Originally Posted by superflyguy9
I would say EGR thermostat is working (opens around 70 degrees) - sounds like main stat has gone weak as that should stay closed until 90 degrees. I have read a lot of posts and thats how I understand it....I think
You can't look at it like that.
If the EGR stat isn't closing properly the it's not letting the flow of coolant be held at the main stat, it acts as a bypass route
So, again, the cheaper option is to replace the EGR stat first as it's cheaper (around £12) and an easy DIY as you won't lose any coolant) then if that stat change doesn't cure it replace the main one !