I had transmission fluid show up in the engine coolant reservoir of my 1999
Chevy Tahoe. I first noticed this sometime after also noticing an
intermittent rattling (washboarding) which sounded like it was coming from
the transmission. I made the mistake of continuing to drive, and about 25
miles later the entire transmission went out (only neutral "worked"). (BTW,
the vehicle has TWO auxiliary transmission coolers in series with the cooler
in the radiator.)
Different shops give me different explanations as to what happened. I'd
like to get YOUR experiences/opinions!
Theory 1: The transmission was failing (possibly torque converter going
bad), causing bits of metal particles and debris to plug the transmission
cooler part of the radiator, which caused fluid to spill into the overflow
reservoir (just how I don't know).
Theory 2: The transmission cooler in the main radiator developed a leak and
allowed fluid to leak into the coolant and coolant to leak into the fluid.
The coolant, once getting inside the transmission, ruined it.
Theory 3: ???
At any rate, when the transmission got rebuilt the shop also bypassed the
main transmission cooler so that I am now using only the two auxiliary
coolers. I am posting separately with questions about this.
I'd like to get your opinion on which theory above is most likely, but my
main question is: If only the transmission cooler in the main radiator
developed a leak and not the engine coolant part, then how can the
transmission fluid get mixed in with the coolant? (It *did* happen -- I'm
just trying to understand *how* it was possible.)
# 2, possibly aggravated by the internal cooler plugging up with
debris........pressure in the cooler circuit will rise to line pressure (up
to a couple hundred pounds) if the cooler is plugged; up to the point at
which it is stopped up
Basic concept at work in this one: "If you can't dazzle 'em with
brilliance, baffle 'em with bullshit." Although your TC *MAY* have been
chewing itself to pieces, which *MAY* have been forming a blockage in
the tranny-cooler section of the plumbing, there's no possible way (As
in none, zero, zip, nada, zilch) for transmission fluid to "spill over
into the overflow reservoir". Somebody was feeding you a line of shit in
an attempt to appear wise, when in actuality, they were clueless, and
hoping you were too.
*MUCH* more likely. A hole in the loop that goes into the radiator would
allow exactly this sort of thing to happen.
There is no theory #3. Theory #4: NO POOFTERS! Oh, wait... wrong skit!
So sorry, old bean! :)
Probably because they figured out that there was a leak in the
transmission cooler section of the radiator. Hopefully, they also sealed
the in/out from the tranny at the point where it enters/exits the
radiator when they did the bypass. If not, you're in for coolant
leakage. Exactly how much/how bad isn't predictable from the information
I've seen you give so far, but there will be leakage.
The tranny-cooler part of the circuit is usually (I'm sure there are
exceptions, and I'm just as sure somebody will point to them in an
attempt to "prove" me wrong) just a loop of tubing inside the radiator
that the coolant flows around. There is no "separate compartment" or
whatever that deals strictly with the tranny fluid. The loop is simply
run into the radiator, and sits there submerged in the coolant that's
normally present. No "magic" going on - It's just "Dump the heat from
the tranny juice into the water in the radiator, then let the radiator
worry about dealing with it."
A hole in the loop, whether from rust, mechanical trauma, or whatever
other source lets tranny juice out, and water in. The result is (sooner
or later) a dead tanny and a cooling system with transmission fluid
Don Bruder - email@example.com <--- Preferred Email - SpamAssassinated.
Hate SPAM? See <http://www.spamassassin.org for some seriously great info.
Did they plug the transmission cooler lines coming from the radiator? If not,
there has to be coolant running out the tubes OR there is nothing wrong with
In any event, in cold weather the transmission fluid needs to go through the
lines in the radiator to warn it, so I'd have a radiator shop clean and test
it for leaks for peace of mind.
|> At any rate, when the transmission got rebuilt the shop also bypassed the|> main transmission cooler so that I am now using only the two auxiliary|> coolers. I am posting separately with questions about this.
|Did they plug the transmission cooler lines coming from the radiator? If not,
|there has to be coolant running out the tubes OR there is nothing wrong with
|In any event, in cold weather the transmission fluid needs to go through the
|lines in the radiator to warn it, so I'd have a radiator shop clean and test
|it for leaks for peace of mind.
If you do not replace the radiator and restore the radiator loop to the
transmission cooling circuit, you might consider moving the auzillary coolers
behind the radiator, near the top if there is room. That will impart some heat
to the trans coolers in cold weather.
Rex in Fort Worth
Why, praytel, does the ATF need to be heated by the coolant? The ATF heats
itself (that's the reason why you have ATF coolers). All the coolant does
is keep it at 195* after the truck's all warmed up.
