I wanted to replace the radiator hoses in my '08 with the 2.2, so this would be a good time to install a transmission cooler, too. With the lower hose out of the way I had much better access to the original transmission cooler lines. The cooler I bought was part #91023111 from Speedway Motors, the rubber cooler hose is 8mm, or 5/16". Use trans cooler hose ONLY, do not substitute! I alos bought some radiator cooler line retainer clips, also known as Jesus clips, because once you drop them into the engine you will yell "Jesus!", because you can never find it. Buy at least 5, they are cheap. Also have an assortment of splash pan retainer clips as the inner left piece has to be completely removed. I bought a new cooler line assembly since the original was already 18 years old, GM part #18619-02265338. Also buy a good tubing cutter, you will need it. A hacksaw might work.
The rubber flaps around above radiator and driver's side need to be removed, along with the hood latch. I mounted the cooler on a piece of aluminum flat bar stock from Home Depot and installed it behind the bumper using the 2 bolt studs stick out from the bumper itself. I believe the nuts needed are 8X1.25. In this location there is a gap between the cooler and condensor, which allows for better heat transfer. Some mount the transmission cooler directly on the condensor, I won't do that.
The return line to the transmission is the lower line on the radiator, it must be modified so the new cooler can go in series with the aluminum line. On the new GM line assembly cut out the elbow and extra line required so you can slide the new hose on, just a few inches from where it goes into the radiator. Blow out everything with air before final installation. NOTE- the factory cooler line assembly is difficult to get out and in, note how it is routed- take notes and photos. The splash guard must be removed first, there is a retainer clip near the fog lamp that is difficult to get to, it must come out for removal of the part.
I installed the hose onto the cooler line before installing the cooler line to the transmission and used 2 clamps instead of one. Installing the assembly onto the tranmission while trying to route everything is extremely difficult, be patient. The A/C lines will also be in the way, be careful with those as you don't want to break one! NOTE- have the Jesus clips in place before this proceedure on both the upper and lower radiator connection points. The line fitting just pushes into place on the radiator after the Jesus clip is properly installed, very easy.
When the cooler lines are in place and the 10mm nut is tight it is only a matter of connecting the hoses to the cooler.
Now you can reinstall the lower hose and fill with coolant. The transmission might need a few ounces of fluid to account for the new cooler. To properly burp the cooling system elevate the front of the car after it has reached operating temp and cooled down. Air will rise to the cap and you can fill. Do this at least twice, and verify the tranmission level as correct. This is done with the engine running, replace the plug while the engine is still running (11mm wrench) or you will lose a lot of fluid with the engine off.
Installing the cooler and modified lines is a difficult task, not for the faint of heart. There isn't much room to work and nothing goes back together without thought and effort. You must have a lift, doing this with a floor jack will only double the difficulty. I have a QuickJack, which is good because the car must be raised and lowered several times during the job.




The cooler mounted on the aluminum flat bar. The holes have to be elongated slightly because the bolts on the bumper are not parallel.


The cooler in place before it was connected to the transmission.




The old and new GM cooler lines before modification. The shorter line must be cut to allow the hoses to be installed. The part that goes into the radiator will be a short stub with a 90. Use 2 clamps on each hose.


Cut the return line pipe where you see the 2 black lines. The new cooler is plumbed in between these 2 points. The stub goes into the lower radiator port.


This is what the stub should look like after the cuts.




The modified cooler assembly in place. One hose is connected, the upper one isn't. Note the 2 clamps. The A/C pipe leaves little clearance! Have the Jesus clips in place before installing the lines into the transmission. Then push into place, slide the dust guard over the connections.


Here's the view from above. See the ground connection on the engine block? Now is the time to clean that connection if you live in a corrosive enviorment and prevent future electrical problems. Disconnect the battery ground first!


This is the new cooler in place. Note how the hose clamps are staggered, they do no have to be doubled here.


This is a Jesus clip, and holds the cooler line into the radiator. Have extra on hand, you will lose at least 1.


Use oil cooler hose ONLY! I bought mine online, local parts store didn't have it.

 

Nice write up and how to! Thanks for the photos to show how you did the work!

 

A couple of questions.

Is the new cooler in line with the radiator cooler? if so, is it before or after and why?

I assume you cut the radiator fitting just before where the old hose connected. did you consider cutting the crimped ferrule to see if you could get the hose off and find out if the tube had a bead on it so that the new hose couldn't fall off? Doesn't seem like double hose clamps makes up for a missing bead.

 

The cooler is parallel to the radiator/condensor in front of the condensor, behind the bumper. in this position it would not block air flow to the condensor or radiator, but still get enough air to function properly.
I wanted both original rubber hoses kept in place with the replacement GM cooler line assembly because the clip between the 2 lines would function to hold both in place. I left the maximum amount of aluminum line so the hose to the new cooler could be double clamped. Both cuts had to be made right at an elbow so there was enough pipe to clamp to. The cooler line hoses will not come off using 2 clamps. With my last HHR I had a very similar installation and the hoses never came loose in 15 years. The transmission shifted normally at 200,000 miles, too.


This is a better view of how the cooler is mounted.

 

This should probably go to either "drivetrain" or "how-to".

 

Moved to drivetrain and made it a sticky!

 

You didn't answer one of my questions, How does the transmission fluid flow?
Transmission to new cooler and back
Transmission to new cooler, then radiator cooler, then back
Transmission to radiator cooler, then new cooler, then back

There is a tool called a bead rolling tool or beading tool, something like one of these:

Earls Bead roller

Or of you're lucky maybe you find one of these in a thrift shop:

Parker Appliance Beading Tool

Then you can be sure the hose will never come off. The Parker set is mine, picked up at Earls Supply many years ago for $35 or so.

 

Hot fluid leaves the transmission and travels to the radiator via the upper cooler line. The fluid is 'cooled' by the radiator and exits at the bottom, then enters one of the rubber hoses to the new cooler. After it exits the cooler it returns to the transmission via the other rubber hose and then a section of the GM cooler line assembly. This is the lower inlet on the transmission, the lines are vertical at the transmission case.
The new cooler is placed in series with the return line to the transmission. You need to cool fluid AFTER it leaves the radiator, not before it enters.
A bead could be added, but clamps are sufficient to hold the hose in place. I drove an '07 for 15 years like this with no problems. HOWEVER, a bead would be a good addition, I agree with your suggestion.