motopix

I just had my water pump replaced and a 160 thermostat installed. Car already had 3rd rad.

The water pump in there had a metal impeller, contrary to what I requested. Thankfully no damage to engine when it started to wobble.

I'm fairly confident the cooling system was in good shape before the new pump/thermostat as I alway ran 200-205 on the street and only got up to 225 at the one trackday I attended (temp in the 60s).

But now the car is running consistently 20-25degrees cooler and I don't really understand why.

Was the old thermo not staying open all the time?


edit: talking about oil temps here
edit2: subject edit to specify oil temps

Lvt19672

That's not good, oil temps might not get hot enough now.

motopix

175 degrees is not hot enough? If you're thinking because of water accumulating in the oil, the car has been running for 3 years at 200-205 oil temp and 4-5 Blackstone tests never found water in the oil.

Or are you thinking of another reason that could be a problem?

Lvt19672

The boiling point of water is 212 deg F, if your oil temps are 200 deg F, you haven't reached the boiling point yet. Someone correct me if I'm wrong.

motopix

Yes, I addressed that above. According to my oil temp gauge I was never above 205 degrees on the street for the past 3 yrs and never had water in the oil when it was tested.

Fahrer

One does not need to reach 212 to drive water out of the oil. The amount of time the car is driven is more important. Oil at 170F for 8 hours will be drier than oil at 212F for 5 minutes. Ever bring a pot of water to boiling? It's still there and will take a while to boil off. People will dry their hair with a blow drier and their hair does not reach 212F. It's accelerated vaporization.

It's important to get the oil temp up to 200F+ before high revs and high loads but to get the water out of the oil from a cold startup, one should drive for at least 45 minutes to an hour. It just happens that the oil temp will exceed 200F during that time but if it were 170F for one hour the oil would dry.

Fahrer

The oil is cooled by the cooling system. This is probably why you see the lower oil temp, given the lower temp of the cooling media with the lower the thermostat ( or actually the water pump is now pumping adequately?).

Appraiser

Moto - I did a 3rd rad with bumper cutouts, 160 temp thermostat, new water pump and full coolant flush in the summer. I had a similar experience, about a 20 degree drop across the board consistently. Before the change I would maintain 215 on regular cruising and spike at 250 on the track (100 degree day) and would spike 230-235 on spirited drives (90+ degree days and nights). Now I'm steady cruising at 195-200 degrees regularly with spikes to 215-220 on spirited drives and around 230 on track with a/c on (92 degree). Long uphills accelerate the needle. When I'm driving in sub 75 degree weather the temps barely want to crack 190 and I hate how long it takes for the car to warm up. I suspect the extra rad volume is pulling the heat away from the engine more so than anything else. I've been told our cars are good up to 260-270, then you'll want to pit or cruise for a cool down.

user 72902

As a reference point I’ve had 160 thermostat longer than I can remember and send my oil samples out for testing. Reports never show water or fuel in the sample.

docdrs

So , I am assuming you had a 180 tstat before and now you have a 160. Why would you not think things would be 20 degrees cooler? Maybe I am being to simplistic, but the cooling system is doing what it was designed to do.

If you had a 160 before, then you should check it in water to see if it was starting to open at 160.
If it was then maybe your water pump was sub par and the new one is more efficient. Kind of hard to discuss without knowing what your original tstat was.

bdiamond001

Just replaced water pump. I'll be interested to see oil temp. Oil temp has seemed high in city driving.
Great information on this site.

motopix

You make good points. Old tstat was standard temp. I kept it and will test it sometime.

As for why surprised: I guess I assumed the old thermostat was open all the time. But you're right that is obviously not the case.

vern1

A 160 tstat does not make the car (or any car) run cooler. It only determines when it opens

motopix

I drive 24 miles each way to work and since the tstat and pump change have not gotten oil temps over 185. It would have been 200-205 prior.

So you would attribute the temp change to?

Appraiser

Agreed it's the coolant that takes the heat away and if the port is opening sooner, presumably in cool ambient weather where the poster is, the oil temps wouldn't have the time to reach previous peaks but it wouldn't be a 20 degree flat difference... At least it doesn't make sense on paper that it would - rather it would increase the time for the original engine to get to that point. Now the debate is how long?

Maybe a higher functioning water pump? If the total efficiency of the cooling system is operating sooner preventing temperatures from rising as quickly, then the lower temp t-stat would be doing its job. We need a thermodynamicist to come in and drop some knowledge on us. My thinking is a hotter total [180+] system takes a lot more (non-linear) effort for the cooling system to keep in check than a cooler total [160+] system which would be a time factor that you aren't seeing. If I have my car idle for a while to let the oil circulate I'll see 200-205 degree temps. It gets there, it just takes forever. What do you get when you idle for a period of time?

Porsche already filled the system with a good amount of coolant. Maybe with the added coolant capacity there is an in-balance between radiant coolant potential and exposure (negative) vs heat generation (positive) for most driving conditions with the t-stat and rad combo. Which we wouldn't want outside of a race track ala GT3/X51/etc. I'm not saying Porsche had the system figured out to a a thousandth of a degree but I bet it was a robust setup capacity vs heat for all types of weather and driving conditions.

Is your ambient temperature changing as well? I see 5-10 degree average changes for every 20-30 degree outside temperature change for most cruising.