Coolant leak- advice please

[Millhouse1]

Hey guys. I've noticed that my AW11 (4AGZE) is leaking coolant. It only seems to do this when the car has cooled right down. I'll come out the following morning and find a small puddle under the car. It appears to be dripping down the front edge of the oil pan. You can see a very small red droplet in the first pic (circled). I've done some research and I think it may be one of three things-

1) Leaking water pump
2) Leaking water pump seal
3) Leaking water pipe

And that would explain why it only leaks when the car is cold- when the pipe/seal contracts slightly.

Do any of you know if there are any pipes running around in that area or where it might be leaking from? I don't even have a jack so can't get under there properly to take a look.

The car is not overheating- gauge stays exactly where it should- and there is no water in the oil or oil in the water so I don't think it's a blown head gasket, although it does have a rough idle when the car has warmed up, but i guess a leak somewhere will cause this due to a loss of pressure.

Any advice or offers of help would be greatly appreciated.

PS- ignore the drops of oil in the puddle of coolant you can see in the second pic- this is a separate leak that just so happens to fall in the same place!

[*84vvt]

Try cleaning the engine around the leak /front cover
grab a mirror and light start it up and have a look to see were its coming from and go from there .

[Millhouse1]

Ok so I took it in yesterday and they conducted multiple pressure tests and could not induce any leaks. They have determined that the water pump is leaking. The water is probably running along the oil pan channel and dripping down from there. I'm relieved that it's not a leaking head gasket or anything else serious. I'll get the water pump replaced in the near future. Still a little confused as to how a leaking water pump could also drip down from the bottom of the transmission housing though, which is a distance away. I'll get the pump replaced first, then see if I have a second leak from somewhere else. Thanks for your advice though, appreciate it.

[GDII]

Don't leave it too long as a leak from the water pump internal seal can get worse very fast or be minor for a long time.
See the small hole on the housing, that's probably where its coming from as the internal shaft seal will have failed.
Also pressure testing won't always find these sorts of leaks as things expand when they get hot allowing water to pass into the gaps.

[Millhouse1]

Thanks. I believe the water pump on the 4AGE and 4AGZE are the same? Should I get a genuine Toyota one from the dealership or just a generic one from the likes of Repco? Or where would you recommend I purchase one from?

[GDII]

Get a genuine one from Toyota. They may cost more but you get a fully sealed housing unit rather than just the plate with the impeller wheel. Far less chance of leaks early on. Plus you get all new O-rings for the bits you need.
You should get everything in the exploded view at the bottom if you ask for a water pump from Toyota. Places like Repco only sell the front casing like in the colour image.

The part number should be 16100-19115 for the full assembly.
http://jp-carparts.com/toyota/partlist. ... 7&fig=1601

[Millhouse1]

Thanks, that's great!

[mickeyduck]

I would add that if your AW is a Supercharger (judging by the crank pulley it is) then the tension on the supercharger belt is critical. I have found that I need to adjust it so it only just doesn't scream at revs under full boost. In other words it needs to be done up only enough to not quite slip when you have your foot to the floor. If it slips you will hear it scream / squeal quite distinctly. If you even slightly over-tighten the supercharger belt you will make the water pump (which runs on the same belt) leak. In my opinion the superchasrger belt should have at least a few more grooves - be half as wide again - so you could have less tension (better for the water pump) but also less chance of the supercharger slipping (which has a lot of resistance at full boost). But that is a design fault not easily remedied.

I would add that this design fault might be aggravated if you fit a non genuine water pump (inferior).

So - back off your supercharger belt tensioner half a turn and see how it goes. The leak might even stop.

If it continues to leak, replace the water pump (and drive belt while you are at it) and do a number of test runs where you add a wee bit more tension each time (maybe half a turn) to the belt tensioner until the thing only just doesn't scream under full throttle.

That's been my experience anyway.

You might want to buy a jack...

[Millhouse1]

Yes I had a larger crank pulley fitted a few months back and I do think this has sped up the wear on the water pump. I was fully aware of being careful as to how much tension to put on the belt, given the increased tension it puts on the water pump, however I had to have the belt tightened as it was slipping under full boost/over 5500rpm. It seems to be quite a challenge to get the belt tension just right- tight enough not to slip and loose enough not to accelerate the wear other components. Even after the recent adjustment of the belt it has started slipping again so I tried some belt grip which hasn't helped much either. So it seems I either have to put up with the belt slipping at high revs or tighten it and keep replacing the water pump every so often! Any other suggestions?

[85AW20v]

Maybe the pump has been replaced before with something generic....

See ya
Simon

[mickeyduck]

Maybe, Simon...

You are in exactly the same place as I have been (overboost pulley etc) so you will likely find it is a matter of getting it just right - which can be by as little as a quarter turn on the adjuster.