Weird higher temperature after water pump and thermostat change - why?

[jchapura]

2005 C2S ~52k miles

 

For the record, for multiple months prior to these maintenance procedures, I noted an oil temperature of about 205 deg F, whether the ambient temperature was warm or cold. I could get the temp to go up by keeping the RPMs above 3000 for an extended time. Most of the time the needle just stayed pretty steady at 205.

 

The one day, saw leaking coolant from underneath the water pump. Decided to change the water pump and thermostat myself. I also changed some of the hoses that touch other about-to-be-changed-out parts. I changed the reservoir cap. The new thermostat was labelled as "71" and marked Motorad. I have no history of whether any prior coolant system work had been done by others.

 

When initially draining the coolant, I used the AirLift three additional times to pull fluid to the back end of the car to get a more empty system. Then I did the parts change out. Put everything back together. The system held its vacuum for at least five minutes. I then refilled with straight distilled water, intending to "flush" out the old, yellow-ish coolant since my new coolant was Audi G12 anti-gel "red". I took it for a 15 minute spin to mix up, and heat up, everything. I drained the diluted coolant three time with AirLifts in between.

 

It held vacuum again. Proceeded to add 3.3 gallons of straight G12 since that's what I calculated I needed (for appropriately 50/50 against a total capacity of 8.6 gallons). Finished/topped off with distilled water.

 

To try to get any potentially trapped air pockets out, I turned the heater on HI and fan on high. I'm now getting about 212-215 oil temperature and the needle seems to move (up and down) more often compared to the pre-change state.

 

I was really hoping for a reduction in oil temperature after the change-out because of the low temperature thermostat. What might explain why the "reduction" seems to have gone the other way?

 

Thanks for any insights you might provide.

 

 

 

PS: The bright side - there's no more leaking coolant. [Although I didn't hear much noise from the old water pump - when I had it on the bench I could tell the bearing was shot.]

[wizard]

You might try 'burping' the system.

Does Porsche coolant (yellowy/green) and Audi G12 'mix' without potential gelling?

[jchapura]

I will look up how to "burp" with Porsche system - not really sure what that entails. (Was really hoping that the Airlift would have eliminated this burping step. Oh well.)

 

According to the source of the Audi G12 I bought, they are compatible and essentially the same chemically, just different colors.

[JFP in PA]

 

2005 C2S ~52k miles

 

For the record, for multiple months prior to these maintenance procedures, I noted an oil temperature of about 205 deg F, whether the ambient temperature was warm or cold. I could get the temp to go up by keeping the RPMs above 3000 for an extended time. Most of the time the needle just stayed pretty steady at 205.

 

The one day, saw leaking coolant from underneath the water pump. Decided to change the water pump and thermostat myself. I also changed some of the hoses that touch other about-to-be-changed-out parts. I changed the reservoir cap. The new thermostat was labelled as "71" and marked Motorad. I have no history of whether any prior coolant system work had been done by others.

 

When initially draining the coolant, I used the AirLift three additional times to pull fluid to the back end of the car to get a more empty system. Then I did the parts change out. Put everything back together. The system held its vacuum for at least five minutes. I then refilled with straight distilled water, intending to "flush" out the old, yellow-ish coolant since my new coolant was Audi G12 anti-gel "red". I took it for a 15 minute spin to mix up, and heat up, everything. I drained the diluted coolant three time with AirLifts in between.

 

It held vacuum again. Proceeded to add 3.3 gallons of straight G12 since that's what I calculated I needed (for appropriately 50/50 against a total capacity of 8.6 gallons). Finished/topped off with distilled water.

 

To try to get any potentially trapped air pockets out, I turned the heater on HI and fan on high. I'm now getting about 212-215 oil temperature and the needle seems to move (up and down) more often compared to the pre-change state.

 

I was really hoping for a reduction in oil temperature after the change-out because of the low temperature thermostat. What might explain why the "reduction" seems to have gone the other way?

 

Thanks for any insights you might provide.

 

 

 

PS: The bright side - there's no more leaking coolant. [Although I didn't hear much noise from the old water pump - when I had it on the bench I could tell the bearing was shot.]

 

 

The two issues (car running hot and the water pump leaking) may not necessarily be related.  We have had cars come into the shop that had the water pump, coolant, and thermostats replaced, but still ran hot.  When we pulled the front bumper cover off, enough trash fell out to fill a waste paper bin.  After the radiators were cleaned of junk, the car was fine.

 

And a couple of "by-the-by's", never add pure coolant to the car, always pre dilute it with distilled water first.  It may take much longer than you think for the system to reach a 50/50 dilution.  If used properly, no burping should be needed when using the Uview system, that is why the tool exists.

[jchapura]

The two issues (car running hot and the water pump leaking) may not necessarily be related.  We have had cars come into the shop that had the water pump, coolant, and thermostats replaced, but still ran hot.  When we pulled the front bumper cover off, enough trash fell out to fill a waste paper bin.  After the radiators were cleaned of junk, the car was fine.

