Thermosat Sticking?

[mullinsm]

Hi,

Having recently moved from a 981 Cayman S to a 991.2 Carrera 2, I was having a bit of a blast up a section of the new Norwich Northern Distributor road. On a warm engine, I had been driving quite hard in Sport mode for several miles when I noticed that the coolant temp had dropped to 75 degrees. I pulled off into a lay-by and waited a few minutes and the temp. came back up to 90 degrees and steadied off as normal. I set off again expecting it to fall once the air started flowing over the rad's again, but it's been fine ever since with no re-occurrence.

I've known thermostats to stick open before and even for them to do it intermittently, but I wouldn't have expected it on a car with under 6,000 miles and for it to happen just once seems a bit bizarre.

New to this forum and wanting to know if anyone else has encountered anything like this??

 

[ellism]

I had a serious cooling problem with my last 2S, which started just about a year ago. Periodically the temperature gauge would shoot up to maximum, the fan would be going like crazy, and I would get a warning to stop driving to avoid engine damage. Between July and November, it went back to Porsche 4 or 5 times to be fixed, whereupon I lost patience and told them to keep the car. Good news is that they ended up doing a deal with me which resulted in me getting my lovely new GTS in March this year (I had the use of a newish Boxster while I was waiting). Anyway, on picking up the GTS, I asked what had happened to my previous car and they told me it turned out to have been a water pump issue and it was now a recognised fault. So, although your problem seems the opposite of mine, I do think you should get in touch with your dealer and have them check it out. Could be related I suppose? Good luck

Cheers

 

[tscaptain]

I don't mean to be funny but it was the water temp you were looking at and not the oil? The oil temp runs cooler in Sport mode on the 991.

 

[mullinsm]

I don't mean to be funny but it was the water temp you were looking at and not the oil? The oil temp runs cooler in Sport mode on the 991.

No, definitely the coolant. It only took about a minute, maybe less, to get back up to temp. once I'd pulled over. I've read somewhere that the coolant is diverted to the oil coolers if the oil gets hot (and it probably was hotter than usual) so there may have been some sort of air-lock due to that happening, but not knowing enough about the routing of the cooling system and the placing of the stat I can't really say what it was. Hence the post....

 

[mullinsm]

Further to this issue, I noticed that the car seemed to be taking a long time to reach temperature after this happened. It takes about 8 to 10 miles of driving at normal speeds for the coolant to reach 90 degrees. I called my OPC and they said it sounded like a fault and picked the car up to investigate. Having tested the car they now say it’s fine and they would expect it to take this long to warm up. Anyone with a PDK 991.2 Carrera 2 like to give me a comparison?

 

[mullinsm]

Further to this issue, I noticed that the car seemed to be taking a long time to reach temperature after this happened. It takes about 8 to 10 miles of driving at normal speeds for the coolant to reach 90 degrees. I called my OPC and they said it sounded like a fault and picked the car up to investigate. Having tested the car they now say it’s fine and they would expect it to take this long to warm up. Anyone with a PDK 991.2 Carrera 2 like to give me a comparison?

I'll take that as a "no" then.....

 

[DandyDon]

I too have a 991.2 C2 Andy taking up to 8 miles to reach 90 is the norm. I’ve had it with all previous Porsche’s ( Boxster and Macan) and bigger engined BMW’s. It’s just the nature of performance engines and nothing to worry about. You’d have a problem if once you get to 90 it keeps rising. I’ve never had that problem.

 

[mullinsm]

I too have a 991.2 C2 Andy taking up to 8 miles to reach 90 is the norm. I’ve had it with all previous Porsche’s ( Boxster and Macan) and bigger engined BMW’s. It’s just the nature of performance engines and nothing to worry about. You’d have a problem if once you get to 90 it keeps rising. I’ve never had that problem.

Thanks for the reply, but I'm even more confused than before now! Before this car I had a 981s Cayman and, prior to that, a 987s Boxster. Both of those cars would hit 90 degrees about 2-2.5 miles into my daily trip to work. I also have a Mercedes c class estate and a BMW X1 (both diesels) that warm up in about the same time (perhaps a bit longer, but I would expect that, being diesels).

