5sfe Excessive Cooling

[Snowfork]

I had a customer come to me with a problem today.

He has a Camry with a 5sfe in it and right after he changed the coolant, the symptoms started.
The temp gauge now rises normally as the engine warms up, but at highway speeds, the gauge decreases as if the radiator is shedding more heat than the engine is producing. I know it is **** near impossible for the coolant to cool at a faster rate than the engine is producing heat. He has replaced the thermostat in an attempt to fix the issue.

So what do you guys think is causing the issue?

[Snowfork]

I think it is the temp sender messing up, but I don't want to keep telling him to throw parts at the car.

[BottleCapBandit]

thermostat could be stuck open.

or the sending unit as you said.

[BottleCapBandit]

Good to see there are actually techs and other mechanics on this site.

[BottleCapBandit]

and not to post so many times but the heat would be affected if it was cooling to much. You could get him to warm the car up and then cool it down with driving and see if the heat is affected. Now that I think about you post I realize that you said it happens at highway speed which tells me the rad is over cooling. The only conclusion would be a faulty thermostat.

[BottleCapBandit]

**** I should read more of the post. Im stupid haha. But I dont think anything else can cause overcooling.

[Snowfork]

I told him that his heat would falter if the coolant was truly overcooling.
He replaced the thermostat already and insists on doing everything himself.
I am going to advise him to replace the sender then tell him that is all I know/can do for him. He won't pay to have a tech look at his car and keeps holding me up at work while he picks my brain.
I am a very nice guy in person, but he is costing me money.

[BottleCapBandit]

I completely agree. Im a cool dude but some people push me to the point where I have to tell them that I have work to be done. I know the type of person you are referring to. In the haynes book it states the only 2 reasons for overcooling is the 2 above. I wonder if he used gasket maker and gummed the new thermostat up. I would tell him to get another thermostat and sending unit. That will cover it.

Or installed it backwards... and yes. I have seen this before. They werent overcooling but it sure was in there backwards. haha

[Snowfork]

The issue occurred before he replaced the thermostat.
He shows indications of not knowing more than most primitive repair knowledge, but insists on doing every single repair himself. I had to explain RTV to him.

[BottleCapBandit]

Originally Posted by Snowfork

I had to explain RTV to him.

haha