Coolant leak from hose joint into throttle body

[944Turbo]

Without the pics, and assuming it is escaping from the rubber hose to throttle body join, The hose might have just gone a bit brittle or the hose clamp might have gone a bit loose, might just be worth removing the hose, cleaning up the end on the throttle body maybe removing a short bit of hose (if there is slack) and reseating.

Tony

 

[bmnelsc]

Generally leaks don't fix themselves although sometimes more corrosion will stop them for a while but they will return even worse. Proper fix is to remove hoses, thoroughly clean the connectors and examine the hoses for soft spots, cracks, etc. IF the hose ends are in good shape and the connection points are not cracked or eroded too badly you can probably refit and tighten the clamps. Generally you should try to put the clamps back in the same spot on the hose so you get maximum clamping action.

As a rule, you don't use epoxy on a hose joint - the hose should seal to the connector. If you must use something you'll want a flexible sealer that can cope with the expansion of the hose when it gets hot. If the leak is actually a crack in the plastic part then you might try epoxy to seal that up.

 

[MJL944]

Thanks gents.

I can't get pics to upload but please right click on broken links in top post and choose view image to see the joint I'm referring to.

Just to clarify, I'm not talking about a leak from the hose clamps areas but it's more the bit on the end of the hose that inserts into the throttle body metalwork that seems to have been forced apart slightly. Sorry if I'm not explaining it very well but the pics will reveal better than my useless words!

 

[MJL944]

Gents, your advice please.
My S2 has started to very slightly leak coolant from a joint on one of the small coolant hoses that go through the throttle body.
After it's weekly Sunday morning outing, there is currently a leak of 1 or 2 drops of coolant from the joint onto the top of the throttle body soon after the engine is switched off - i.e. during the cool down phase.

Please see these photos:

1st photo - note how the joint between the throttle body metalwork and the coolant hose 'nipple' (as Bruce usefully refers to it in his reply below) isn't flush - there's a 1-2mm gap and this is where the coolant droplets escape from. I assume pressure from inside the throttle body/under this joint has forced the joint apart slightly.

2nd photo - this is the rear of the joint shown in the 1st photo and the coolant droplets escape here from the rear and trickle down onto the top of the throttle body - you can clearly see the dried pink staining of freshly leaked coolant on the throttle body metalwork (middle of this photo).

I'm not so concerned by the very minor loss of fluid but my main concern is this:
Is this leak a precursor to the joint blowing-off? Has anyone experienced such a leak and had this joint blow-off?

Has anyone had such a leak suddenly get a lot worse?
Is the fix for this straightforward as in pull out the hose and apply some kind of suitable epoxy prior to refitting? An internet search on this leaks reveals a couple of US forum posts saying 'pull apart, clean, apply JB Weld'.

Many thanks,
Mark

 

[bmnelsc]

Thanks gents.

I can't get pics to upload but please right click on broken links in top post and choose view image to see the joint I'm referring to.

Just to clarify, I'm not talking about a leak from the hose clamps areas but it's more the bit on the end of the hose that inserts into the throttle body metalwork that seems to have been forced apart slightly. Sorry if I'm not explaining it very well but the pics will reveal better than my useless words!

It is hard to tell from the photo but I think I understand what you are saying. It is still possible it is the hose (right side) that is above the area you are talking about that is dripping down onto the fitting I think you are describing. Worth a check. Also looking at the large hose to the left - the clamp there has been removed and reinstalled slightly out of alignment of its original position (you can clearly see the depressions in the hose where the clamp was originally installed). There is also some coolant staining on the large clamp. Either way - if the hose nipple that enters the throttle body is leaking or (hopefully) the hose connection to that nipple is the source of the leak you will have to disassemble to see whats going on there. If its the nipple and not the hose you might be able to seal it up but you'll still need to remove it so you can clean it thoroughly. Remember that the S2 cooling system is pressurized to 19 psi (rad caps are rated for 19 psi) so dabbing on sealant probably wont solve your problem.

 

[MJL944]

Thanks Bruce.

It is indeed the 'nipple' joint that is leaking - thanks for that useful term as I was struggling to describe it!

I've got the photos working now in the top post and updated my description of the issue.

The 'staining' you see on the large clamp is just a reflection of the red cap in front. The leak is 100% just from the nipple connection which appears to be being forced apart slightly under pressure.

Forgive my ignorance but is 19 psi high for a coolant system? It is exactly my concern that this joint will just blow-off under high pressure in the middle of a journey so other owners experiences of a similar leak would be very welcome.

When engine is cold I can apply full downward pressure from my finger to the top of this joint and there is no play - the joint is rock solid.

Thanks,

Mark

 

[bmnelsc]

Is 19 lbs high? Yes for pre '90s and probably most 90's cars. The late Porsche models run very high - believe I read about 27 lbs. Nothing like putting a lot pressure on plastic parts that go brittle with heat cycles

As for leaks suddenly going bad - my S2 had a "one time" mystery coolant loss with no identifiable source and after a coolant flush the plastic hose adapter on the water pump started peeing like the little boy fountain in Copenhagen. O-ring shot - when I changed it the old o-ring it was pretty much damp dust...

It would be worth checking the PET to see how that adapter is attached to the throttle body...might be an o-ring in there too.

UPDATE - Looked at PET and shop manual - no o-ring. That piece might be one of several "connecting piece" shown in the PET but as it doesn't show what components it connects to it is impossible to tell. The cooling section part of the shop manual was no help either (to me at least) in determining how those hoses are routed and to what as the photos appear to be different models. While Turbos are obviously different it appears that the pre S2 models are different also.

 

[bmnelsc]

Any updates?

 

[MJL944]

Sorry Bruce, I hadn't seen your update to your last post.

I did have a look on PET and came to the same conclusions as you, namely that there's no O-ring and that you can't tell what the piece is that I'm having trouble with from the PET diagram. [It frequently amazes me how unhelpful many of the PET diagrams are - that page without additional notes is at best unhelpful. I suppose that's why so many 'parts guys' in the motor industry are so miserable and hostile!]

I did share the photo of the coolant leak with my local specialist this week who stated that 'it's actually a fairly common issue' and that it's a 'problem with the throttle body rather than the coolant hose or [nipple] joint on the hose'. To try to sort it all they can really do is 'carefully pull the 'nipple' out of the throttle body and clean the area inside the metal tube that the nipple sits in ('it's an interference fit' apparently) and reseat it' but he wasn't convinced that would sort the problem completely. This leads me to think the nipple connector might be part of the throttle body itself rather than part of the coolant hose.

There was mention of needing to source another good throttle body if the leak was still apparent after the proposed clean and refit.

They weren't sure if any of the various throttle body rebuild kits that exist contain parts to help cure this issue - they'll investigate if the fix fails.

Reassuringly though, they did say they've never known the joint to blow apart completely so we've agreed to hang fire until the car comes to them in the autumn for a service and some other small bits.