Peculiar coolant leak issue

[Falcon_LS]

I never used premixed coolant in my truck, until I recently did a cylinder head overhaul. I always used a 40% coolant to 60% distilled water ratio, and mixed it myself (using Dia Queen or Motorcraft Premium Green Coolant).

When I was purchasing parts for my overhaul, I had a significant amount off Mitsubishi Genuine Premixed Coolant (70/30 ratio), so I went ahead and bought 12 litres (10.5L capacity overall). Thought it was more convenient as well just to pour in, instead of mix.

After I refilled the system, I noticed white traces of coolant on my distributor cap and water pump surround, going all the way to my wiper motor. I even noticed coolant coming out of my throttle body coolant hose. It wasn't worn out or anything, there was a wee bit of foamed coolant at the tip of the hose, past the clamp. I had to top up with distilled water (about 500 ml) every day. I cleaned up all the residue whilst I was topping off as well.

Now the more I topped up, the less residue was being left on the said areas and the less frequent the topping up. This went on until I no longer had to top off the coolant everyday. It was more like once every 10 days or so.

Three days ago, the expansion tank was a bit low on coolant, so this time I refilled using what was left from the premixed coolant as opposed to distilled water. As soon as I did so, the amount of residue on the said areas started building up and I had to top off frequently again (daily).

I'm quite confused, because this has never happened before. The higher the ratio of distilled water to coolant, the less I had to top off and the lesser residue. Afterwards, I had enough and flushed out all the coolant with distilled water and mixed in Motorcraft Premium Green. Problem disappeared completely - no topping up required since.

Maybe this particular coolant wasn't that well suited to my application?

 

[demarpaint]

Sounds odd, have you pressure tested the system just to be 100% certain there are no leaks after all the work you did to the engine.

 

[Falcon_LS]

Haven't done a pressure test yet to be honest, I'm looking to purchase a pressure tester to install in place of the radiator cap.

 

[mechtech2]

Weird and odd.
Pressure doesn't know what the concentration is, so leaks are leaks.

 

[Falcon_LS]

Just an update on the situation, this morning I've had to add about 200 ml of distilled water once again. I'm still trying to get hold of a pressure tester, and it's as common as hen's teeth. I'm going to try sourcing one online, from abroad.

In the meantime, I've taken my vehicle to several places, including the dealer. They either cannot find the source of the leak, or take wild guesses as to where it COULD be spraying from. Not one soul has taken out a pressure tester and inspected the system, they just idle my engine and check for leaks with a spotlight.

According to the vehicle service manual, I have to apply 23 PSI of pressure to check for leaks. Based on residue, I'm suspecting it is from either the water pump fitting gasket or, worst case scenario, an o-ring connected to this pipe running through the centre of the block (despite having replaced it last month with my head overhaul):

Both of these are a real pain to replace, and all I'm being recommended is a cooling system stop leak. Will this be of any benefit? My worry is it will plug up the radiator and cause more hassle than it is worth. At $850, a radiator isn't exactly cheap either. OTOH, I've just dumped a whole load of cash on the vehicle, and right now there are other priorities that need to be addressed...so the issue will have to wait for a while.

 

[Silk]

??? You have coolant weeping out of the small hoses on the throttle body? It's possible the interior lining of the hose is cracked - coolant traveling up the webbing between inner and outer layers of rubber - replace all hoses.If it's flicking out and going over the engine and back to the firewall,I'd say the water pump is leaking.Getting sick of hearing me say that eh?

Also disconnect and bypass the heater,and rear heater if you have one to eliminate that possibility.

 

[Gary Allan]

The O ring is a likely suspect. That would explain all the oddity of the whole thing.

It still doesn't make sense with the coolant concentration level ..but

Yes, it's a royal pain to take the intake off to replace the O ring. They could have just integrated the pipe and made it serviceable out in the open.

