Coolant conundrum

[mrmeme1212]

Greetings brain trust.

I've got this odd isue where my coolant seems to drop over a few weeks to around minimum but will then stay put indefinietly, every time I top it up it'll drop again over a few weeks then stop.

Never seen any puddles anywhere, cant' see any white milkies in the oil, doesn't blow any white smoke. There was (or may still be) a leak in the heater core that I plugged with some stop leak shite, I used to be able to smell coolant in the cab but I haven't at all since doing the plug. Anyone got any ideas?

Cheers,

Jay

 

[Old.Tony]

It is possible that it's expanding in the reservoir on the right hand guard and exiting the overflow until it's below the threshold pressure, resulting in the noticed reduction. There should be a hose attached forcing any overflow to the ground away from the wheel, I wonder what you'd find if you attached a bag to this - like a reasonable strength large sandwich bag cable-tied to the end of the drain hose.

A leak in the heater core might also be noticed in the A/C drain pipe (front of the left hand passenger footwell in Australia). Normally you'd notice this on the ground, because unlike some cars that drain the A/C condensation onto the exhaust, the Navara doesn't seem to do this (mine doesn't, anyway).

There are other possibilities. The radiator is connected to the automatic transmission (because the auto uses a section of the radiator as a transmission oil cooler). I had external coolers fitted and the radiator connection removed to avoid contamination of the transmission fluid. If yours is an auto, check the oil in the gearbox to see if it's milky.

The coolant is also used to cool the turbocharger AND the EGR. Either of these could leak but are unlikely to be your problem because your losses stop at a certain point, but I'll still address them.

The EGR one is simple: get an appropriate piece of pipe to fit, and connect the two hoses that are on the EGR cooler (front of the engine) to each other, bypassing the EGR cooler. If the problem has gone, then the EGR cooler itself has a hole in it (internally) and coolant will be finding its way directly into the intake manifold (likely in small quantities that may not noticeably affect performance).

Identifying a problem in the turbocharger is harder. If coolant is making its way past the seals behind the turbine, it could be joining the exhaust stream where the coolant will be vaporised (typically see temps there of 500 celcius or higher). This will just head straight out the exhaust completely unseen. A gas analyser might spot the problem - a decent mechanic's workshop will have one of these. Again, I don't suspect this as a problem because this would continue draining the coolant.

 

[mrmeme1212]

It is possible that it's expanding in the reservoir on the right hand guard and exiting the overflow until it's below the threshold pressure, resulting in the noticed reduction. There should be a hose attached forcing any overflow to the ground away from the wheel, I wonder what you'd find if you attached a bag to this - like a reasonable strength large sandwich bag cable-tied to the end of the drain hose.

A leak in the heater core might also be noticed in the A/C drain pipe (front of the left hand passenger footwell in Australia). Normally you'd notice this on the ground, because unlike some cars that drain the A/C condensation onto the exhaust, the Navara doesn't seem to do this (mine doesn't, anyway).

There are other possibilities. The radiator is connected to the automatic transmission (because the auto uses a section of the radiator as a transmission oil cooler). I had external coolers fitted and the radiator connection removed to avoid contamination of the transmission fluid. If yours is an auto, check the oil in the gearbox to see if it's milky.

The coolant is also used to cool the turbocharger AND the EGR. Either of these could leak but are unlikely to be your problem because your losses stop at a certain point, but I'll still address them.

The EGR one is simple: get an appropriate piece of pipe to fit, and connect the two hoses that are on the EGR cooler (front of the engine) to each other, bypassing the EGR cooler. If the problem has gone, then the EGR cooler itself has a hole in it (internally) and coolant will be finding its way directly into the intake manifold (likely in small quantities that may not noticeably affect performance).

Identifying a problem in the turbocharger is harder. If coolant is making its way past the seals behind the turbine, it could be joining the exhaust stream where the coolant will be vaporised (typically see temps there of 500 celcius or higher). This will just head straight out the exhaust completely unseen. A gas analyser might spot the problem - a decent mechanic's workshop will have one of these. Again, I don't suspect this as a problem because this would continue draining the coolant.

Bag on the oerflow is a good idea, I'll try that. I've got a manual so that rules out the auto transmission. I am starting the suspect the heatcore again, I've got a big bash plate under the front end so if it's only a little bit at a time it could just be drying before finding its way to the groud? I just don't see why the level would stop dropping. I suspected it could be the turbo seals too because it's on its way out, but like you said it wouldn't stop dropping if it was something like that. I might pull the bash plate off for a week or two and see if I can notice any small puddles. Cheers for your help!

 

[fuzzylogic]

Small crack in the expansion tank? Is it pressurised when the system is hot?

 

[mrmeme1212]

Yeah the expansion tank is pressurised, so it could be that. I've heard they have had problems with them. I'm not sure how I can test that though.

 

[Old.Tony]

Yeah the expansion tank is pressurised, so it could be that. I've heard they have had problems with them. I'm not sure how I can test that though.

I had an expansion tank split along the horizontal seam. Spat everything out when hot, tank near empty once cold. I still have the tank in a box after buying another replacement, my intention is to plastic-weld this one so that it never leaks again.