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Replacing the Coolant Reservoir on a MY99 996

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Replacing the Coolant Reservoir on a MY99 996

Start by removing the air filter/metering unit. Two clips hold the Air Fuel Meter cable in place. Disconnect AFM connector and set aside.Remove single bolt holding AF assembly (13mm) and tilt unit back to remove. Set aside. Remove 2 bolts and 1 nut (10mm) holding air pump. One nut holds the Coolant Reservoir. Set aside. I used some string to pull it away from CR. Drain antifreeze by means of drain plug at the bottom of engine. Drain just enough to empty CR, then a little more. I used an a


Edited by ninerguru
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  • 1 month later...
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I would add the following to help others attempting this ... please read the above and the below completely BEFORE starting your work. You'll thank yourself !

Getting the tank out

  1. I'd remove the air pump instead of tying it to the side as above. Its very simply and takes 30-40 seconds. It gives you room you REALLY need. Plus you won't break the air hose by bending it too much.
    NOTE: There are two screws that hold the air pump in place - at the bottom. In my case I found out that the nut thse screws go into had fallen off during removal. The nuts are 'suspended' in a rubber tube and age/temperature had made the rubber brittle and the nut had just fallen when I took the screw out. I simply got new speed nuts (2x : part number: 999.500.078.00 : $2) and used them to fit the air pump back again. Its worth taking the air pump off even if you now need to buy $2 more of nuts when ordering your tank - it gives you a lot of room you need !
  2. To remove the coolant reservoir easily out of its harness, slide it towards the engine (i.e. move right) by around 1/2 to 1 inch. Then move it DOWN and out of its rail/holder. There is no need to slide it COMPLETELY (3-4") towards the engine completely as it first appears. The railings have tabs and gaps to facilitate such removal/installation. You probably won't even have that much room to slide it out completely !
  3. When draining the coolant from below the car, you'll need a bucket to keep most of the coolant and may need to empty the tray below into the bucket. Use 2 trays so you can empty one when the other is below the car. The coolant drains fast, so you can't use just one without making a mess. Also, there is a lot of coolant, almost a bucketfull.
  4. Coolant is a corrosive liquid - keep it off the paint. If you drop some on the paint, don't panic, just wipe it off with water and a cloth. Use gloves if possible.
  5. The drain plug for the coolant is close to the rear bumper, don't search too deep inside near the transmission etc !
  6. There is a coolant level sensor at the bottom of the coolant tank. Its deep and tough to see and you may break it manupulating the tank of get it out of the engine compartment. I'd recommend you reach down and remove it as follows.
    - when reachable, turn the sensor by 1/4 turn from towards you to towards the engine.
    - pull the sensor out from the bottom (it needs 2" to fall out, its 2.5" tall).
    - keep it somewhere !
    If you do break it (likely), its around 10-18 bucks, so don't panic !
  7. Lastly, be patient in getting the tank out. Its not difficult but simply time consuming. Be careful not to bend/break other hoses while you try getting the coolant tank out.

Putting the new tank back in place

  1. When installing the new tank, I found it easy to first install the sensor at the bottom and then twist-lock it (1/4 turn). The electrical connection should point towards the right taillight.
  2. First try to get the entire tank in the volume reserved for it in the engine compartment. Don't try to directly fit it in.
  3. Make sure you don't leave any tubes/connectors behind the tank during installation. The last think after installation is to realise you need to get it out to rescue a forgotten tube.
  4. Now you want to get the tank back in its harness. The harness' as well as the tank's railings have gaps to ease removal/installation. What worked good for me was

    1. rotate the tank anti-clockwise by 10-20 degrees when inside the cavity/volume of engine compartment
    2. position the right most tab of the tank sticking out of the harness while keeping the other two tabs (on the tank's top) positioned to fall in the gaps between the harness' tabs. Try feeling the gaps with your finger to know where the tank's tabs should land.
    3. Slide a 1.5" diameter metal tube at the bottom (running front -> back) slightly to the left (or right?) so that the level sensor wouldn't be obstructed upon rotation. It should gently slide out of its holder.
    4. Now level the tank (i.e. rotate it clockwise by 10-20 degrees). The tank's tabs should have fallen where the harness' gaps are and the tank will be one tab sticking out (out = towards the engine)
    5. Finally move the tank gently away from the engine, in its final installed position

[*] Slide the metal pipe back into its clamp

[*] Connect everything else just the reverse as removal.

After everything is installed

Once you have the new tank in place, you will need to refill it with coolant and 'bleed' the coolant system. Fill the coolant tank with existing/new (porsche recommended) coolant to the max level and close the coolant tank lid. I simply filtered my existing coolant with a old (but clean) cotton t-shirt and poured it in using a funnel. Then, to quote Loren, "Lift the bleed valve."


