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Coolant Expansion Tank Replacement
 
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Pelican Technical Article:

Coolant Expansion Tank Replacement

Jared Fenton

Time:

1 hour1 hr

Tab:

$120

Talent:

**

Tools:

16mm socket with extensions, T30 Torx driver, 12mm triple square socket, pliers, flat head screwdriver, fluid pump and 5 gallon container

Applicable Models:

Porsche 955 Cayenne S (2003-08)
Porsche 955 Cayenne Turbo (2003-08)

Parts Required:

New coolant expansion tank, coolant

Hot Tip:

Work on a cool engine

Performance Gain:

Better cooling

Complementary Modification:

Replace headlight bulbs, replace torque strut

The coolant expansion tank (CET) is one of those items that tends to start failing in cars with higher mileage. The CET has a manufacturing seam that can split due to the constantly changing temperature and pressure conditions inside the cooling system. This usually starts with a coolant level warning. If you get one, take a look around the CET for tell-tale signs of coolant leaking from the seam. If you do find a leaking CET, replace it as soon as possible. The good news is that replacement is easy and should take no more than an hour.

Begin by opening the hood and remove the left side engine cover (see our article on removing engine cover for more information). Remove the cap on the CET and check the fluid level. You'll need to remove any fluid left in the CET prior to removing the tank, otherwise it will just spill out all over the floor when removing the hoses.

The method I like to use is a simple aftermarket electric fuel pump. These are readily available at any good auto parts store for around $20. I connect the pump inlet hose down to a small diameter plastic hose that allows me to slide it inside the CET and get as much coolant out as I can. The outlet of the pump simply feeds into a clean 5 gallon container. The nice thing about this method is that it allows you to simply pour the existing coolant back into the system when you are done.

If your CET has been leaking badly and there is a significant amount of coolant lost from the system, a vacuum bleeder is a must have item. In these cases, air usually gets into the system and there really isn't a way to bleed it out manually. A vacuum bleeder allows you to evacuate all the air from the system using a vacuum. You then use the vacuum inside the cooling system to draw the coolant in. All things being equal, you should have just enough coolant inside the system when the pressure inside the cooling system equalizes. See our article on Coolant Flush and Replacement for more information.

Replacing the CET also involves removing the left side headlight to access a bolt. See our article on Changing Light Bulbs for more information. It also helps to remove the left air filter cover. This provides a bit more clearance when getting the CET out. See our article on Air Filter Replacement for more information.

Shown here is the coolant expansion tank on the Cayenne.
Figure 1

Shown here is the coolant expansion tank on the Cayenne. Begin by opening the cap and checking the coolant level inside. It's a bit difficult to see inside but a good flashlight helps. Any remaining coolant must be removed.

Shown here is a simple aftermarket fuel pump available at most auto parts stores.
Figure 2

Shown here is a simple aftermarket fuel pump available at most auto parts stores. In this case, I have stepped down the lines going to the pump to 1/4" OD plastic tubing. This will allow you to place the tube into the CET to suck out all the coolant. The other end of the tubing goes into a 5 gallon plastic container. I f you plan on re-using the coolant, you can simply pour it back into the CET and top up as needed.

Place the tube down in the CET as far as you can, activate the pump and move the tube around to evacuate as much coolant as possible.
Figure 3

Place the tube down in the CET as far as you can, activate the pump and move the tube around to evacuate as much coolant as possible.

Begin removing the CET by detaching the torque strut from the mounting bracket on the engine.
Figure 4

Begin removing the CET by detaching the torque strut from the mounting bracket on the engine. Hold the bolt on the engine side (yellow arrow) by using a 12mm triple square socket while removing the 16mm nut on the back (green arrow). Once the nut is removed, pull the bolt out from the front.

Now remove the left headlight (see our article on Changing Light Bulbs for more information).
Figure 5

Now remove the left headlight (see our article on Changing Light Bulbs for more information). Inside the fender, you can see the 16mm bolt that holds the torque strut mounting bracket to the chassis. Use a long extension to reach the bolt. You'll also need to pull the end of the washer reservoir fill neck (yellow arrow) straight back towards you, this will detach the filler neck from the tank. Carefully guide the filler neck out from inside the fender. WARNING: Be aware that all of the washer fluid will come gushing out after you remove the washer filler neck--so prepare for it. 

