Previa Engine Running Hotter

[stjoolzz]

Got a problem with my 96 Previa. It is running hotter than usual on some journeys (not connected with the very hot weather as such).

It will be fine for a while and then after 20 minutes or so it will slowly creep up.

If I put the heating on just a touch it does bring the temperature back down fairly quickly so that I have not let it actually overheat as such.

I have replaced the coolant (proper stuff as before) which has made no difference.

Could it be the thermostat?

I am driving to southern Brittany in 2 weeks time to need to make sure it is OK.

[Tardis]

It could be that the Thermostat isn't opening (at all, or early enough). You can either replace it since they're not expensive or take it out, drop it in a glass of very hot water and see if it opens.

I hope you've checked the obvious that there is water in the radiator, and it isn't just leaking water from somewhere.

Has anything changed? Has the airflow through the radiator been limited for some reason? Is the engine running OK? Is there water in the oil (brown sludge on oil dipstick or in radiator header tank)?

Good luck.

[stjoolzz]

Thanks

I completely drained the system but it ran clear though a little brown. The coolant was last changed 3 years ago.

I would have a go at the thermostat myself but all maintenance is done out on the street and I cannot get to it properly. I may have to book it into the garage.

[Tardis]

The water running a little brown isn't anything to worry about as long as you don't have the dreaded sludge (this indicates head gasket/warped head problems). The brown is a little rust but perfectly normal and not the cause of your high temperatures.

The other thing which can cause high temperatures is a blockage in the radiator/cooling system. There are purging agents available to clear the system but I wouldn't recommend these since they can make the problem worse by causing holes.

The thermostat would be a good next step. I have to admit I've not done this on the Previa but it's usually simple and therefore cheap - the thermostat housing is on the engine end of the top radiator hose, usually attatched by a huge allen key screw.