Coolant Leak

[GrantGam]

Hi guys,

I have a slow coolant leak in my S2 Coupe ABY. I've just been topping it up every month or so as I can't find anything obvious... There's no sign of any crystalisation at any radiator inlet/outlet points and all O-rings seem tight enough and I can't find any splits in the hosing.

I've left the car idling as to get the main rad to kick in and wiggled all the hoses but no obvious leaks.

Any advice on this would be much appreciated.

Note: The aux radiator was replaced (with a new unit) about 6 months ago so I know it's improbable that this is at fault. I also have no over-heating issues and temperature remains well below 90degC unless idling.

[irishs2]

What is the condition of the oil. Any mayonnaising on the oil filler cap ?

[GrantGam]

What is the condition of the oil. Any mayonnaising on the oil filler cap ?

Nothing obvious in the way of mayo, no. Looks okay to me. Here's a picture.

[UrS4boy]

DIY Coolant Leak Tester

Here is a link to a DIY coolant system pressure tester that is designed to find such leaks. I know I am going to try it.

http://forums.quattroworld.com/s4s6/msgs/305165.phtml

[GrantGam]

Here is a link to a DIY coolant system pressure tester that is designed to find such leaks. I know I am going to try it.

http://forums.quattroworld.com/s4s6/msgs/305165.phtml

I'm all for saving money, but not when it comes to an irreplaceable car!

"Warning about performing this test with a blown head gasket. Pressuring the cooling system could force coolant into a cylinder(s) causing a hydro lock or coolant into your oil contaminating it."

Better safe than sorry I guess...

[GazzaG60]

if your worried bout a hydro pop the plugs. use a torch check the bores out. crack it with no plugs and it will create a fountain.

its really the only way to test the system. better to know its going in there than not.

[Majorcina]

Here is a link to a DIY coolant system pressure tester that is designed to find such leaks. I know I am going to try it.

http://forums.quattroworld.com/s4s6/msgs/305165.phtml

I was trying to do something similar,but i made this on my spare coolant expansion tank cap,but it didnt work since air was coming out under the tank.I sopose to much air at once force it?
Basicly u put tester kit on coolant expansion tank,and u block the hose which originaly was on the tank?
I would need to do this since i have some small leak of water

[UrS4boy]

I'm all for saving money, but not when it comes to an irreplaceable car! Better safe than sorry I guess...

IF you have blown head gasket, you will need to remove the head anyway. As GazzaG60 suggests do this test with the sparkplugs out to be safe than sorry AND learn something at the same time.

[mike74]

I had a similar issue on my one last year; turned out the after run pump was weeping under pressure. Couldn't see anything obvious from above but you could feel the under side of it was wet all the time. Hopefully its something simple anyway

[GrantGam]

I had a similar issue on my one last year; turned out the after run pump was weeping under pressure. Couldn't see anything obvious from above but you could feel the under side of it was wet all the time. Hopefully its something simple anyway

Hey,

Can you help a novice out and let me know where I can find this pump? I'm assuming it's small and in-line of two hoses?

[UrS4boy]

Hey, Can you help a novice out and let me know where I can find this pump? I'm assuming it's small and in-line of two hoses?

If you are a novice (aka "noob" (noo-bee)) then you should have a look at and book mark the link below to the live version of my engine bay device map. Click on the device label for which you are looking, i.e. Auxiliary after-run coolant pump on the right side of the diagram in this case: (You will need the diagram in the future to answer more questions)

UrS Engine Bay Device Map (made for AANs but applies to ABYs and ADUs equally)

http://members.shaw.ca/speedtek/UrS%20Engine%20Bay%20Device%20Map.html

[GrantGam]

If you are a novice (aka "noob" (noo-bee)) then you should have a look at and book mark the link below to the live version of my engine bay device map. Click on the device label for which you are looking, i.e. Auxiliary after-run coolant pump on the right side of the diagram in this case: (You will need the diagram in the future to answer more questions)

UrS Engine Bay Device Map (made for AANs but applies to ABYs and ADUs equally)

http://members.shaw.ca/speedtek/UrS%20Engine%20Bay%20Device%20Map.html

Thanks a lot!

I'll get this checked tomorrow. Did you simply replace the pump when you noticed it leaking?

[UrS4boy]

After-run Auxiliary Coolant Pump and Fan Switch and 324 Control Module Info

I'll get this checked tomorrow. Did you simply replace the pump when you noticed it leaking?

There is no fixing those pumps. If they leak, they are dead.

Replacement is easy. Clamp off the inlet and outlet hoses away from the pump, either using hose pinch clamps or needle nose vice grips (don't over tighten). Then remove the hose gear clamps and work the hose off of the pump. (You will only lose a bit of coolant). Remove the electrical connection and remove the pump. Installation is the reverse of removal

After-run Auxiliary Coolant Pump and Fan Switch and 324 Control Module Info (from that "Map"):

http://forums.quattroworld.com/s4s6/msgs/21503.phtml

[mike74]

When you're standing at the front of the car, look behind and below the auxiliary radiator. Its quite far down but you can find it easy enough by tracing one of the coolant pipes to it. As Dave says though, if its leaking you have to replace it. Not cheap but easily enough done

[newsh]

VW T4 van uses the same pump IIRC I got mine from GSF.

Other places to look for a leak..

The bottom of the rad near the mounting bush

The bottom of the coolant expansion tank.

There's also the heater matrix (you get steam inside the car and oily windows if this goes though)

And the plastic spigot on the back of the block that connects to one of the heater matrix pipes.

Headgasket leak to combustion chamber will usually make a spark plug look crusty.

Be careful with the afterun pump if the engine is hot, they've been known to come apart and spray scalding water up at you.