'96 TDI is running too cold

Just started to run cold for some reason. It normally shows 180/190 F, now it won't get hotter than 150F even at 75 MPH. Once I slow down in town ( 30 miles away) it will go to 190 and stay there the rest of the drive,even the 75 MPH drive back home.
Any ideas?

A quickie check is your top radiator hose vs bottom to see if thermostat stuck open. Should show great difference during cold start then even out if thermostat opens.

If you begin fairly even then may be stuck open.

If you don't have a temp gun you can use hand touch but of course be careful and all that

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You may also be able to see if a pending fault and freeze frame showing a crazy reading for ECT

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thermostat, probably.

Mongler98 said:

thermostat, probably.

Click to expand...

X 2, Buy a 195 degree thermostat.

Your thermostat has become lazy

Thanks for the replys. now I need to find which maker brands are worth a darn.

I would go OE on this one - it's a pain to replace, and you should think about getting the plastic elbow under it - they get brittle with age

plastic thermo-housing/elbo isnt expensive. i tend to replace mine everytime i do a water pump. ie when i do a timing belt. its plastic, its smart.
id suggest the stock temp of 87C (thermo), as someone suggested a hotter replacement.
new coolant?
if not^ when i drop mine, i drop in a clean coolant pan. it gets road dirt and oil in it. i take a empty coolant jug and a funnel, take a bounty paper towel, double it over and use in funnel as a filter. make sure no openings betw towel and funnel on sides. filter works for me, as far as usable coolant, thats not too dirty from the pan. after check what you filtered/recovered, its 'clear' (its red of course), no oil film on top.

Use a clean shopvac and suck up the coolant as its coming out of the hose, no mess no fuss, and if its good, you can reuse it.

I’ve had good luck with, Stant 45379.

-Todd

This sounds like a thermostat stuck open to me.