Finding a coolant leak

[tez]

Hi everyone,

Just wondering if anyone has any ideas of how to locate a possible coolant leak in my Pajero (6G72). The things which I have done to try and locate the leak are:

- visually checked when the motor is hot and cold to see if there are any visible leaks from hoses, fittings etc

- pressure test done twice with no noticable leak detected

- TP (?) test done to check if head gasket is leaking (checks for exhaust gases)

- oil is fine and not milky

- radiator cap and thermostat replaced

Are there any other ideas on where it could be going? It loses about half a litre per 100kms and I have run out of ideas on where the water could be going.

Another thing is, when the car is hot, the top radiator is hot to touch (which I would have expected) although the bottom radiator hose is only warm.

Thanks for reading!

[jimako]

Hi There
Check the water pump behind the timing cover, theres a pipe with an 0 ring that goes into the back of the water pump, if its leaking from there 1 litre per 100 k will easily evaporate without being noticed. it could also be leaking between the water pump and the back half of the pump....
If you havent done your timing belt lately, its a good time to do it..

Thanks

[tez]

Hi, thanks for your response. Can I inspect the water pump without physically taking the water pump out? Can I just remove the timing covers to inspect it?

[Mitcon]

I don't know about the Pajero's but with other cars I've had sometimes the leak has been hiding itself in-side the cabin from the heater core or tap.

[jimako]

Hi Tez
When you remove the timing cover you can easily see the front part of the water pump and maybee even see where its been leaking from, but then again theres a fair bit behind it that you cant see.
Once the timing cover is removed, removing the water pump isnt a big job, unless its been replaced lately, id be getting a new pump along with a timing belt, belt tensioner pully and new cam and crank seals.

Regards
Jimako

[tez]

Hi Tez
When you remove the timing cover you can easily see the front part of the water pump and maybee even see where its been leaking from, but then again theres a fair bit behind it that you cant see.
Once the timing cover is removed, removing the water pump isnt a big job, unless its been replaced lately, id be getting a new pump along with a timing belt, belt tensioner pully and new cam and crank seals.

Regards
Jimako

Hi

Thanks. This will be my next port of call. If Im going to remove the timing cover, I may as well replace the water pump as the job is 90% done. Its just removing all the bit and pieces to access the timing cover that will be a pain!

Having never done a timing belt change before as well, as long as I follow the instructions in the Gregory's manual, I'll be fine?

[6G74]

Should be - the leaking into the valley thing and evaporating was a common thing, this you will wont know or see untill its completely stripped. Further to that though, if you dont find any signs on coolant leaking, id be seriously considering the possibility of heads - which would be nice and easy to do at the time.

[tez]

Should be - the leaking into the valley thing and evaporating was a common thing, this you will wont know or see untill its completely stripped. Further to that though, if you dont find any signs on coolant leaking, id be seriously considering the possibility of heads - which would be nice and easy to do at the time.

Ah ok, I was just thinking that a leaking water pump or o ring would be obvious as the water would be coming down the front or rear of the block.

With the water pumps, most places seem to only sell the front half and not the rear. Is it crucial to replace the rear, or just ensure that the o ring is replaced?

[jimako]

Just give the surface that mates to the water pump a clean, and make sure its flat.
New o ring wont cost much, and just use some sealant on the o ring to make sure it wont leak.

[tez]

Might have found the problem. After many hours and days going over the engine and under the car for leaks one morning when the car was stone cold, I poked my hand around the rear of the engine where the valley was and felt some slight dampness. Im assuming that the water pump is leaking into the valley, although when the car is hot, or the ambient temprature outside is also quite warm, it just evaporates away.

Seems only to be leaking also when the car is parked up and the weather is cool.

[greggo]

Hello Tez.

I have just removed the heads from my 6g72 to find that number 6 cylinder has been leaking into one of the cooling jackets and pushing out my coolant. Although it may be costly to do all these little jobs at once, I totally agree with the gentleman above, and believe that you should do as many of the replacement jobs in this area as you can. The jobs themselves are not difficult but the work to get to that area of the engine is considerable.

Have fun, Greggo

[Wal]

Might have found the problem. After many hours and days going over the engine and under the car for leaks one morning when the car was stone cold, I poked my hand around the rear of the engine where the valley was and felt some slight dampness. Im assuming that the water pump is leaking into the valley, although when the car is hot, or the ambient temprature outside is also quite warm, it just evaporates away.

Seems only to be leaking also when the car is parked up and the weather is cool.

Having owned a Gen 2 Paj, and suffered the same problem I can confidently tell you that your water pump is in the process of shitting itself.The signs of this are water or dampness down the valley and a gradual loss of water from the radiator. The latter accelerates after time.

The problem is the seals in the water pump and this means that the pump will have to be replaced. If this proves to be the case can I also suggest that you replace the belts when you get it fixed as the timing cover has to come off to get at the water pump. You must be close to the 150k - 180 K mark I'd guess.

[tez]

Yep, hopefully it is the waterpump as I've got a brand spanking new one from Mitsubishi here ready to go in ($220 odd later). If the seal has a habit of deteriorating, then couldnt just the water pump seal be replaced and thats it?

Although I guess if your going to the trouble of removing the timing covers, belt and water pump, you might as well replace the items.

The NH I have has 233,000kms on it. Probably best to change both items as I am not sure if the timing belt was done at the 200,000km mark.

[Wal]

Yep, hopefully it is the waterpump as I've got a brand spanking new one from Mitsubishi here ready to go in ($220 odd later). If the seal has a habit of deteriorating, then couldnt just the water pump seal be replaced and thats it?

Although I guess if your going to the trouble of removing the timing covers, belt and water pump, you might as well replace the items.

The NH I have has 233,000kms on it. Probably best to change both items as I am not sure if the timing belt was done at the 200,000km mark.

That won't be a problem as the guy who replaces your water pump will be able to see all the belts very clearly and know whether they need replacing just by looking at them. When I replaced the timing belt at 185K in my NK the mechanic actually used a permanent marker to note this inside the bonnet.

[6G74]

Sounds like hes planning to do it himself... all that aside, for the cost of the belt and the peace of mind it brings you would be mad to not do it at the same time. To even take that a step further, with those k's i would say the same thing for the tensioner, idlers and seals...