Adjusted internal pressure, runs hotter?

[blackbird82]

Hey just so you know its a 1.9 td in a 94 aaz jetta
I adjusted my IP internal pressure and yes that made a difference! back to high 40's mpg!
I did a water pump shortly after and installed a new thermo from VW at the same time
Runs good, but when I push the car aka 130kmh or 160kmh, she climbs in temp to between the middle and 3/4 mark.
Never used to really used to hang on to the middle no problem
Any thoughts?
I am thinking I got a bad 35 dollar thermostat from VW
pricks

[the caveman]

Be careful while trying to figure out your problem .Do one thing at a time. I would think more along the lines of thermostat etc.
BUT my pal Steve [ very very smart guy] has an AAZ in his Vanagon. He went though years of trying to figure out why his engine was running very hot when pushed. He replaced the head that we knew was good, then I found him a good block. Same thing. Last year he was stuck for a couple of days on his way back from Labrador and decided to check his pump pressure. I had it rebuilt for him, but was never put on a bench to test. Ran fine but he had his gauge with him so.... Anyways he adjusted the internal pressure [sorry don't know up or down] and his overheating problems disappeared immediately.

[burn_your_money]

If you think it is too much internal pressure then just retard the pump timing a bit

[blackbird82]

interesting. before i think it my pressure thats doin it. I am gonna rule out all cooling system stuff.
i know the pump is good, flows wicked, good return to tank and flow to heater core
gonna make sure t-stat is good. and the rad is 17 years old. maybe take it off and give a vinegar bath.

[smutts]

I don't know if this helps, but the first time I adjusted the internal pressure on one of my GTD's I overdid it a bit. You could hear an odd combustion rattle at driving speed, not quite marbles on a glass plate, but I didn't like it and adjusted the pump timing back to the standard setting. When I changed the injectors for new ones a few months later, the nozzles were tempered a straw colour, so had got too hot. But this shouldn't show as a hot gauge. More than 50% antifreeze can make things too hot too. Both  my GTD's run at 5/8th's of the temp guage, and don't move from there despite whatever the abuse.
Possibly the new timing has increased the peak combustion pressure in the cylinders, if this is causing a weak cylinder gasket to seep bubbles into the coolant, that can also cause hotter running. See if the radiator hoses are still rock hard after the car has sat for an hour. If the radiator cap is good and the head isn,t. Hard hoses await. Happy hunting.