Category Archives: Transmission Oil Cooler

Condensers with Integrated Transmission Coolers

Have you encountered a condenser that was leaking transmission oil?  If not, you will, as integrated heat exchangers are becoming more and more common in both passenger and light truck applications.

The most common transmission oil coolers are oil to water heat exchangers located in the outlet tank of the radiator.  When the capacity of an in-tank coolers does not meet the transmission cooling requirements then an auxiliary cooler may be added to the layout.  But this arrangement adds complexity and creates assembly and servicing issues.  Both of these conventional arrangements still cover the large majority of current production vehicles.

Over the last decade, engineers at Chrysler, Ford, and some of the import vehicle manufacturers have released several designs which eliminate the oil cooler in the radiator tank and instead integrate the transmission oil cooling and the air conditioning condenser functions into a common heat exchanger.  Sometimes they also integrate the power steering cooler providing three separate circuits in one heat exchanger assembly.  This arrangement is more compact, lighter weight, and lower cost than previous configurations.

Ford Escape Condenser with Integrated Transmission Oil Cooler

Chrysler Minivan Condenser with Integrated Oil Cooler

A few of the integrated designs include a thermostatic or pressure regulated valve to allow cold – high viscosity transmission fluid to by-pass the heat exchanger.  The 2006 Ford Crown Victoria uses one of these valves.

Ford Crown Victoria Condenser with Integrated Oil Cooler

The transmission oil cooler lines may be connected with rubber hoses and clamps, as in the Ford Escape arrangement, but often they use standard quick connect fittings like those used on the Chrysler Minivan. 

There would not be any special service considerations for these integrated oil coolers if not for the fact that the air conditioning system must be evacuated and recharged if the oil cooler fails, or is damaged, and must be replaced.  Shops performing this repair work must therefore have AC certified technicians and refrigerant recovery – recharge equipment.


Oil Cooler Connections – Ford Truck & Cadillac CTS

In our last tech tip article we reviewed the Jiffy-Tite® connector design which General Motors engineers started to use in some applications in 1996.  While most GM vehicles use Jiffy-Tite® connectors today, the exception is on some of the Cadillac platforms.  The 2003 Cadillac CTS introduced a new low profile quick connect which has proved troublesome to many technicians who see it for the first time.  The new quick connect design used on several Cadillac models is similar to that also used on 2003 Ford Explorer and F-150 models.  See photos below for details of the new connector design as applied on some Ford applications.

Ford Oil Cooler Quick connect and Dis-connect tool

Most mechanics use common tools like the one shown in the above photo to separate the Ford connections but because of the tight bend radius on the tube side of the Cadillac oil cooler lines the common disconnect tool will not fit. The tool shown below is designed for applications like the Cadillac CTS.  When a low profile tool is not available the standard tools have to be modified by grinding away a portion of the collar.

Cadillac CTS Oil Cooler Quick Connect and Disconnect Tool

As discussed in the last Tech Tip, the Cadillac application uses an integrated quick connect design to not only make the connection between the oil cooler and the line but also to secure the oil cooler in the radiator tank.  These fittings are not intended to be disturbed once the radiator leaves the factory. 

Cadillac CTS Oil Cooler Quick Connect and Fitting Removed
Loosening the integrated fittings compromises the factory seal between the oil cooler and the radiator tank and the joint cannot be reliably repaired.  If a technician removes the oil cooler fitting from a new radiator in most all cases the radiator must be scrapped.

Oil Cooler Connections – GM Quick Connects

In our first two tech tip articles we reviewed radiator cap functions and application considerations.  The next few articles will cover the different types of “Quick Connects” used by original equipment manufacturers to attach transmission and engine oil cooler lines to the heat exchangers in the power train cooling system.  In this particular article we will review the Jiffy-Tite® connector design which General Motors engineers started to use in some applications in 1996.  Most GM vehicles use Jiffy-Tite® connectors today, the exception being some of the Cadillac platforms.

Until the middle 90’s most oil coolers were connected to the oil lines using rubber hose and clamp or inverted flare joint designs.  See photo of rubber hose type connection and sketch of inverted flare joint below.

Rubber hose and clamp fitting  

Inverted flare connetion 


Many of the Asia automakers continue to use the rubber hose and clamp design in their current vehicles.  Each of these conventional joint designs has their own merits and disadvantages.  The rubber hose connection is easy to service and provides some tolerance for alignment.  One disadvantage is that sealing is affected by changes in clamping force as the rubber hardness varies with temperature and takes a compression set with age.

Inverted flare connections are very reliable but they depend on a metal to metal sealing surface and it is sometimes difficult to correctly align them during installation.  To seal effectively, one or both sides of the joint surface must be forced to conform to the other as the joint is tightened.  As parts become contaminated with corrosion and dirt it becomes even more difficult to effect leak proof connections. 

In many applications, steel lines and fittings are being jointed to brass or aluminum oil coolers.  When leaks occur at these joints the first repair attempt often results in over-tightening and stripping of the threads on the oil cooler connector.  Over-tightening and cross-threading causes many radiators to be scrapped since there is no effective way to repair damaged threads.  Over-tightening can also cause damage to the oil cooler inside the radiator tank where a leak will lead to mixing of oil and coolant.

Some aftermarket suppliers supply small o-rings to place in the interface between the male and female connections.  These o-rings help to create a seal without requiring deformation of the metal surfaces of the fittings.  See sketch below.

Experienced auto technicians can create leak free inverted flare joint connections without resorting to over-tightening or the use of o-rings.  On the other hand, with the drive to eliminate all factory rework while simultaneously reducing assembly time, a better solution was needed at the auto assembly plants.  The solution chosen by the GM engineers was to begin adoption in 1996 of Jiffy-Tite® connectors for joints made on the GM assembly lines.  Except for a few applications which use radiators and oil coolers produced by Denso, the Jiffy-Tite® connector has become a standard in GM applications and is also used in many Mercedes, Chrysler, and other applications.

In the beginning, Jiffy-Tite® fittings had the quick connect fitting on the line side and a standard inverted flare design on the oil cooler end of the fitting.  Subsequent designs use o-ring or seal washer designs on the oil cooler side.  See photos below.

In many later model radiator applications an integrated Jiffy-Tite® design is used to not only make the connection between the oil cooler and the line but also to secure the oil cooler in the radiator tank.  It is these later designs that prove most troublesome in the field.  These fittings are not intended to be disturbed once the radiator leaves the factory.  Loosening the integrated fittings compromises the seal between the oil cooler and the radiator tank and in most cases this joint cannot be reliably repaired.  See photos below.


To remove the oil line from a Jiffy-Tite® connector first slide back the plastic cover (if present) and then use the appropriate tool to open the legs of the retaining clips.  Once the legs are open the line may be pulled out of the fitting.  If a tool is not available to open the legs then a small screwdriver can be used to completely remove the clip from the fitting.  See photos below.

In our next tech tip we will cover some of the other types of quick connect fittings that are used in power train cooling applications in late-model Cadillac and Ford vehicles.