Hey guys, I am not sure if this is normal but whenever i hit the highway my engine temp seems to dip about a third below the mid point. The temp rises back to normal whenever i stop the car at traffic lights. I just got a new radiator and I do not seem to have this problem when I am driving in the city. I am worried that the fluctuation of the temperature might be bad for the engine especially the head gaskets since the metal is contracting and expanding all the time especially when it is really cold.

personally i dont have this issue with mine, but if you have concerns try taking it back to the guys who supplied / fitted the new radiator and ask them to double check everything,

cant hurt to check your thermostat is working properly either

Sounds a bit odd, but rest assured the water temp fluctuating from normal to cool won't damage the engine in that way, it's only coolant maybe 10-15 degrees between those two points. Engine blocks and head run far hotter than that as oil temps typically do

Typical thermostat issue, thermostate is staying open thus too much flow thus engine is runing too cool

this also effect fuel consumption: getting worse mileage. My Verada used to do this, and it was the thermostat. Except mine would not overheat in the city but on the highway it would dip to cold start temp. Not good.

My TR would only dip a little under half temp on cold mornings, then the toptank hose neck broke off and i had it flushed and a new tank fitted. Now in winter, coasting down a hill at 80 for about 2 mins the temp drops to about 1/3. (also have heater on at the same time).

this also effect fuel consumption: getting worse mileage. My Verada used to do this, and it was the thermostat. Except mine would not overheat in the city but on the highway it would dip to cold start temp. Not good.

So did you fix the thermo? was everything all right after that?

Thermostat is stuck open. Get a new one and stick it in.
I replaced the thermostat on our other car (4 pot Toyota FWD) - two bolts on the thermostat housing, a bit of coolant spilled onto the driveway, remove & replace thermostat, reattach housing and 2 bolts.

I screwed up an oil change, but the thermostat swap was a piece of cake. 5 minutes tops.
Not sure where it is on the Magna though, could be as hard as changing plugs on the rear bank for all I know so far. Anyone want to tell us where the thermostat is and if it's a noddy replacement or best to tach to a mechanic for the less mechanically able peeps like me?

Cheers, Graham.

well if the TS's 2.6 is the same as my TNs then you want to follow the top hose back to the engine and its just there. 2 bolts to remove, i cant remember if it was a 10mm (or perhaps it was 12mm) socket. I used an extension bar as it was a little tricky to get to what with the fuel rail being right there.

I had the same problem as you guys and my thermostat was rusted fully open so that when i was bringing it home on the fwy it went back to stone cold, like Lynel's.

Easy fix and the good feeling that there was a problem and i fixed it! Previous car only really had one problem, a cracked head/gasket, and i couldnt really fix that myself.

Hey guys, I am not sure if this is normal but whenever i hit the highway my engine temp seems to dip about a third below the mid point. The temp rises back to normal whenever i stop the car at traffic lights. I just got a new radiator and I do not seem to have this problem when I am driving in the city. I am worried that the fluctuation of the temperature might be bad for the engine especially the head gaskets since the metal is contracting and expanding all the time especially when it is really cold.

Experienced this very effect when the radiator was replaced in my old EA Falcon; the new radiator was much more effective than the original one and the original thermostat was opening at too cold a temperature (gauge would only just get to the bottom of the normal band, no matter what I did). Had a thermostat with a higher opening temperature fitted and problem sorted. With new thermostat, the gauge did fluctuate a little bit more noticeably, but it was around the middle of the normal range and not that much of a fluctuation so I let it go at that.

Whether changing to a thermostat with a slightly higher opening temperature is actually worthwhile in your case I'm not qualified to answer.

Andy.

Ok got a new thermo and got my mech to pop it it. He charged me 50 dollars including the new thermo. Is that too expensive?

from memory my thermostat cost about $20 from supercheap, so $30 for a mechanics time isn't too bad.

But please tell us that the problem is fixed now! ???

edit: double post, but I did NOT press submit button more than once.

Was $40 for my replacement thermo (DIY)... Took 10 mins and a fluid flush to install. Excellent deal!

from memory my thermostat cost about $20 from supercheap, so $30 for a mechanics time isn't too bad.

But please tell us that the problem is fixed now! ???

Have yet to test it on a highway. But the car seems to be heating up faster. Seems like everything is back to normal.