After going out for a run in my 996 C2 and getting stuck in heavy traffic on a hill where I had a lot of stop/ start in hot weather, I got home and noticed there was coolant leaking from the rear left of the car. It's never lost coolant up to this point and I assume the it got quite hot and found a weak spot. Can't tell for sure but looks like it's leaking around the water pump gasket.

I have ordered a replacement pierberg pump and also a thermostat. It seems harder to get the full range of brands in the UK and had to order from Germany.

I watched a few videos and trawled the forums and it appears to be a reasonably straightforward job though I'm sure I will come across the usual challenges!

More confusing seems to be the subject of coolant, I've read conflicting forum comments on what's best to use. But Prestone seems like a good option and I believe that's what in the car currently as its a luminous yellow/ green colour.
The recommendation seems to be to be to use a compressor to flush the cooling system which I don't have so many need to borrow one for that job.

I also can't seem to find the correct hose clamps to replace the current ones. Again, a lot of forum posts state that the original type should be used and not screw clamps.

Any thoughts or recommendations before I start would be much appreciated!

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Use Pentosin red if you can get it. Or Porsche stuff.
Use the Airlift system to fill it.

 

You could look for screw/bolt hose clamps. They won't cut into the hose. Also agree with yelcab. Get the Pentosin and mix with distilled water. The suggestion to get an airlift system to fill it requires an air compressor, but maybe this is a good reason to get the air compressor. Comes in handy for a lot of things.

 

Porsche moved to a newer screw-type hose clamp. You can use that as long as it’s the Porsche clamp. Porsche went this route because it’s a slight improvement. The old clamps can lose clamping force over time. That seems like the only downside besides having to use a different tool to properly remove and install them.

Do not use the cheap screw clamps found elsewhere. They are either crap metal or rust-prone, and can deform (out of round) and even leak or crack a metal hose. These are actually worse than the original tension-style clamps. But the best ones are the newer style Porsche screw clamps.

 

Nothing is worse than the tension type clamps. The two ears always face the wrong direction. Or they spring to the wrong direction when your pliers slip off. Even when they face the right direction and you have reused them, they lose enough tension that they leak at working pressure ... leading to you having to do the job over again.

Remove that piece of crap of a clamp and replace with screw type clam of good quality. The Oreily's ones have always worked for me. Norma clamps are also good.

When I remove any of those tension clamps, they go right into the garbage.

There is one thing that is worse, the Otinger one time use clamps. You have to cut them off, they cannot be reused, and you cannot readily get them at the autoparts store.

 

Thanks all that helps with the clamps, I'd got it into my head from reading other posts that the screw type clamps were a bad idea but I see the Porsche ones are readily available on the design911 website (I guess the closest to pelican parts we have in the UK). There do seem to be some differences of availability of brands. Pentosin doesn't seem to be readily available in the UK.

 

The benefit of the spring clamps is that they maintain clamping force even though the rubber will creep (the indentation you see in the rubber left by the clamp after its removal) over the years and reduce the diameter of the hose where the clamp sits.
The screw style clamps otoh loose clamping force over the years thereby increasing the risk of a leak.

If that is enough of an advantage to outway their disadvantage and stick with them, is a personal choice.

 

My personal experience with the spring clamp is on a Cayman, one of those clamps (re-used) started to leak 2 weeks after the waterpump replacement. I had to pay a visit to the customer's garage to find it, having it towed to my place, performed a pressure test to find the leak at the old clamp, and replaced it. There was no more profit in that job. Eversince then, every one of those clamps when removed gets thrown away, immediately -- no second guessing. I have never had to replace a screw clamp when done right.

As for indentation of a hose by the screw clamp, that is why hoses get replaced pre-emptively before they leak. They do not last forever.

 

When I refreshed my cooling system, I ordered all new clamps from the dealer - they were all superseded to screw type clamps.

 

If you can't find Pentosin, Prestone makes a pink European coolant that masy work as well.

 

Why are you so inclined on it being pink color?

 

I use the Porsche stuff. its just not that much more and its always in stock and I don't like mixing brands..

My simple view of the cosmos... LOL

 

Pentosin also doesn't seem to be common in the UK, so having done some further research I have gone for Comma G30 as this seems to be good quality and readily available.

I have delivery of the Pierberg pump, Metzger thermostat and replacement aux belt, just awaiting some coolant hoses and OEM clips and will be giving it a go.​​​​
One other thing I have noticed is there are two metal pipes that appear to connect to lower inlet manifold (I think). They are quite rusty and the plate they connect to is very corroded.
I can't work out from any diagrams what they are. Below is an image from the internet I found and have highlighted what I am referring to.

Any ideas?

 

Those 2 tubes and rusty plates make up the bracket for the exhaust silencer. One on each side, part 17 and 18 in the diagram.

What you're referring to as intake manifold is actually the exhaust manifold (#1 and 2)

 

Those are the supports for the muffler.. Steel tube welded to a flat plate, no real corrosion protection and its not helped by the heat from the headers.
While I had my motor off being rebuilt I sanded them and repainted with 1500 degree silver paint.. They are NLA from Porsche.

You have to pull the exhaust system to get them out, and fair warning,, I "only" broke 1 header bolt when
I pulled my engine, the guys at flat 6 and the guy that did the heads were impressed.. They said the average was 1/2 of them..

If you want to take them out,,, slow and steady, the one I broke was the last one and I got in a hurry..
heat, pb blaster heat pbblaster gently tug with wrench, then I used small round drift punch and tapped
in the middle of the bolt with a tiny tiny ball peen,, heat pb blaster. test repeat... About 10 min a bolt..
I used a small tip MAPP gas torch so I could get the heat in the bolt quickly,

I also used a small impact driver with the clutch all the way loose so I could put some vibration in a couple of them. But the heat cool cycle won the race.