Coolant leak

Falcon_LS · Sep 29, 2009

Last week, I did a valve job on my truck and everything went well. Although I kept noticing the expansion tank was low on coolant. I would add about half a litre or so every day. No signs of oil in the coolant or coolant in the oil, thank goodness.

I've been checking for leaks like crazy, but have been unable to identify any and it's driving me crazy. Finally, when I was coming out of a high school reunion yesterday, I noticed coolant was dripping from my skid plate, underneath the engine. I wasn't able to go under it and check right there and then, so I drove home and put the truck on ramps to go underneath, remove the skid plate and check - no sign of any leaks.

The weird thing is though, I can hear liquid flowing behind the dashboard. I reckon if the heater core was gone, coolant would leak from behind the engine.

The water pump has 70,000 km (43,750 miles on it), and I reckon if it was the water pump, it would leak every time I kill the ignition. All the hoses and everything else are tight and there's no sign of any leaks behind the engine.

I've also checked the obvious hoses, etc and I still go nowhere.

Any other ideas as to where I could check? Mechanic recommends stop leak, but having spent $800 on the truck, I'm not keen on using a $2 stop leak to fix the problem. I want to solve the problem right from its core. Thanks!

Colt45ws · Sep 29, 2009

A lot of times you will hear liquid flowing in the heater core if it has air in it.

eljefino · Sep 29, 2009

Sounds like a pressure test would help find your leak. Evaporated antifreeze usually leaves a flaky white deposit. I'm thinking an end tank of your radiator isn't quite sealing...

Jim 5 · Sep 29, 2009

These leaks are hard to find because the hot engine parts evaporate the coolant as it leaks out.

I had a similar problem on my '89 4Runner and found it by getting under the car and having my buddy shut it off. A short blast would shoot out and immediately evaporate from the lower rad hose. The radiator had been replaced recently and the mechanic had failed to tighten the gear clamp on the hose.

I couldn't see any deposits there when I went in to tighten the hose, but you could see it vaporize on the hot radiator tank as soon as it shot out. You'd only see a tiny puddle on the ground (easily missed) as evidence. It only did this little shot the second the car was turned off.

Silk · Sep 30, 2009

You didn't do the water pump - ALWAYS do the water pump on a Mitsi V6 if you have it down that far!

You have an air lock.It's also possible the heater core is blocked - pull a hose off and see how much flow there is at idle,just putting the garden hose on won't give a good idea.I use a Lisle coolant funnel http://www.amazon.com/Lisle-22150-Spill-Free-Funnel/dp/B0002SR6WK to cure air locks....best tool I've ever bought.

StevieC · Sep 30, 2009

Water pumps on a 3.0L are very reliable if done right and can last almost the life of the engine.

PT1 · Sep 30, 2009

Run your oil about 3000 miles and do a UOA at Blackstone to see if there is evidence of coolant in the oil to rule out an internal gasket leak. I always do this with every vehicle at 10,000 miles before warranty expiration.

mechtech2 · Sep 30, 2009

Talcum powder, baby powder, or even flour can be dusted over the suspected areas.
There will be a nice trace where any fluids are leaking.

Jim 5 · Sep 30, 2009

Good idea. I'll remember that one.

lipadj46 · Sep 30, 2009

Just dump a little bottle of uv coolant dye in your expansion tank/radiator. With a black light it will be really obvious where your leak is coming from.

Silk · Oct 1, 2009

Originally Posted By: StevieC
Water pumps on a 3.0L are very reliable if done right and can last almost the life of the engine.

No they don't! More Mitsi V6 engines have been destroyed by a faulty water pump than any other cause.

StevieC · Oct 1, 2009

Maybe where you are but not over here... I have a Caravan in the driveway that has over 300K KM on it with the original pump.

We have done more timing belts and overhauls on these model engines than I can remember and the water pumps only give us problems on rare occasions.

That and when these water pumps do fail they tend to leak or make a whining sound for quite a while before the pump gives up completely so IMO the owner had ample chance of replacing it.

How many have you experienced?

Silk · Oct 2, 2009

Heaps - I work at a Mitsi dealer,and 11 years in my own business before that.My own Diamante I got from a customer after a water pump failure - both heads were destroyed,and on stripping the engine found the crank badly scored to

ften the pumps seize,stripping the belt and causing even more damage.I don't think you would find any workshop or dealer not replacing a water pump on these engines doing a cambelt or removing cyl heads.

StevieC · Oct 2, 2009

Maybe because we have cold weather for the majority of the year and that is why we see less failures... I have never encountered the stories you guys have. Very interesting...

brianl703 · Oct 2, 2009

Originally Posted By: lipadj46
Just dump a little bottle of uv coolant dye in your expansion tank/radiator. With a black light it will be really obvious where your leak is coming from.

Some coolant already glows brightly under a black light, no need to add any dye.

Silk · Oct 2, 2009

Originally Posted By: StevieC
I have never encountered the stories you guys have. Very interesting...

Before 1990 we ran our cars for a very long time,not as bad as Cuba,but pre war cars in in daily use well into the '70's.After 1990 we sourced used Japanese domestic vehicles,this killed our own assembly industry and made cars cheap....and older cars cheap to the point of being disposable.They are run into the ground and maintenance minimal - I've seen cars dumped just because a water pump replacement is more than the car....and not just old wrecks,these are otherwise good vehicles.

lipadj46 · Oct 2, 2009

Originally Posted By: brianl703

Some coolant already glows brightly under a black light, no need to add any dye.

I have seen coolant that glows a bit under a black light as does some other fluids. No comparison to the dye though that will stay after the liquid has evaporated and mark a leak.

artificialist · Oct 5, 2009

Originally Posted By: Silk
Originally Posted By: StevieC
I have never encountered the stories you guys have. Very interesting...

Before 1990 we ran our cars for a very long time,not as bad as Cuba,but pre war cars in in daily use well into the '70's.After 1990 we sourced used Japanese domestic vehicles,this killed our own assembly industry and made cars cheap....and older cars cheap to the point of being disposable.They are run into the ground and maintenance minimal - I've seen cars dumped just because a water pump replacement is more than the car....and not just old wrecks,these are otherwise good vehicles.

Half the problem is that newer cars reqire much more work to remove the water pump. Back in the old days, you could take the accessory drive belts off, and the fam off, and the old pump would come out without any trouble.

Newer cars can require moving the alternator and P/S pump out of the way, loosening engine mounts to move the engine around to have enough space to use your wrenches, taking the crank pulley off, taking the timing belt or chain out, then finally the water pump can be removed and installed. Next the timing has to be reset, and then finally the car can go back together. I have seen many water pump replacements cost $1500.

And don't blame the Japanese for this. The GM Quad 4 and Chrysler 2.7 are often more difficult than water pumps found in Japanese cars. There are very few German or Swedish cars where I live, so I can't comment on how difficult their water pumps can be.

Coolant leak

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