Directly below the CET is the 16mm bolt (green arrow) that secures the torque strut mounting bracket to the body.
Figure 6

Directly below the CET is the 16mm bolt (green arrow) that secures the torque strut mounting bracket to the body. Loosen and remove the bolt. Now carefully remove the whole torque strut assembly out of the engine compartment.

Now remove the T30 Torx screw (green arrow) securing the CET to the body.
Figure 7

Now remove the T30 Torx screw (green arrow) securing the CET to the body.

Use a pair of pliers to loosen and slide back the hose clamp (green arrow) on the water line.
Figure 8

Use a pair of pliers to loosen and slide back the hose clamp (green arrow) on the water line. Once slid back, carefully pull the water hose off the CET. Also press the tab (yellow arrow) on the electrical connector and pull it off the CET.

Carefully pull the water hose off the CET at the front (yellow arrow) and then pull the CET out from the body in order to access the hose clamp (green arrow) holding the other water hose on.
Figure 9

Carefully pull the water hose off the CET at the front (yellow arrow) and then pull the CET out from the body in order to access the hose clamp (green arrow) holding the other water hose on. Once slid back, remove the hose.

Don't forget to pull the grommet molded into the water hose off the CET (green arrow).
Figure 10

Don't forget to pull the grommet molded into the water hose off the CET (green arrow).

The final step is to loosen the hose clamp on the main hose at the bottom of the tank (green arrow).
Figure 11

The final step is to loosen the hose clamp on the main hose at the bottom of the tank (green arrow). Be prepared for some coolant to spill as you pull the hose off. It is helpful too lay down some shop towels directly underneath.

The last step is to carefully maneuver the CET out from the engine compartment.
Figure 12

The last step is to carefully maneuver the CET out from the engine compartment. Take your time as it can be a little tricky to get it out. Installing the new tank is simply the reverse of removal. Don't forget to check the coolant level afterward.

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Comments and Suggestions:
Boa Comments: I just saw a pool under the left front corner in front of the drivers tire, can't see any leaks from above. Thoughts, just dumped out the oil in the turbo hose last week and had the wheel well cover off and did not see any signs of leaks or drips. changed tires two days ago and did not see any signs of drips?
December 3, 2016
JW Comments: Been having some coolant lost issues and found this tech article very helpful. Looks to me like it's the right headlight assembly that gets removed. Also, would like to know the torque to numbers for the larger bolts.
June 16, 2016
  Followup from the Pelican Staff: I don’t have that info.

I would grab a repair manual. It will have the procedure, special tools and torque specs.

Give our parts specialists a call at 1-888-280-7799. - Nick at Pelican Parts
 
BK Comments: Geesh.... Anyone want to buy a 2005 Cayenne S in great condition with 71k on the clock?
March 4, 2016
  Followup from the Pelican Staff: I opened a post in our forums. A Pelican community member may be able to answer your question.
- Nick at Pelican Parts
 
BK Comments: CET = coolant expansion tank= the subject of this link = the same abbreviation the author of this article used as well as the other commenters and responders of the article.

Anyway, the replacement CET I bought blew worse than the first one after 45mins of driving. The force buckled some of the metal surrounding it. What can be the cause? Thermostat maybe?
March 3, 2016
  Followup from the Pelican Staff: I answer a lot of questions, the more clarity the better when asking, it makes responding easier.

Likely too much pressure in the engine. I would check for a faulty cap and for combustion gases in the cooling system. You may have a faulty head gasket. - Nick at Pelican Parts
 
BK Comments: Replaced CET.. No heat blowing from the vents even when the temp on the unit is on HIGH
February 15, 2016
  Followup from the Pelican Staff: What is a CET? it helps if you spell out abbreviations. - Nick at Pelican Parts  
Ken Comments: I have this odd sympthom when the car is left for a couple of days. The coolant level warning comes up but goes away after the car is runing for a while.