"Start the engine and allow it to get to full operating temperature (I also ran the air conditioning to force circulation). The coolant warning light will likely start to flash. Shut the engine off and WAIT until the engine and coolant has cooled enough to remove the coolant tank cap. Then add coolant to the tank and repeat the process. You made need to do this 2-3 times. When the coolant level fails to fall then the system is bled and you can close the bleeder valve."

About bleeding the coolant system.

  • Close the bleeder value after about 40 minutes (total) of good driving. You shouldn't ride with it open for more than this (my Porsche tech told me this).
  • You MUST wait for the coolant to cool between your 2-3 tries, else you won't be filling the tank completely (coolant contracts as it cools). I've had to wait for over 3 hours to cool. If you try before this then the coolant will spill off when you open the cap.
  • You may get a coolant light even with the bleeder valve closed after a few days. This is ok and doesn't mean you cracked your tank or something again. Basically there was some air trapped and the car "burped" it into the coolant reservoir, triggering off the coolant light. Wait for 4 hours for the car to cool and then top off with coolant+water (replacing a lot) or just water (replacing just a little).
  • If even after 3-4 top offs/"burps" you need to keep adding coolant, have it checked for other leaks in the coolant system.

In the end, once you've done it, please pat yourself on the back !! Great job :thumbup: !! Even my service tech. at the local dealership said its not a simple job. Its worth doing it on your own if you suspect you're losing coolant.



Edited by siddharth
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  • 7 months later...
  • 1 month later...
Quick question,

What is the AFM, and where is it located ?

Are there any line drawings showing the various components that are refered to in this DIY ?


I think he means the airbox ... when you open the rear, its bang in front of you. The airbox houses the airfilter and the mass air flow sensor (and its wire).

I don't think you need the line drawings ... I'd recommend you take a print out of this page (or save an offline copy of this page on your laptop in your garage). Then take some time off and just get started on this. What you would see then and having this DIY should get you thru ... I'd believe !

Edited by siddharth
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  • 2 months later...
Unless you break something else - all you should need is the proper tank for your model year AND model type (i.e. C2, C4, C4S, etc.). I like to replace old spring type clamps with the screw type but that it is up to you.


Thanks Loren, how many and what sizes clamps should I get for a 99 C4? - these are the same ones from Home Depot right? - Also, any hoses or other things I should replace while I am doing this mod? Thanks again.


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  • 3 weeks later...
  • 1 month later...
Thank you!

2002 C2 Cab

Just got done replacing my coolant tank. I found that I needed to lower the engine about 3 " in order to fit the larger coolant tank into the cavity. Once I lowered the engine it poped right in and everything was connected and tight within 20 minutes.

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First of all, I want to commend Loren for the GREAT DIY instructions here. I have never done a DIY project, and this was my first. I printed out the text and the pictures and had them on a table next to me...and went right down the line. Having no experience in this sort of thing, the one thing you lack is CONFIDENCE...the fear of messing something up. No sweat, you can get thru this. What I did that isn't covered here is order another sensor that comes out of the bottom of the coolant tank. You can break this by catching it on hoses and wiring...so an extra is a nice insurance policy to have. Otherwise your car is out of commission till you get one in about 4 days. I also disconnected the wiring harness from the sensor rather than try to take it out with the wires attached to it. Someone in another forum also suggested getting two of those heavy aluminum turkey roasting pans to drain the antifreeze into. They're flat and easily slide under the car...when one starts getting full, just slide it out of the way and stick the second one in there. It also makes it easy to pour the antifreeze back into the car because you can bend the aluminum pan and make a pointed pour spout.

Remember...it's really a matter of a little confidence and patience. Oh yes....I also used my extensive crude english vocabulary during the process. Make sure you check and see if the neighbor lady is outside first.

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  • 2 weeks later...

Hello all,

I also have the dreaded coolant tank leak and am looking to change it out myself. In searching the archives some have said that the '02 3.6L change might be a little more difficult requiring:

1. Cutting one of the tabs off the new tank to get it into position.

2. Lowering the engine to create more room to place the new tank.

For the life of me I can't find a picture of which tab to cut or instructions on how to safely lower the engine. If anyone has more specific tips or advice I'd be most appreciative.



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  • 4 weeks later...

It finally caught up to me too...while running errands, I return to my car to find it dripping the precious (and for some reason it is like green gold from porsche) green blood that runs through its german veins. After some research on the net and a brief chat with the porsche service tech, I come to the conclusion that the coolant tank is cracked.

I am going to change this on saturday but needed some advice regarding the coolant itself. I figured why not just do a complete coolant change while I have it out. Porsche charges a steep $45 per gallon...can i use any PHOSPATE FREE coolant? Any alternate coolant suggestions? Tips on a thorough coolant flush?

Thanks in advance,


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  • 3 weeks later...

