Coolant Loss

[Richard Lorand]

My 1998 KZJ95 which I have owned for just over a year has always needed a little extra coolant to bring it to the full mark in the header tank, probably half a pint every month. No visible signs of leaks anywhere and engine oil clean and no bubbles while engine is running with radiator cap off. Three weeks ago went down to Cornwall 420 miles mainly motorway at 70 mph and when I checked the coolant the level was still on full. Then two weeks of short journeys resulting in 160 miles it takes nearly a litre. Return journey home no coolant loss at all. Where should I start looking. I have it booked into the garage for a pressure check but I would have thought the greatest water loss would have been on the longer journeys. Advise would be appreciated.

Richard

 

[Higgy]

My old 95 had 280,000 miles on the clock, and all the years I had it I don't think there was any water in the expansion tank! .. Never any water loss in the rad.. I remember the overflow pipe from the rad was blocked solid I would regularly check Rad level before and after long miles but I don't ever remember. checking the expansion bottle.. Still runs sweet as a nut to this day..

 

[Beau]

Firstly, at what point are you checking the coolant level, when the engine is warm or cold? A cold engine will show less in the expansion tank than when it's warm.

Check the obvious radiator hoses, the hoses at the back of the engine that run into the cabin ect. But more importantly check the lines that run to the rear heater matrix (if you have rear heaters) as these are known to rust and then lead to loss of coolant.

Generally speaking you're right in thinking the motorway miles should lead to more loss of coolant if you had a issue with a gasket or cracked head. Were you using your heaters on your trip to cornwall?

 

[Richard Lorand]

I always check the level when the engine is stone cold. Heater was never used on the trip. The truck does have a rear heater but when I got the vehicle the metal pipes running down the bulkhead and under the floor were very corroded that I cut them off and by passed them.

 

[nick_the_fish]

What sort of coolant are you running? Is it water based? If there is absolutely no other signs of leakage and its not disappearing into one of the cylinders try replacing the cap on your expansion bottle. Maybe the water is evaporating off through there.

Long shot but worth a thought???

 

[Animal Mother]

My guess is a weep from the water pump.

 

[Richard Lorand]

I use one third red antifreeze mix which I replaced when I got it last year. To date it has only got 119K on the clock so barely run in.

 

[MarkW]

I had a very small leak from the waterpump on mine, generally when driving the heat of the engine caused the leak to dry up so I couldn't see it

 

[Animal Mother]

I had a very small leak from the waterpump on mine, generally when driving the heat of the engine caused the leak to dry up so I couldn't see it

I had the same issue on mine (BluePrint water pump leaking from new).

 

[clivehorridge]

As far as I can see, nobody has mentioned whether it's an auto or manual.

AFAIK, the auto ATF is cooled using the lower tank of the rad, so a coolant leak into the ATF pipe in the bottom rad tank could be filling the auto box with coolant. This is a common problem on auto 90 series trucks.

I suggest you checking the ATF level and any signs of coolant in the auto box, assuming it is an auto.

If it's a manual, then forget this post altogether.

 

[Richard Lorand]

Sorry, its the manual.

 

[Jack VZJ90]

checked the valve of your heater system under the hood ? also a common problem for minor leaks because of age.

 

[Richard Lorand]

Thanks for that, I have checked it and it is as dry as a bone. It seems to loose coolant on short journeys rather than long ones. Perhaps when the engine is hot it nips up the leaking problem. Since my last post the system has been pressure tested and nothing found. The head scratching continues.

 

[Aeroelastic]

Hi have you ever resolved this coolant leak problem?

 

[MisterCruiser]

Are you sure you have a problem?

I noticed my expansion bottle level varies quite a lot from full to empty. I used to wonder if I had an issue, I topped it up a few times but it still lowers. My rad is always full, never had to top up the rad. I have no external leaks. My mate who had a Toyota dyna said his was the same and that half the time he checked his bottle was empty, he had it for years and never any trouble so it seems to be normal, as the poster up above has same behavior. I have mine nearly 8 yrs and it's not a problem so far, normal I'm putting it down to.

I'd be weary of the mechanic diagnosing a head gasket based on this.

 

[Aeroelastic]

Hi thanks. Mine radiator is always full as well. Never need to top it up. But the expansion tank will slowly lost coolant over time. Like 100-200ml over 3-4 months. Still looking around for external leak. It doesn’t use oil, no mayonnaise residue on oil cap. No oil in coolant, Auto ATF red and nice. No bubble in expansion tank, trying to convince myself it’s not a head prob. Reading things on internet just makes your head wonders. I think it might be the water pump as it’s oily around it from the previous owner rocker cover leak so hard to tell for sure. Mine is a Prado so no rear heater pipes (I guess).

 

[MODVRS]

When I've see this come up before suspicion has been aimed at the coolant pipes for the rear heater. They're famed for rusting and because they are in the airflow a minor leak can go unnoticed as it dries out quickly. Maybe worth a look.

 

[Aeroelastic]

Thanks MODVRS, my Prado hasn’t got a rear heater, so suspect the piping from the engine bay is different? Anyone got photos of the Colorado rear heater piping arrangement in the engine bay? So I can compare mine and see if the piping source is there and check.

 

[Beastrider]

Here is mine, which definitely has a rear heater. The two hoses marked with red ‘x’ go down to the chassis and run along the inside of the RH chassis leg to the rear heater matrix. Originally, there is a combination of rubber hoses and metal pipes, but the pipes rot as MODVRS said, so most people either cut and plug the hoses inside the engine bay (and do without a rear heater) or completely replace the pipes with rubber hoses. I wanted the rear heater so I chose the latter option.

 

[MisterCruiser]

How do you quote a post on this forum to reply?

@Beastrider - I'm guessing a short wheel base colorado wouldn't have that rear heater matrix?