Is it possible to remove the level sensor to clean or is it molded onto the tank?
November 27, 2015
  Followup from the Pelican Staff: It's probably not the sensor. The coolant level maybe low, rising to the correct level once warm. - Nick at Pelican Parts  
Mark Comments: i did all of the above steps to remove and refit the CET tank.
checked water level, then start the engine.
there overheat, i think cooling system is not blended well.
can you advise please how to bleed the cooling system.
September 26, 2015
  Followup from the Pelican Staff: See this tech article:

http://www.pelicanparts.com/techarticles/Porsche-Cayenne/50-WATER-Coolant_Flush_and_Replacement/50-WATER-Coolant_Flush_and_Replacement.htm - Nick at Pelican Parts
 
bestieq Comments: Thanks for the detailed steps. Figure 9green arrow what's the name of that hose and where does it go? Had a leak changed my upper and lower hose to find out the leak is not there.
July 10, 2015
  Followup from the Pelican Staff: Looks like the small coolant expansion tank hose. Give our parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
 
David W Comments: No its not over filled, if i blow into the hose the air will leak through the cap, would a air leak in the cap cause it to spill out through the over flow pipe? i lost like 1/2 a gallon through it? if so i shall buy a new one. thanks
May 1, 2015
  Followup from the Pelican Staff: It could. 1/2 gallon seems like a little bit much. The cap is designed to hold about 15psi of cooling system pressure. If the cap is faulty it will not hold the pressure, and will cause an over flow. Also if the cooling system has an issue where it is operating at a higher than normal temperature, that could cause an over flow condition. The last possibility is an unlikely one and that is a more serious condition which would create excessive pressure in the cooling system. My advice to you is to replace the cap and make sure that you keep topping up the system, there are probably just some minor air pockets that will work themselves out over time. Just be sure to keep an eye on the coolant temperature gauge and stop immediately if it reaches the 3/4 mark (the dash past the 180 mark) I have also seen some issues with the Febi caps...if it is in the budget buy the Genuine Porsche cap. - Casey at Pelican Parts  
David W Comments: Hi, Great description.... Just wondering in figure 10, the hose the has the green arrow pointing to it, Where does it go? on my 04 model coolant seems to be leaking out, onto the tyre below. is this an over fill value? or do I have a bigger problem?
April 22, 2015
  Followup from the Pelican Staff: That is the overflow tube. Could be overfilled, and could also be from a faulty expansion tank cap. - Casey at Pelican Parts  
christina Comments: where does the CET hose connect to... i filled it up with coolant and it is just leaking straight out
March 25, 2015
  Followup from the Pelican Staff: It should run along the passenger side of the engine compartment and connect to the radiator. You will definitely need to remove the trim paneling to see it. - Casey at Pelican Parts  
Mike Comments: Do you sell a system to evacuate the air from the system ?
March 16, 2015
  Followup from the Pelican Staff: I am sure we can get you one. Give our parts specialists a call at 1-888-280-7799.

- Nick at Pelican Parts
 
Mr Bug Comments: You need to add a warning step 5 that all of your washer fluid will come gushing out after you remove the washer filler neck.
January 11, 2015
  Followup from the Pelican Staff: Thanks for the additional info. We appreciate it. I will have the article updated.
- Nick at Pelican Parts
 
Tim Comments: I pulled out the expansion tank to inspect it because I have a coolant leak. I kept the bottom hose that goes from the tank to the back of the engine attached because I didn't want to drain the tank. But as I maneuvered the tank to inspect the sides I heard Copland spilling. It wasn't coming from the tank but it seemed that because I tilted the hose that goes to the back of the engine it started leaking. Where does that hose go and what is it attached to? I can't see because it disappears behind the engine. One I moved the tank back to its original position the leak stopped. Could it be just overflow or maybe that hose or a connector that it's attached to that needs to change? Sorry for the long post
January 10, 2015
  Followup from the Pelican Staff: You may have damaged the hose or the attaching point. What year and engine do you have?

if you need a fast respone, Give our parts specialists a call at 1-888-280-7799 and they can help figure out which part or repair kit you need.
- Nick at Pelican Parts
 
tcooper Comments: This job looks like one of those 'maybe I should pay someone to do this' jobs. IT IS NOT. This is a piece of cake. I spent more time looking for my triple-square socket that actually working on it. The instructions are perfect.

If you do this project, make sure to replace the blue cap as well.

Pelican: Keep up the great 'how to' guides.
May 4, 2014
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
 

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