Just finished the job...not that hard but you need some patience. took me just over 2 hours. removing those fuel lines are the key to the tank sliding in and out. after inspecting the tank i did locate the crack...it was on the bottom of the top tier of the tank right in the seam.

thanks for the great diy instructions and the savings of about $500...that will go to my new clutch which i think i will try to do myself too. i read a diy on the rms and during the re-installation for the clutch i didnt see any adjustments that were needed. is the clutch just a bolt off bolt on job?


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Just finished the job...not that hard but you need some patience. took me just over 2 hours. removing those fuel lines are the key to the tank sliding in and out. after inspecting the tank i did locate the crack...it was on the bottom of the top tier of the tank right in the seam.

thanks for the great diy instructions and the savings of about $500...that will go to my new clutch which i think i will try to do myself too. i read a diy on the rms and during the re-installation for the clutch i didnt see any adjustments that were needed. is the clutch just a bolt off bolt on job?


and i didnt break that sensor from the bottom of the tank....whew!

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  • 3 weeks later...

A few issues have come up while I was attempting the process of replacing the coolant tank. I hope someone can help.

Issue #1 : involves loosening the bolts on the air pump. As I removed the bolts, the nut holding the bolt on fell into the cavity where it was attached from underneath. I can see the nut but I am not sure how to get it out and there after how to thread the screw back on to the nut. See Pic below labeled “Issue #1” below for the location I am talking about.

Issue #2 : if I loosen the fuel lines as described at the beginning of this post – quoted here >>>… “There are two fuel lines that will prevent you from removing the tank from the engine compartment. Loosen (17 & 19mm) them and tuck away”. If I do this will fuel come out of this line? If so, is this recommended?!?!

Issue #3 : See the pic below labeled “Issue #3”. What is that? Should I do anything with it to properly remove the coolant tank?



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Issue 1 - Did you read the comments in post 2 item 1. He talks about loosening the air pump nuts.

Issue 2 - You won't likely be able to get the old tank out with removing the fuel line fitting. Yes, a small amount of fuel may come out out - just becareful and no smoking.

Issue 3 - You must have a C4. On a C4 the fuel filter (silver canister) is mounted on the coolant tank and will need to be removed. There is a screw clamp that holds it in place. Just loosen the clamp and the filter can be removed and set to the side.

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Ok - so as frustrating as this is - I finally have the new tank back in place. :) yahooooooo!. I got everything roughly back in place (just have to tighten the nuts and such. I decided to order a new fuel filter - for under $30 I figured, I might as well replace it now since I have decent access to it now and don't want to do this procedure anytime soon. It should go back in place pretty easy from here - meaning tightening everything down and checking to makes sure nothing was left out.

One thing I decided to do was to do a complete refill of the antifreeze instead of just putting the old stuff back in. I am going to pay a local dealer $90 labor (I supply the antifreeze) to do the vacuum refill. Does that sound like a lot?

Thanks for this post in helping me install this tank - saved a lot of money and I feel reconnected to my car. Cute little thing!!

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  • 2 months later...
  • 2 months later...

Ditto on the thanks for this DIY. Saved me about $500, and, though tedious, was not a difficult job .... as Porsche maintenance goes. A few points:

1. Either the coolant has decreased in price, or I continue to have good luck with Hennessy: $33. per gallon.

2. On the other hand, even with PCA 10% discount, tank for my MY00 was $275.00

3. I wholeheartedly agree with Loren: change to standard screw type hose clamps. Makes re-assembly much easier.

4. I agree that taking out the air pump, rather than tying it back is much nicer.

5. I had to remove the level sensor from the bottom of the tank to remove the tank. I had to reinsert the tank into its general space without the sensor in place, then reinsert the sensor in the bottom by feel. Its very close getting the necessary 2+ inches of clearance to do so. The tank simply would not roll upright (toward the engine) with the sensor hitting the fuel line fitting. Read the post above that gives specific movement directions for removing the sensor blind.

6. The turkey pan works well to catch the coolant, but take it seriously when a previous poster states that the coolant comes out with force. It will splash everywhere until a few inches have accumulated in the pan.

7. The most difficult task for me was reinserting the tank mounting tabs into the receiving tabs on the car. Even with the great, specific instructions, it just would not go .... until suddenly it was in without me knowing why.

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  • 4 weeks later...
Thank you guys, first time working on my 2000 996 carrera and I loved it, you guys made it too simple!

I also have a leak coming from around the tank area. One problem, the coolant tank was replaced a few months ago and therefor is new ! I came back from a "spirited" run to find coolant dripping quite badly from very close to the top of the black overflow tube (Under the top of the resevoir lip). It looks like the coolant is "tracking" around the back of the resevoir and dripping down beside the overflow tube? No coolant is coming out of the overflow tube. I cannot see where the leak is coming from. Could it be the new tank has failed, or is there a coolant pipe leaking that would allow the coolant to travel around the top / back of the reservoir and drip off the lip?

Any help appreciated.

Edited by tomf
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