The Throttle Body (TB) coolant bypass modification is pretty easy and already well documented for models up to 2012. I'm just adding to that with a DIY specifically on the 2013 3.8 (maybe 2.0t as well) since it is a little different with the coolant lines on the bottom, requiring extra work to get to them.
The benefit of this modification is to prevent unnecessarily heating the TB and the air passing through it with 175+deg F. coolant. Heating the TB is only necessary in some extremely cold and damp conditions where the throttle plate could freeze up the during a cold start.
This modification is obviously beneficial in theory, but I'm skeptical whether it makes a measurable difference. Anyone with phenolic or thermal gaskets for the TB or surge tank might be more likely to see improvement.
Here's what you'll needed:
Roughly 30 minutes with a cold engine
Phillips #2 screwdriver
Small flat edge screwdriver (optional)
Long nose pliers (optional)
1 foot of 5/16" radiator or fuel line hose (<$2)
Heat gun or hair dryer (optional)
Shop wrag or paper towel (optional)
The first part and most of the work is just getting everything out of the way so you can get to the coolant lines on the bottom of the TB. This first section mostly applies to those with the stock airbox.
Disconnect the wire anchor that's attaching the sensor wire to the airbox. Do this by pinching one side of the arrow headed anchor part. A small screwdriver makes this easier:
Unplug the sensor wires and move them out of the way:
Unclip the top of the airbox:
Loosen the hose on he right side of the TB. Use pliers and squeeze the tabs and move the clamp away from the end. There's no need to disconnect it. It just needs to swivel:
Unscrew the clamp on the hose to the left of TB. Again, you only need it to swivel, so just unscrew it until it feels loose:
Loosen the main hose clamp attaching the airbox to the TB. Just unscrew it until there are only a couple gear slots left on the clamp:
Pull the main piece back a half inch from the TB or until it's no longer connected:
With the main hose disconnected and the other two able to swivel, you can lift the top of the airbox up and flip it back so that it lays upside down behind the TB and out of the way:
Now you can finally get to the coolant lines. The rest of this will apply with or without the stock airbox. You should see two lines going to the TB. One is feeding coolant in and the other is returning it back to the coolant system. These two hoses neeed to be removed.
The first step is to squeeze the tabs on all four clamps and slide them toward the middle of the hoses. In this picture you can see one clamp (in the bottom left of the pic) already moved. Long nose pliers make this job a little easier:
Once you have moved all the clamps you can remove the hoses by pulling and twisting them off of the steel connectors. If they won't budge, just warm them up with a heat gun and they will come right off. You should expect a very small amount of coolant to leak out, so put a wrag underneath to catch it.
Use the old hoses to measure a new cut of hose that's 1-2 inches longer that the original ones. You may want to keep the old ones to re-use if you decide to reverse this for very cold climates. Since there isn't much room under there, the original ones that were cut to length may be best. Here's the hose I used for the net step:
The final step is to slide two clamps toward the middle of each of the new hoses and make a closed loop by connecting the coolant feed line to the return line and by connecting the two lines on the TB together. Here's what the end result should look like:
Connecting the two lines on the TB isn't really necessary, but it will keep anything from crawling up in there and from getting any foreign material into the coolant system if you ever reverse this. Here's the final result from another angle:
Lastly, you need to reverse the steps in the first section to put everything back together.
That hose is filtered air that is pulled in by the vacuum from the intake sucking out the PCV valve. On a naturally aspirated engine the flow is 99% in the direction to the engine. Only at WOT and high rpms will it reverse. A turbo will reverse whenever in boost though.
I’ve attempted this mod and currently have an issue with coolant leaking out of the return line.. I have the hose clamped down but I am still leaking coolant. Any ideas? The car isn’t drivable in this condition, as I do not want to overheat my motor
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Disclaimer: As always, I hold no responsibility for damage to your vehicle or injury to your person while attempting this modification.
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