Cold fluids not as efficent as warm fluid, too thick, and in sub zero temps,
it can pay to have the engine run for a while heating the fliud for a few
minutes before putting the auto in gear and moving off.
Totally unessesary in Florida, but can be vital in Alaska.
at least thats my understanding from lurking around elsewhere.
Actually, the coolant isn't 195F by the time it gets to the ATF cooler
in the bottom of the radiator, even though it entered the top of the
radiator at that temperature. Wouldn't be a very good radiator if it
didn't cool the coolant!
!Replace DECIMAL.POINT in my e-mail address with just a . to reply
Others have already given you the answer, but if transmissions didn't need
that liquid to liquid heat transfer, maybe you can explain why all automatic
trans equipped vehicles come equipped from the factory that way
who is not trying to reinvent the wheel!!
All automatic trans equipped vehicles *don't* come from the factory
that way. My '99 V10 has no connection to the rad . . . just a cooler.
I would presume that if cold transmissions were a problem, they they
would need new trannies every year in Alaska where the average tranny
temp never even gets above 0F when the ambient temps are hanging
if the in-radiator cooler is SO necessary, perhap someone can explain why
I've not had a problem with totally bypassing it in EVERY truck (and a lot
of cars) in which I've overhauled the transmission SINCE 1997.
the VERY FIRST ONE, an F-350 7.3 PSD (Turbo) has over 330k on the overhaul,
with only two fluid changes (hey, the owner 'doesn't have time' to have it
done), and is still going strong, hauling a 30-foot stock trailer all over
the country. This was equipped with a pair of Hayden 1679's, the big
mothers, plumbed in series.
I really have to wonder about that. How cold are you talking?
10C? 0C? -20C? -40C?
You can warm the fluid in the transmission easily. Put it in drive and
keep foot on the brakes. The torque converter is turn horsepower into
heat and that's circulating through the fluid...
A host is a host from coast to firstname.lastname@example.org
& no one will talk to a host that's close........[v].(301) 56-LINUX
have the radiator shop pull the radiator and replace the trans cooler
that is made as part of the radiator...
sorry about the mixup
On Tue, 21 Oct 2003 16:35:57 -0500, Elbert Clarke
Perhaps a bit of a sidebar to this:
At some point in the past couple of years, Monaco moved to an aluminum
radiator. There have been numerous failures of the internal
transmission cooler, with subsequent transmission failures. The story
as I've been told is that it is an electolysis problem with different
In any case, a full recall affecting hundreds of vehicles was issued.
Fix was a kit to mount a separate auxiliary cooler and cap off the
I received my recall notice about two weeks after I had the kit
installed; I saw one on an unsold-but-built-later version of my '03
Safari, and since I was having transmission overheating problems I
called to see about getting one. They didn't mention the failure
problem to me, but were very quick to get me a kit and pay for the
install. Overheating problems are very much gone, and it does take a
long time to get very warm. Fortunately I don't do much (any if I can
help it) cold weather travel, but from other posts here it sounds like
there may be a different problem for Monaco when the cold weather hits
One guy who I talked to who got the recall notice 9 days after his
transmission had failed said Pacific Detroit Allison told him they had
replaced 450 (with rebuilds) so far.
A friend in Texas had that experience with his Monaco. His first trip
was trouble free-- the next 3 were disasters and he got towed in. As of
the first year Monaco has spent $30,000+ rehabbing his new coach. He
took it to Monaco factory in August, haven't learned what all his
results were but I know he spent a week at the factory. This was AFTER
he had the engine and transmission replaced.
Your second theory is correct. The factory cooler is located inside
the radiator tank, physically surrounded by coolant. When it leaks,
coolant gets in the trans, and ATF in the coolant. Not uncommon at
The Engine radiator is a Air to Liquid heat exchanger. The
transmission cooler is a liquid to liquid cooler. The transmission
cooler is located inside the "return" tank of the radiator. This water
has already been cooled by the radiator and is on its way back to the
engine. The engine coolant at this point is cooler than the ATF, so
the coolant removes heat from the ATF.
Most US vehicles have the automatic trans fluid running through the radiator
I would buy a new radiator and get the line hooked back up to it.
I would have your transmission serviced every 50,000 miles. maybe 30,000
with lots of towing?
I hear of lots of GM vehicles loosing their auto trans before 100,000 miles.
After a good rebuild at a good trans shop they seem to run much longer?
Many large Ford, GM and Dodge trucks are all coming with beefier
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