Have been having a certain amount of coolant to overflow, and with time need to top off the coolant (maybe a half liter per week). Also a lot of brown particles in the coolant. Hoses are all fine, water pump is fine, radiator is fine. Temp gauge also sort of bounces up and down, never steady. A friend suggested it may be the head/head gasket. There's no water in the oil though. I hate to tear into it unless it's certain. Any theories out there in ThaiVisa land?

2001 Mazda Fighter 4wd.

First thing buy a new radiator cap ... You don't need to pay Mazda price either.

That's kinda what I was thinking too. You think maybe a higher pressure cap? The one on there now is 1.1 (pounds?), and the local shop only had stuff lower than that, 0.5 I think. But a radiator cap would certainly be cheap fix.

I would suggest a new thermostat too..

I would suggest a new thermostat too..

And somebody who understands motors well enough. Would the head gasket be the problem, you'd defiantly see white smoke coming out of your exhaust system.

The thermometer "bouncing up and down" could also show a non functioning sensor.

P.S. You can'r just always fill in more and more coolant, it has to be a mixture of water and coolant.

Most vehicles will lose a little coolant over time due to evaporation from the reservoir. But a significant loss of coolant in a relatively short period of time usually signals a leak, a radiator cap that is not holding pressure or a cooling system that is running too hot. Visually inspect the radiator, water pump, hoses, freeze plugs, etc. for external leaks, and then pressure test the radiator and cap to find out where the coolant is going. A tight system should hold the maximum rated pressure for at least two minutes with no drop in the gauge reading.

Please see: http://www.aa1car.com/library/us50230.htm

That's kinda what I was thinking too. You think maybe a higher pressure cap? The one on there now is 1.1 (pounds?), and the local shop only had stuff lower than that, 0.5 I think. But a radiator cap would certainly be cheap fix.

No, put the same one on as now ... I had to get one for an old Mazda, I was amazed at their price ... I asked the local garage to get me one ... about 100Baht I think. What you could do is look at the overflow bottle (or what ever you like to call it) as soon as you switch off the engine when it's hot and see if its water level rises a lot ... also look to see if it looks like that bottle has overflowed.

If the cap doesn't sort it then do as others suggest. Last job is head off.

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It sounds like the radiator needs flushing out..sounds like the radiator volume has decreased internally..just my humble opinion

Thanks for the replies. Will pick up a new cap and thermostat. Would much prefer to Easter egg the little stuff than pull the head.

Thanks for the replies. Will pick up a new cap and thermostat. Would much prefer to Easter egg the little stuff than pull the head.

Is white smoke coming out of your muffler? If not, then it's not the head.

Thanks for the replies. Will pick up a new cap and thermostat. Would much prefer to Easter egg the little stuff than pull the head.

While at the auto parts store buy 80 bahts worth of cooling system sealer and bung that in.

Is white smoke coming out of your muffler? If not, then it's not the head.

Not entirely true,

depending which part of the head gasket is leaking.

A water way leaking in to the combustion chamber will cause white smoke from

the exhaust.

An oil gallery leaking in to the combustion chamber will cause blue smoke from

the exhaust.

A water way leaking in to an oil gallery will contaminate the engine oil.

An oil gallery leaking in to a water way will contaminate the engine coolant.

Is white smoke coming out of your muffler? If not, then it's not the head.

Not entirely true,

depending which part of the head gasket is leaking.

A water way leaking in to the combustion chamber will cause white smoke from

the exhaust.

An oil gallery leaking in to the combustion chamber will cause blue smoke from

the exhaust.

A water way leaking in to an oil gallery will contaminate the engine oil.

An oil gallery leaking in to a water way will contaminate the engine coolant.

And, condensation (water) in the mufflers will produce white "smoke" for a while on start up....

Well, I don't have any of those. No oil in the coolant, nor coolant in the oil. Nor white or blue smoke. Still haven't replaced the cap and thermostat, but will next time there's an auto parts store handy.