heat exchanger COOL the ATF below its own temperature~~~~~200F.

The [ac heated] air flowing thru the external cooler will be under 140F [even in 100F ambient traffic] so assumming the new cooler is large enough it should drop the heated ATF to at least 170F flowing back to the transmission.

Obviously if it is 30F ambient [in winter] the ATF will be cooled to maybe 50-60F by an external cooler..........the AT has a temperature sensor to adjust the line pressure to accomodate cold ATF [thicker more viscous].

The Mobil Syn ATF has more uniform molecules as such it is thinner cold and thicker hot [at extremes] - yet meets the 32F/212F specifications of Dexron IIIg.

You can't go fooling the AT too much as the temperature sensor [TCU] expects a certain viscousity for a certain temperature reading.......why you have trouble with THICKER HIGH TEMP or RACING ATF..[even expensive synthetics]........the pressure gets out of whack expecting a thin ATF.....rough slam engagements.

The worst conditions for an external cooler is stuck in traffic with little air flow AC on and lots of stop and go accelerations.But the in rad exchanger is worse because the temp may creep up to 220F and the air flow thru the external never gets that hot----always cooler.

[szh]

How do you know what the overall cooling efficiency is of both systems? There's no question that, on an areal basis, the stock cooler has more cooling area than the aftermarket cooler. Without running any tests, I think the only thing you can almost guarantee by taking the ATF out of the exchanger is that the coolant will run cooler under load. However, I would have to see a thermometer comparison to be convinced that your ATF is running cooler too. The data might exist; I just haven't seen it. By running the external cooler in series, you increase cooling area of the entire system which, reasonably, helps both fluids to run cooler. An in-line cooler may or may not be better than a single external cooler, but it's more of a sure thing.

Hi, Daedalus!

I see where you are coming from, but I was under the impression that the main radiator stays pretty hot in hot climates due to its cooling the engine coolant fluids. So, it is not going to cool the transmission fluid down to where it needs to be for optimum use in hot weather (i.e., where the low temp of coolant coming out of the radiator is hotter than the normal high temp for the ATF).

That argument on previous posts is what led me to take the radiator out of the picture for my installation! Was I wrong?

Z

[szh]

Just remember the radiator is working to keep the coolant at 176-180F but the input temp may go to 220-230F in Summer so the cooler end of the radiator is still running around 200F..........how can the oem in radiator heat exchanger COOL the ATF below its own temperature~~~~~200F.

Oh ... er . I posted my response/question to Daedalus before reaching the end of the posts and just saw your post. You have factualized it much better than my post. I interpret from your comments that you are in favor of using the external cooler only, right?

Z

[Highway Q45]

Thanks Dennis,That was just the info I needed. Do you think the Aux cooler would still produce similar results if located in the Active Suspension area of the wheelwell or does the fan induced airflow of a grill mounted Aux produce the best drop in ATF temp? It would seem that the wheelwell mounting would also allow better cooling for both the AC and engine by not impeding air flow in heavy Summer AC/traffic load conditions. I guess I'll eventually be leaving the in-rad cooler out of the loop but might hook it up first in series and then in parallel for jollies. I'll try to take my Fluke/IR sensor and get some readings with different cooling circuits. One thing we all agree on is doing nothing isn't an option. Thanks to all for your input, this Forum is just the BEST!

Steve

[szh]

Hi, Steve.

I would be tempted to put it where the recommendation seems to have been in previous posts - "near" the existing radiator. If only because in real cold weather (when you drive from Sacramento to Tahoe, for example! ), you might want some of the heating effect from the radiator. To prevent the ATF from getting too cold that is.

Having installed a B&M in my 1995 Q, and replaced the transmssion at the same time due to previous problems, I can say that I have not had any problems since then - almost 10k miles. "Touch wood "(knocking on top of head).

Frontier Infiniti in San Jose did all the work and they decided to honor the 12k mile warranty (which I have not had to use) even though I made them leave the radiator out of the ATF cooling loop and also use Mobil 1 Synth ATF rather than the Nissan ATF that the reman transmission came loaded with.

Z

[Highway Q45]

Thanks Z,

Did you mount your cooler behind or infront of the AC condenser? AZ and Sutan; with your coolers upstream of the AC, did you notice any effects on AC efficiency on really hot days? I know that the only time I've felt my transmission really slipping was in very slow traffic on a hot day last Summer in the hilly sections of San Francisco. Nothing like sitting in stalled traffic pointing uphill to really heat the Q up. I doubt I'd ever take it to Tahoe in the winter anyway; it's tail-happy enough in the rain...snow would be a real thriller! I will try to get some temps though, it would interesting to see if we are just splitting hairs here. Thanks

[PalmerWMD]

In summary:

The most common cooler install is this:

between radiator and AC condensor, completly bypassinbg the stock heat exchanger.This is also the set-up that some better shops will install automatically unlesss told otherwise.

However, on the Q 45 there is that actsus cooler location (on non actsus cars) which some members have also used successfully but it neccessitated a smaller cooler to fit there.

Fred..

[reggiegsd]

Hey Dennis,

Did you ever find the specs for your aluminum radiator?

The make it better urge is flaring up again.

[szh]

Thanks Z,

Did you mount your cooler behind or infront of the AC condenser?

I did pretty much what Fred said in his post here! Including bypassing the radiator entirely.

Z

[DougQ45]

Greetings Steve: I'm telling ya!!!!! Pull the radiator and have it cleaned at a shop, then put the B & M just below the horizontal A/C pipe, with the plastic tie straps, and you will be a happy camper.

Hey -finally put your re-built Bose amps in the front left of my 91 and it FIXED MY DEAD SPEAKER! Thanks. Believe it or not, the 90 and 91 are dramatically different!!! thats why it did not work in the 90. Thanks again for your help that day.

P.S. the plenum pull is a real PITA.