Mysterious coolant leak

[vtwinpilot]

About a month ago, I noticed a rather big pool of coolant on the garage floor, right around the passenger, right side tire. It was a lot, a cup full, 8 oz or so. The expansion tank was way down too, so I filled it back up.

My immediate thought was the the expansion tank has a sizeable crack in the bottom or somewhere to allow so much coolant to leak. As regards a bad water pump, I thought the failure mode was that in the beginning it would just drip a bit so that there are just spots and drips that come out, not an entire glass full.

It was fine for a few days, then upon my wife comoing home and parking, same thing, although not as much, but still a decent puddle around the FR tire. Now suspecting the water pump, I removed all necessary items, incl the black plastic shielding for the drive/timing belts, and had a look at the water pump.

I expected to see coolant in and immediately below the weep hole, but nope, nothing. Totally dry, and no evidence of a long-term leak in the form of a dried white path of coolant or anything of that nature.

In the ensuing weeks, I've had to keep topping up the expansion tank. Thing is though, the leaking is absolutely not consistent. After leaking, it won't leak for, say, 4-5 days - not a single drop - then it'll vomit a glass full. As it stands, it hasn't leaked in the last week or so.

The last time it leaked a decent amount, I again took off everything in order to get a better looksie. Water pump/weep hole still dry, yet, I can see coolant down below, pretty much in line with the water pump, on the metal engine frame where the control arm attaches.

One time, about two weeks ago, after I drove it to a store, after coming back to the car, I saw coolant dripping quite a bit - constant dripping - so I looked under to see if I could see exactly where it was coming from, and the only thing I could really discern is that wherever it was emanating from above, it was making its way to the black oil filter cap because the stream/dripping of coolant was going down and dripping from that oil filter cap.

So it would seem that the water pump is bad, yet I don't see any coolant around the water pump, and nothing in or near the weep hole.

Am I being fooled, and this really is a failed water pump? I popped the expansion tank off its prongs and turned it upside down and every which way to look for a crack or coolant showing signs of a crack, but the sucker's bone dry. I cinched up the little hose clamp on the expansion tank too, but of course something so simple couldn't be the problem: I tightened that a few weeks ago when the problem first cropped up.

I've looked all over the RF inside the engine bay to look for a culprit, something like a split coolant hose, or around the thermostat, but didn't see anything concerning.

This is a 2006 with the naturally-aspirated 2.4L.

I've browsed a lot of threads on here related to coolant leaks for ideas before posting up here, but nothing seemed to be germane. Any suggestions greatly appreciated!

[Clan]

Originally Posted by vtwinpilot

About a month ago, I noticed a rather big pool of coolant on the garage floor, right around the passenger, right side tire. It was a lot, a cup full, 8 oz or so. The expansion tank was way down too, so I filled it back up.

My immediate thought was the the expansion tank has a sizeable crack in the bottom or somewhere to allow so much coolant to leak. As regards a bad water pump, I thought the failure mode was that in the beginning it would just drip a bit so that there are just spots and drips that come out, not an entire glass full.

It was fine for a few days, then upon my wife comoing home and parking, same thing, although not as much, but still a decent puddle around the FR tire. Now suspecting the water pump, I removed all necessary items, incl the black plastic shielding for the drive/timing belts, and had a look at the water pump.

I expected to see coolant in and immediately below the weep hole, but nope, nothing. Totally dry, and no evidence of a long-term leak in the form of a dried white path of coolant or anything of that nature.

In the ensuing weeks, I've had to keep topping up the expansion tank. Thing is though, the leaking is absolutely not consistent. After leaking, it won't leak for, say, 4-5 days - not a single drop - then it'll vomit a glass full. As it stands, it hasn't leaked in the last week or so.

The last time it leaked a decent amount, I again took off everything in order to get a better looksie. Water pump/weep hole still dry, yet, I can see coolant down below, pretty much in line with the water pump, on the metal engine frame where the control arm attaches.

One time, about two weeks ago, after I drove it to a store, after coming back to the car, I saw coolant dripping quite a bit - constant dripping - so I looked under to see if I could see exactly where it was coming from, and the only thing I could really discern is that wherever it was emanating from above, it was making its way to the black oil filter cap because the stream/dripping of coolant was going down and dripping from that oil filter cap.