My local shop is just over 2 miles away down a long straight and, in my previous cars and this one until recently, I would drive there sedately as the engine wouldn't reach temperature but on the way back I could open the car up as it his 90 degrees just before I turned onto the straight.

Now, I can drive to work (approx 7 miles on A roads with a bit of traffic) and this morning the gauge showed 80 degrees as I pulled into the car park. Bearing in mind that the car is using more fuel than need be until the engine reaches operating temperature, quite apart from the extra wear on components, I find it amazing that Porches would design a car that took so long to hit operating temperature on purpose.

I understand that these cars have an advanced "intelligent" cooling system, but the basis of all car cooling systems that I've ever seen or worked on is that the engine coolant stays in the block until it reaches temperature and then the thermostat opens and allows the coolant to flow through the rest of the system. The whole point is to get to temp as quickly as possible and I can't see how not achieving this would be especially "intelligent" given the sacrifice in fuel consumption and engine wear that this would entail.

Are you sure yours takes 8 miles (approx 15 mins) for the coolant (not the oil) to hit 90?

 

[DandyDon]

I sympathise and agree with your comments that you’d think there would be some way to get to 90 more quickly especially with a car costing near to £100k. I’ve seen comments in various Porsche forums over the years saying the same thing. I always found the Boxster and now the 911 to be sluggish on colder days and noticed that the water temperature marches the outside temperature on the first start of the day so that in summer I’m up to 90 a lot more quickly but the opposite in the winter. I’ve now gotten fixated on the oil temperature gauge and find thatI’m reluctant to “go for it“ unless both are at 90/95 respectively. The forum chatter also seems to indicate that 4000 rpm is the maximum while you’re waiting for 90 and I find that that is giving me plenty of poke until all temperatures are ideal. maybe try that for a while and see if it works for you.

 

[mullinsm]

I sympathise and agree with your comments that you’d think there would be some way to get to 90 more quickly especially with a car costing near to £100k. I’ve seen comments in various Porsche forums over the years saying the same thing. I always found the Boxster and now the 911 to be sluggish on colder days and noticed that the water temperature marches the outside temperature on the first start of the day so that in summer I’m up to 90 a lot more quickly but the opposite in the winter. I’ve now gotten fixated on the oil temperature gauge and find thatI’m reluctant to “go for it“ unless both are at 90/95 respectively. The forum chatter also seems to indicate that 4000 rpm is the maximum while you’re waiting for 90 and I find that that is giving me plenty of poke until all temperatures are ideal. maybe try that for a while and see if it works for you.

The thing which was troubling me most was that this car had been warming up much more quickly than it now is, but this could simply be due to the very warm weather we'd been having during the summer (I bought the car in April) and now that it's starting from colder, it's taking longer to warm up. However, I still wouldn't be surprised to find that there's a valve stuck open somewhere and it's warming more than just the engine block from cold. According to that most unreliable of sources, the internet, there have been a lot of problems with the solenoids used on the 991, especially on the early cars and that could well cause such an issue. As my OPC are saying the car is fine and you seem to suggest yours is the same, I'll just accept the situation and, as you suggest, take it easy for the first 10 miles or so. Thanks for your help- much appreciated.

 

[richardfleming]

ref solenoid/heat-exchanger valves - mine barfed on my 991.1 - no heat from heater, engine fine, AC fine. The OPC fixed it under warranty (4yr old 991.1) and all is well. They told me it's a known problem and I think I saw something about it in the club magazine a while back - they're plastic valves and do fail. maybe related to your particular problem, maybe not - but certainly worth getting checked out at the OPC/dealer.

 

[mullinsm]

After (almost) convincing myself that the car was supposed to take an age to warm up and just accepting it, after posting the response above I took the car out on Saturday evening. It reached 90 degrees in less than 1 1/2 miles and my wife was sitting next to me so I know I wasn't hallucinating! About 2 miles later, the temp dropped down to 78 degrees and then took a further 5 miles to get back to 90.

On my drive to work this morning (7 miles) it climbed slowly and reached 80 as I parked in my car park.

Does anybody have any idea what's going on?

