Front Crossover Pipes and Hoses

[Sennajc]

Appreciate some advice…
I have removed the 4 hoses (2 each side) from the front - 997.2. They were quite corroded but got them out cleanly from the plastic fittings to the radiators and one of the crossover fittings. It was a bigger struggle to remove from the aluminium crossover pipe on each side but I managed it and the remaining aluminium housing is in ok shape...signs of corrosion!!

I really want to avoid replacing the crossover pipes (I don't have the facilities to do it!) but want to be sure I get a tight seal when I fit the new hoses. Has anyone any suggestions for ensuring the seal is good?
I thought about adding some silicone sealant to the joint when I push in the new hoses...I know it's not ideal but interested to hear if there are any reasons why it wouldn't work or some better suggestions.
Thanks.

 

[monster]

Personally I don't think trying to use a sealant is the best approach, the sealing rings within the connectors do the job of sealing perfectly well, and the usual reason they leak is when the aluminium pipe corrodes around the joint. If the connectors on your aluminium cross over pipes are in good condition then there is no need to add any additional sealant. If however they are suspect I really would advise you to replace the pipes rather than try and fudge it with sealant.

I replaced the four rubber pipes you mention, plus the aluminium crossover pipes on mine a few years ago, its not too bad a job - I did it on my garage floor with jack and axle stands. You need to undo and lower the front subframe a bit and then spend a while working out how to wiggle the pipes out. If you have the practical ability to replace the 4 rubber connecting pipes you should be able to manage the crossover pipes too!

Then you have will the peace of mind that the job has been done properly and all the suspect parts replaced! Good luck with it

 

[KarlRS]

Suggest you view demort’s posting on coolant crossover pipes also in the 997 section

 

[Sennajc]

Personally I don't think trying to use a sealant is the best approach, the sealing rings within the connectors do the job of sealing perfectly well, and the usual reason they leak is when the aluminium pipe corrodes around the joint. If the connectors on your aluminium cross over pipes are in good condition then there is no need to add any additional sealant. If however they are suspect I really would advise you to replace the pipes rather than try and fudge it with sealant.

I replaced the four rubber pipes you mention, plus the aluminium crossover pipes on mine a few years ago, its not too bad a job - I did it on my garage floor with jack and axle stands. You need to undo and lower the front subframe a bit and then spend a while working out how to wiggle the pipes out. If you have the practical ability to replace the 4 rubber connecting pipes you should be able to manage the crossover pipes too!

Then you have will the peace of mind that the job has been done properly and all the suspect parts replaced! Good luck with it

Appreciate the thoughts!

I have it in my mind that the reason for the corrosion of the joint is that the rubber o-ring fails somewhat and some coolant weeps through and accelerates corrosion! I’m thinking some silicone might prevent that also!! However, I also agree it feels like a fudge!!

On dropping the subframe and replacing the crossover pipes, you have given me some encouragement. I am on axle stands and the garage floor…but I’m not sure how well I’d cope working on my back trying to manoeuvre the pipes etc.! The hoses are easy to do and I’ve also done the air con condensers…just wondering if the crossovers are a step too far!!
Thanks

 

[diceman]

Appreciate the thoughts!

I have it in my mind that the reason for the corrosion of the joint is that the rubber o-ring fails somewhat and some coolant weeps through and accelerates corrosion! I’m thinking some silicone might prevent that also!! However, I also agree it feels like a fudge!!

On dropping the subframe and replacing the crossover pipes, you have given me some encouragement. I am on axle stands and the garage floor…but I’m not sure how well I’d cope working on my back trying to manoeuvre the pipes etc.! The hoses are easy to do and I’ve also done the air con condensers…just wondering if the crossovers are a step too far!!
Thanks

I have a slightly different view on the reason for failure/corrosion. I suspect it is bimetallic/galvanic corrosion, The pipes etc are aluminium, the hose retaining clips are steel. Having recently changed mine some were totally shot and rusted solid, the better ones could be removed and were showing corrosion starting around the location of the spring clips. The connections located in the wheel arch area are going to be subject to far more road splash which will allow the connections in the area to conduct better for more of the time and accelerate the corrosion.

Once they get old you may well find that minor corrosion allows the coolant to leak, by design the coolant should contain a rust inhibitor and crystalise on contact with the air after some time, Porsche' "for life" coolant will have run out of inhibitor after 5+ years and IMHO should be changed and not simply "topped up" as the maintenance documents indicate. "For life" here being "for the life of the warranty" IMHO. There is no coolant containing inhibitor that will last more than 5 years that I'm aware of. I added a post about how to check the acidity of your coolant and how that correlates with the amount of inhibitor left probably a couple of years ago, having now changed my coolant pipes I feel it is a secondary failure item and not the primary cause.

 

[Bigbaddog997]

Appreciate some advice…
I have removed the 4 hoses (2 each side) from the front - 997.2. They were quite corroded but got them out cleanly from the plastic fittings to the radiators and one of the crossover fittings. It was a bigger struggle to remove from the aluminium crossover pipe on each side but I managed it and the remaining aluminium housing is in ok shape...signs of corrosion!!

I really want to avoid replacing the crossover pipes (I don't have the facilities to do it!) but want to be sure I get a tight seal when I fit the new hoses. Has anyone any suggestions for ensuring the seal is good?
I thought about adding some silicone sealant to the joint when I push in the new hoses...I know it's not ideal but interested to hear if there are any reasons why it wouldn't work or some better suggestions.
Thanks.

After assembly plaster every connection with lanoguard. Mine are original and 18 years old, no corrosion or leaks etc.

 

[911UK]

Appreciate some advice…
I have removed the 4 hoses (2 each side) from the front - 997.2. They were quite corroded but got them out cleanly from the plastic fittings to the radiators and one of the crossover fittings. It was a bigger struggle to remove from the aluminium crossover pipe on each side but I managed it and the remaining aluminium housing is in ok shape...signs of corrosion!!

I really want to avoid replacing the crossover pipes (I don't have the facilities to do it!) but want to be sure I get a tight seal when I fit the new hoses. Has anyone any suggestions for ensuring the seal is good?
I thought about adding some silicone sealant to the joint when I push in the new hoses...I know it's not ideal but interested to hear if there are any reasons why it wouldn't work or some better suggestions.
Thanks.

age and aluminum is always an issue
every car is different

 

[diceman]

I have a slightly different view on the reason for failure/corrosion. I suspect it is bimetallic/galvanic corrosion, The pipes etc are aluminium, the hose retaining clips are steel. Having recently changed mine some were totally shot and rusted solid, the better ones could be removed and were showing corrosion starting around the location of the spring clips. The connections located in the wheel arch area are going to be subject to far more road splash which will allow the connections in the area to conduct better for more of the time and accelerate the corrosion.

Once they get old you may well find that minor corrosion allows the coolant to leak, by design the coolant should contain a rust inhibitor and crystalise on contact with the air after some time, Porsche' "for life" coolant will have run out of inhibitor after 5+ years and IMHO should be changed and not simply "topped up" as the maintenance documents indicate. "For life" here being "for the life of the warranty" IMHO. There is no coolant containing inhibitor that will last more than 5 years that I'm aware of. I added a post about how to check the acidity of your coolant and how that correlates with the amount of inhibitor left probably a couple of years ago, having now changed my coolant pipes I feel it is a secondary failure item and not the primary cause.

Pics below of the various stages of corrosion. I feel this suggests the corrosion starts at the interface between the Ali and steel retaining clip.