So it would seem that the water pump is bad, yet I don't see any coolant around the water pump, and nothing in or near the weep hole.

Am I being fooled, and this really is a failed water pump? I popped the expansion tank off its prongs and turned it upside down and every which way to look for a crack or coolant showing signs of a crack, but the sucker's bone dry. I cinched up the little hose clamp on the expansion tank too, but of course something so simple couldn't be the problem: I tightened that a few weeks ago when the problem first cropped up.

I've looked all over the RF inside the engine bay to look for a culprit, something like a split coolant hose, or around the thermostat, but didn't see anything concerning.

This is a 2006 with the naturally-aspirated 2.4L.

I've browsed a lot of threads on here related to coolant leaks for ideas before posting up here, but nothing seemed to be germane. Any suggestions greatly appreciated!

you need to pressurise the cooling system which will help find the leak .. That is standard practice.
If it is any consolation , I have never found a faulty volvo water pump on these engines since they were introduced in 1990 on the 960 , that's working with them daily on a professional basis .

[bkulcsar]

I'm having exactly the same problem for about two months maybe more. Did a pressure test on the system and found out that the cap of the expansion tank was bad. Replaced it and all was fine. Until yesterday.
Will do another pressure test as soon as the weather gets a bit warmer.

[vtwinpilot]

Originally Posted by Clan

you need to pressurise the cooling system which will help find the leak .. That is standard practice.
If it is any consolation , I have never found a faulty volvo water pump on these engines since they were introduced in 1990 on the 960 , that's working with them daily on a professional basis .

Thanks, figured as much. Looking for a pressure tester right now...

And funny enough, when I'd called around looking for prices to replace the water pump - in case it did turn out to be the pump and I didn't want to DIY - one of the shops said exactly the same thing, that in 20 yrs, he'd never seen an Aisin water pump fail. I guess they make better water pumps than trannies bc I had to shell out $1500 about 3 yrs ago bc the tranny was acting up with false shifts and such and it was a bum valve body.

I'll post back up after I do a pressure test.

[vtwinpilot]

Originally Posted by bkulcsar

I'm having exactly the same problem for about two months maybe more. Did a pressure test on the system and found out that the cap of the expansion tank was bad. Replaced it and all was fine. Until yesterday.
Will do another pressure test as soon as the weather gets a bit warmer.

I'd hoped for something simple too, like a cracked reservoir or bad reservoir cap, but it's not that bc I've scrutinized the reservoir and surrounding area but see no evidence of leakage from it.

[BarryCambs]

Mine had a pin prick in the reservoir, above the cold water level. I eventually found it when I saw water dripping onto the floor when it was on the ramps with the engine running for an MOT. Once the engine was cold and the level dropped, the leak stopped!

It was literally a pin prick, you couldn't see it when I took the tank off to change it. Try filling it right up then have a look with it hot and the engine running

[vtwinpilot]

Originally Posted by BarryCambs

Mine had a pin prick in the reservoir, above the cold water level. I eventually found it when I saw water dripping onto the floor when it was on the ramps with the engine running for an MOT. Once the engine was cold and the level dropped, the leak stopped!

It was literally a pin prick, you couldn't see it when I took the tank off to change it. Try filling it right up then have a look with it hot and the engine running

Thanks, Barry. I've lifted the reservoir up and off the two sort of slots that its two tabs fit into, and held it in my hands and manipulated it every which way looking for a leak, to no avail. Maybe I wasn't thorough enough. I'll try it again.

[BarryCambs]

As I say, it was only because I happened to have the engine hot and running just after I'd topped up I saw it. I couldn't see the pin prick when I took it off, even though I knew where it was!

I had something similar on a VW golf with a leak under the manifold. That only leaked when the engine was hot. Soon as the engine stopped, the heat evaporated the coolant as it leaked, so you couldn't see where it was coming from

[barrybritcher]

oil cooler has coolant pipes on it - back of engine behind oil pan.

[vtwinpilot]

Originally Posted by barrybritcher

oil cooler has coolant pipes on it - back of engine behind oil pan.

Hmm, right, good point. I'll check it.