I've been chasing a small coolant leak on my Vantage V8 (38k miles). Overnight after being driven, a small amount of coolant would appear under the center of the accessory drive belt (I also developed the idler pulley/belt chirp). I recently replaced the thermostat, so I verified that the thermostat housing wasn't leaking.

While the amount of coolant has been minimal, and very difficult to verify exactly where it's coming from (even with the car on a lift, and the under plate removed) the water pump seems to have a small amount of play when I grab the pulley.

So, I'm assuming the water pump is the culprit. Anyone done the replacement? Any tips and/or tricks? I'll do a coolant change, as well as the updated idler pulley and drive belt while I'm in there.

Anything else to do preventatively while it's apart?

I'm a pretty competent amateur mechanic, with a shop and lift.

 

First thing, are you sure it's coolant and not condensation runoff from the A/C?

I haven't wiggled the water pump on my V8V but I can't recall any car I've had or worked on where that'd be considered normal. I believe there are 5 bolts holding the water pump in place. Are they all tightened to spec?

I did my FEAD belt and update pulley with a buddy. It's extremely helpful to have a second pair of hands to help you get the belt in place. You'll need one hand to put pressure on the pulley to give the belt slack while you're putting the belt in place, and you'll need more than one hand to get it in place - so the second person makes a ton of difference.

 

I'm going to take another look at it, as this morning there was yet another puddle of coolant under the vehicle...although it doesn't appear to be coming from the water pump...the block is not wet nor is there any dried coolant residue.


Seems as if the leak is from above the water pump on the engine's left side, with small drips down onto the harmonic balancer then to the floor of the garage.


Looks like I'll drive it to the shop this afternoon, prep it on the lift and leave it overnight. I'd much rather it be a hose or maybe the temp sender o-ring rather than the water pump itself....


Or maybe I should just think of it in Land Rover terms and let it leak, lol....


-H-

 

...and another twist...it seems to occur when the vehicle is fully cooled down, as I check it yesterday at 2 hours, 4 hours and 5 hours post drive with no leaks...only as of this morning, after sitting all night, was there coolant underneath.


-H-

 

Keep in mind when you look at it that the system is pressurized at operating temps, so a small leak can shoot a stream of water out, which can hit something and splash/redirect elsewhere.

 

I'd thought of that as well. I've run up to operating temp, put the vehicle on the lift, and waited...nothing. Waited a couple hours and looked again from the top and bottom and can find nothing. (It's driving me a little nuts, actually....)


The reservoir cap is holding pressure, and the leak is reduced or non-existent if I remove the cap once it has cooled down and release the remaining pressure.


I'm beginning to suspect an o ring or something like it that would expand when warm and contract once the block cools off completely....

 

Parked it this morning and placed white towels under the area. ..this was the result after a few hours.

 

I would buy a device that pressurize the radiator. Clean the area as best you can. Add a dye made for radiators. Put the car on a lift and pressurize the radiator to the psi of the radiator cap. Have a good light source as you look for the leak.

 

Parts came in this week and I had the opportunity to get the work done today. Turns out the leak was the coolant temp sensor O ring. (Of course this didn't appear on the parts fiche I was looking at, so I hadn't ordered it, and had to source one locally.)

Went ahead and replaced the water pump, idler pulley (the new style), along with the oil separator and new accessory drive belt. All in all a pretty straight forward job. The more I work on this car the more I appreciate its relative simplicity.

-H-

 

good work !!
did you end up doing it alone, or with a second pair of hands
as advised by telum, just curious as i will be tackling the belt and pulley
job before my car comes out of hibernation in the spring.

 

Got the belt done solo, but had the advantage of a lift. ..routed it from the top, then raised the vehicle and finished from the underside.

 

Glad it's all fixed The pink fluid was definitely coolant (sorry, just saw that post). Definitely agree that the car's overall simplicity is wonderful for a lot of the work we do on them ourselves.