joecar

Ok, so the coolant flowing like this is bypassing the thermostat, I think I understand it a little better now.

I'm consistently seeing P0128 (and absurdly low running temperature) on a 2002 GAGT 3.4L LA1, it has a closed system (so both issue and curious).

Thanks.

AnotherWs6

iTrader: (17)

You got it. So the big question...... has the radiator ever been replaced?

joecar

Doesn't look like it... but the hose from the radiator to the surge tank has been replaced... I'll pull it and inspect the inside of the hose and the port on the radiator.

[ Also, I saw today the surge tank has an otherwise invisible hairline crack at the top... this is so much fun... ]

Russ K

iTrader: (1)

I can't find a TSB for your car. If the engine doesn't reach 176*F within a certain time, then the P0128 will set. Did you try replacing the thermostat?

Russ Kemp

joecar

TS is a bitch to get to on this car (exhaust manifold has to come off), but I'll have to do it.

Russ K

iTrader: (1)

You can do it without removing the cross-over pipe. At my shop, we remove the throttle body to gain enough room to change the stat. It's a tight fit.

Russ Kemp

joecar

Ok, thanks for the tip, I'll try that.

AnotherWs6

iTrader: (17)

I am no mechanic, but I'll throw my logic your way. See if it makes sense.

The car is running cool (and we are assuming that this is true and that you dont have a bad sensor - does the car produce good, hot heat?) because too much coolant is being allowed to flow through the rad and back into the motor before it has a chance to warm up. There are two possible places this could happen. 1 - The thermostat if it is stuck open. 2 - The bypass hose from the surge tank to the water pump. Assuming that this is correct, and since you said it looked like the tank was replaced, I think it makes more sense to rule out number 2 first. It seems not only more likely that the problem is here but also easier to check than getting to the thermostat.

Alluding to what another member mentioned here..... Can you see through the surge tank? I recall now (yes I saw this and thought nothing of it months ago) being able to see a lot of coolant flowing into the surge tank coming from the line connected to the rad. In hind sight it was like A LOT!!! If you can't see though it you could always just pop the line off of the surge tank and have someone start the car. If coolant comes pouring out then I would think that that is your problem.

joecar

Ok, thanks, your idea has been noted (it is very simple to do).