Just got my '98, 6 spd, 52k miles coolant system flushed and had replaced all cooling system and heater hoses, thermostat (stock for stock I assume) since they were 14 years old. (had it flushed before 5 years and 30k miles ago). Had it done by a local dealer.
After taking it home next day noticed a silver dollar size coolant stain on garage floor so took it back. It leaked at the thermostat "o"ring. They replaced the "o" ring and no more leaks anywhere however I'd like to share with you a few things after I took the car for a test drive in the streets and freeway. Time was 9 PM, 54F outside, freeway and streets no traffic, flat road on both freeway and streets.

1. On freeway temperature read would fluctuate between 196-198F at 75 mph on 5th gear. Steady pressure on gas pedal.

2. On freeway if going at the same speed 75 mph on 6th gear temperature would rise to 205-207F and stay there. If down shift to 5th gear temp will lower again to 198F

3. At idle car would heat up to 225-227F then cool off to about 210F after fans kick in.

I'd like to know your opinion on both 1., 2. and 3. if you think those operating temperatures are normal, and why the temperature would rise when swiching gear (from 5th to 6th) Same road conditions, same speed of driving same temperature outside. I thought that lower revs in 6th gear would make the engine run cooler but...??
Your input is greatly appreciated and please try to answer to all questions separate.
Cheers

 

I'm no expert, but would assume the cooler temp, in a lower gear, with higher rpms, is due to the water pump flowing more water since its spinning faster.

I do know my 99 will hit about 228, then drop to about 210 at idle. This is only on days with lots of driving, starting and stopping. Usually on days I drive to work, it never goes above 190, but I only drive 20 miles round trip.

On the freeway, it runs about 185.

 

Mike, are you reading those numbers rom the analog gauge or from the elecronic display ? I think is hard to read from analog. I read from electronic display

 

swiching gear (from 5th to 6th) Same road conditions, same speed of driving same temperature outside. I thought that lower revs in 6th gear would make the engine run cooler but...??
Your input is greatly appreciated and please try to answer to all questions separate.

The reason this occours is both 5th & 6th are overdrive gears so when you go into 6th gear you do reduce the RPM's but you put more load on the engine thus driving the temp higher.

 

so 196-198F are OK temperatures given the road conditions I described?

 

Stock themo is at 195*
Stock fan settings are
#1 on at 226 off at 219
#2 on at 235 off at 227
#1 fan turns OFF at 35 MPH or higher
#1 fan comes back ON below 30 MPH
Huge aamount of opinions on this stock set up
My opinion would be to run it differently and has proven to be very successful
Thermo 160*
#1 on at 190 #1 off at 185
#2 on at 197 #2 off at 191
Set #1 fan MPH settings to MAX setting ( 256) so it comes on/off soley by temperature and not MPH
My A4 car runs about 185* all the time --The hottest it gets say like on a hot day around town is 195* Even with a 3000 stall---

 

are they ok?

 

anyone?

 

Can running the lower temperature thermostat throw any codes? I'm thinking of going to a 160 and have not had a tune. Would this lower temp thermostat cause any problems? and would it help drop the running temperature?

 

what temps do you get on the freeway this time a year ?.....lets say 65F outside and you would go 75 mph on the 5th gear....also what temps on 6th at same road conditions?

 

I have a 98 A4 that is modded and i run a 186 TS. My car runs around 198 degrees. Before the mods and the stock TS my car temps ran in the low 210-220. I was told that and have read that the LS engines run hot by design and has something to do with heating the oil to a certain tempt etc. I'm by no means a expert but do a search in this section on TEMPS and there is a really good thread on TS and temps. Some say the 160 TS is not good for our cars. Read the thread chose for yourself what you like and what's best for your car. It's along read but some good info.

 

My 98 with Vararam, under drive pulley and Headers wouldn't run over 195 on a 54C day in 6th gear at highway speeds from say 55mph to 75mph. I'd never run in 5th at those speeds unless accelerating or passing so I can't say what temps I'd see but I doubt they'd be much different.

Did you check the condensor and radiator for blocked fins?

 

Just had radiator flushed, new hoses and new stock thermostat...before I dont remember car doing that (206F on 6th gear)....had the work done here at a local dealer...what could they have done? I know thermostat controls the lower temps so could that thermostat be the culprit anyways?...or an air buble?

 

Would this lower temp thermostat cause any problems?
" If you drive the car in very cold temps ( below 35 degrees) you will NOT like the gas mileage or the hesitation you will experience. I'm speaking from experience."


WHAT ??? so you're saying a lower thermo (160-180) will affect gas mileage at 35* outside temps ?? How can that be when a stock 195 would be closed the same as a 160 would be at 35* ??? makes NO sense-----

 

Yes. Absolutely. No doubt. They are fine. You have no problem based on just those temperatures. They are normal. They are running as they should in stock form.

 

My car goes into closed loop WAY under 160 degrees......

I've yet to see a stock tune that has the minimum closed loop temperature set so high that a thermostat change would not allow closed loop either.

 

bob, does your car runs hotter in 6th too?

 

I have an A4.

 

trippy, i have literally, to the degree, the same settings with a 160 thermostat.

i also added some water wetter. with the latest addition of a halltech tunnel port, I've seen cruising oil temps hit mid-low 170's for the first time ever. they usually cruised around 190 even in dead of winter. summer may tell a different story, but so far my IAT and oil temps have dropped. RPM stage 5 A4.


yea.. although what 8vetteZ said is dead on if its true, i havent seen it. i havent looked @ what my closed loop temp is (i didnt change it, so its default i assume) but i havent experienced the above at all. maybe its cus im a ***** in cold temps and always let the car warm up before driving, but i havent had any winter issues. with 160 tstat & fans @ 190.

 

The typical minimum temp settings I've seen for closed loop are around 100F give or take. I even just looked up a few TBI and LT1 tunes. It's way below what a thermostat change would do, even going to a 160F one. I've read that arguement many times but not once was it backed with evidence from a tune.