 

And a couple of "by-the-by's", never add pure coolant to the car, always pre dilute it with distilled water first.  It may take much longer than you think for the system to reach a 50/50 dilution.  If used properly, no burping should be needed when using the Uview system, that is why the tool exists.

 

Thanks JFP. I wish I had known about the "pre-mix" rule. Mea culpa. When you say "much longer", how many operational minutes or hours are we talking about?

 

Tell me though, what might explain the change in relatively steady state oil temperature of 205 (pre) to 215 (post)? I definitely have heard of the radiators getting "trashed in" but mine are the same trashiness (from before the new pump and tstat, and after)?

[JFP in PA]

 

The two issues (car running hot and the water pump leaking) may not necessarily be related.  We have had cars come into the shop that had the water pump, coolant, and thermostats replaced, but still ran hot.  When we pulled the front bumper cover off, enough trash fell out to fill a waste paper bin.  After the radiators were cleaned of junk, the car was fine.

 

And a couple of "by-the-by's", never add pure coolant to the car, always pre dilute it with distilled water first.  It may take much longer than you think for the system to reach a 50/50 dilution.  If used properly, no burping should be needed when using the Uview system, that is why the tool exists.

 

Thanks JFP. I wish I had known about the "pre-mix" rule. Mea culpa. When you say "much longer", how many operational minutes or hours are we talking about?

 

Tell me though, what might explain the change in relatively steady state oil temperature of 205 (pre) to 215 (post)? I definitely have heard of the radiators getting "trashed in" but mine are the same trashiness (from before the new pump and tstat, and after)?

 

 

It could take a couple of hours of running before it reaches equilibrium.

 

Could be an air pocket, or lower heat transfer because the system is not completely mixed. 

[jchapura]

Does this coolant heat up chart look like it's from a car with a low temperature thermostat?

 

 

[JFP in PA]

Does this coolant heat up chart look like it's from a car with a low temperature thermostat?

 

It looks slightly warm, but not by a lot.  I would expect a car with the 160 stat and an otherwise clean cooling system to run 175-185F on a stead state run (copious air flow over the radiators) in 68F ambient temperatures (you also did not mention your ambient during your test).  The same car with the factory stat would run 205-215F under similar conditions.

[jchapura]

It looks slightly warm, but not by a lot.  I would expect a car with the 160 stat and an otherwise clean cooling system to run 175-185F on a stead state run (copious air flow over the radiators) in 68F ambient temperatures (you also did not mention your ambient during your test).  The same car with the factory stat would run 205-215F under similar conditions.

My ambient was about 65 deg F for yesterday's run.

Here's this morning's chart (60 deg F ambient; same route; but one longer episode of stop-n-go traffic) with car speed (to suggest that there is sufficient radiator air flow).

 

I'm not convinced the tstat is the low temp variety or not defective. Of course, i'm trying to avoid cracking open the coolant system again to replace it - hence my dilemma. But I will because I want the added engine protection of the lower tstat set point.

 

Is there a "poor man's" way to check the density of my coolant mix? Hydrometer's are not that expensive but was wondering it there's way to compare perfectly mixed brand new 50/50 with a sample from the car...

 

[JFP in PA]

 

It looks slightly warm, but not by a lot.  I would expect a car with the 160 stat and an otherwise clean cooling system to run 175-185F on a stead state run (copious air flow over the radiators) in 68F ambient temperatures (you also did not mention your ambient during your test).  The same car with the factory stat would run 205-215F under similar conditions.

My ambient was about 65 deg F for yesterday's run.

Here's this morning's chart (60 deg F ambient; same route; but one longer episode of stop-n-go traffic) with car speed (to suggest that there is sufficient radiator air flow).

 

I'm not convinced the tstat is the low temp variety or not defective. Of course, i'm trying to avoid cracking open the coolant system again to replace it - hence my dilemma. But I will because I want the added engine protection of the lower tstat set point.

 

Is there a "poor man's" way to check the density of my coolant mix? Hydrometer's are not that expensive but was wondering it there's way to compare perfectly mixed brand new 50/50 with a sample from the car...

 

 

I would say yes, for the simple reason that the OEM stat does not start to open until 186F and is not fully open until around 205F; your system is trying to stay below that.

 

A 50/50 mix of distilled water and coolant should have a specific gravity around 1.07, and a freezing point below -35F.  You could check the SG using a battery hydrometer, just be sure to clean it out thoroughly before using it on a battery again.  You could also check the freeze point using a readily available coolant tester:

 

 

[jchapura]

This past weekend I changed out the new thermostat that was giving me even warmer oil temperatures than the original regular temp thermostat.

 

The new low temperature thermostat acted like I expected to. It gave me oil temps about 8 deg F cooler than the original regular temp tstat. The first low temperature thermostat must have been a dud. Attached is an image of the old and new tstat coolant temp graphs clearly showing the approximate 20 degree difference in the temperature at the plateau (after warmup).

 

I did boil all the tstats - they did open pretty close to what I read should be expected.

 

I'm happy it's resolved. I hated to have to spend another half-day to change it out again. I'm hoping it does its job to protect the engine just that little bit more.

 

Thanks everyone for chiming in.