 

[Silk]

The pipe can be removed in FWD cars,but a bit more difficult in the Pajero.I've never done one in a Pajero,but it should be possible by removing the inlet manifold.The pipe often corrodes in the O ring groove - they need a buff to make sure there is no corrosion.

 

[demarpaint]

I'm thinking O ring. Odd no one has a pressure tester. Stop leak is always an option, a very last resort option! I'd get a pressure tester it is a great tool to have!

 

[Falcon_LS]

Just an update on the situation. My pressure tester arrived from the States this morning, and I tested my cooling system the moment it arrived!

The offending part turned out to be the thermostat hose (located above the water pump assembly, in between the thermostat (left) and the distributor (right) and the upper and lower radiator outlets). The hose can be seen in the last image I posted, right above the lower radiator hose. As soon as I applied pressure, it squirted coolant all over the place. The clamps tore a small hole into it, which wasn't visible at all. I'm absolutely delighted I didn't have to use stop leak.

Originally Posted By: Silk
??? You have coolant weeping out of the small hoses on the throttle body? It's possible the interior lining of the hose is cracked - coolant traveling up the webbing between inner and outer layers of rubber - replace all hoses.If it's flicking out and going over the engine and back to the firewall,I'd say the water pump is leaking.Getting sick of hearing me say that eh?

Also disconnect and bypass the heater,and rear heater if you have one to eliminate that possibility.


Silk, water pumps on the 6G72 engines (and other Mitsubishi engines) actually tend to last a long time here. I used to change mine every timing belt change, but now I decided to make it every second timing belt change. One of my mates has a '95 Pajero still on the original water pump with over 410,000 km on the clock!

Having said that, it's possible to replace the 0-ring on a longitudinally mounted 6G72 simply by removing the water pump assembly. I'm just chuffed to bits that I didn't have to go through any of that, and it was a simple fix!

 

[Silk]

They will probably last a long time here too,but experience on the workshop side of things means that water pumps are changed every cambelt job.It's just not worth the risk of a customer coming back with major engine failure.We don't sue people here in New Zealand,but we have a Consumer Rights Law where if say your waterpump failed not long after a cambelt replacement causing engine damage....then the cost of repair would be on the repairer.

You can get away with it yourself...but in the professional repair trade over here we say CYA - Cover Your Arse.

 

[Falcon_LS]

True, better safe than sorry! It's a straightforward job when replacing the cambelt, but not so easy when you're replacing just the pump.

 

[demarpaint]

Originally Posted By: Falcon_LS
Just an update on the situation. My pressure tester arrived from the States this morning, and I tested my cooling system the moment it arrived!

The offending part turned out to be the thermostat hose (located above the water pump assembly, in between the thermostat (left) and the distributor (right) and the upper and lower radiator outlets). The hose can be seen in the last image I posted, right above the lower radiator hose. As soon as I applied pressure, it squirted coolant all over the place. The clamps tore a small hole into it, which wasn't visible at all. I'm absolutely delighted I didn't have to use stop leak.

Originally Posted By: Silk
??? You have coolant weeping out of the small hoses on the throttle body? It's possible the interior lining of the hose is cracked - coolant traveling up the webbing between inner and outer layers of rubber - replace all hoses.If it's flicking out and going over the engine and back to the firewall,I'd say the water pump is leaking.Getting sick of hearing me say that eh?

Also disconnect and bypass the heater,and rear heater if you have one to eliminate that possibility.


Silk, water pumps on the 6G72 engines (and other Mitsubishi engines) actually tend to last a long time here. I used to change mine every timing belt change, but now I decided to make it every second timing belt change. One of my mates has a '95 Pajero still on the original water pump with over 410,000 km on the clock!

Having said that, it's possible to replace the 0-ring on a longitudinally mounted 6G72 simply by removing the water pump assembly. I'm just chuffed to bits that I didn't have to go through any of that, and it was a simple fix!

I found the pressure tester worth its weight in gold, and a good tool to have in the tool box! Takes a lot of guessing out of the job.