 

[DandyDon]

Sorry, I can’t provide an answer but my experience is that 7 miles to get to 80 is normal. I‘ve never seen 90 come up as soon as 1.5 miles so that in itself seems odd. For it to then fall to 78 is really unusual and may point to a problem with the thermostat as you first suspected or a sensor which provides data to the dashboard. Are the digital and analogue temperature readings the same?

 

[Lancerlot]

The time taken for an engine to reach its full working temperature is dependant upon the ambient conditions.

The car will take longer to warm up on the move due to the passage of air through the rads. slowing the process down. If you run the car whilst stationary until full working temp is achieved, this would likely dispel your concerns.

On the move, once coolant has reached the correct temp. the thermostat opens, increasing volume and flow, often resulting in a temporary fall before resuming at the correct level.

Me thinks you may be worrying unduly, but it's a simple task to have the thermostat tested/replaced in order to set your mind at rest.

Regards,

[font="comic sans ms,sans-serif"]Clive[/font]

 

[mullinsm]

The digital and analog gauges are both reading the same, so I doubt it's an issue with the gauge, although it could be a sender/sensor issue I suppose. The thermostat must be ok because, once it gets up to temperature on a longer run, it stays there without fail.

Reading the internet forums etc. there was (is?) clearly an issue with the solenoids used on early 991s as there are loads of posts from people who have had cooling system issues because of these switches failing. I can't find a schematic of the cooling system anywhere but from what I can gather, aside from the thermostat, there are other valves which open to allow cooling of the PDK gearbox and other areas (intercoolers and turbos possibly). These valves are controlled by these solenoids which I think are vacuum activated, but I'm not certain.

If this is the case and the ancillary components are cooled from the effective bottom of the engine, then if these valves were open from cold the engine would need to heat all of the coolant in these systems as well as the block before it reached temperature which would explain the long time taken to warm up. It would also explain why, on some occasions, the engine heats up quickly (as I would expect it to) and then the coolant temperature drops as these valves open on demand and allow cool "water" to enter the bottom of the engine. So, it could be that these valves have failed on your car (and lots of others it would seem) and that's why it always takes a while to warm up whilst on mine they were working OK and are now working intermittently only.

Alternatively, it could be that there's another explanation for what's happening, but I would have expected Porsche to be able to give it to me when I queried it, rather than initially saying there was a fault and then saying it was working "as they would expect"

Another odd thing is that the auto-stop feature, which isn't supposed to work till the car reaches "operating temperature", is working fine when the gauge is showing 70 degrees!

Curiouser and curiouser.....

 

[mullinsm]

The coolant doesn't flow through the rads until the thermostat opens, so the air flow through them makes no difference until the engine reaches temperature. If it did, the engine would never reach temperature at all.

As for worrying unduly, I'm not really worrying at all but I think that for the price we pay for these cars they should work properly and if mine is then Porsche should be able to explain to me why what is happening is happening. So far, they haven't been able to.

 

[mullinsm]

Update for those who may come after...

Spoke to another OPC who tested a 991.2 and it took 16 mins to reach operating temperature, so I'm going to conclude that this is, indeed, normal. However, sometimes the engine heats up far more quickly than that and the only logical explanation is that, on a cold start the car warms up the engine block and some ancillary parts as well (best guess is the PDK) and this takes approx. 16 mins or about 8 miles. However, if the ambient temperature is above a certain level, then the system brings the engine to temp first and then opens a valve to the PDK cooling system which causes cold coolant to flow in and cause a sudden drop and then a gradual recovery. If this is the case (and I'm only guessing) it would be interesting to know if manual cars are the same and why Porsche couldn't just tell me that when I first called them instead of telling me I had a fault......

 

[tscaptain]

To a greater or lesser extent this must depend on how you drive the car during the warm up period. If you leave it in auto and normal the revs will be pretty low. Drive it in manual and keep the revs in the 2-3k range it may warm up a lot quicker. Certainly better like that on my ancient 997.2 turbo....[]

 

[s2rjn]

I have read all this with interest after my experience this morning. Scraped the ice off my 991.1 C2S and drove to office with the heaters on max, after about 6 miles I could still see my breath in the car and realised there was no heat at all coming from the vents.....then after I played around with the temp (moving from hi to 27 and back to hi) a few times the heat suddenly starting and the air warmed up very swiftly!

Could there be a sticking valve/solenoid somewhere? ...I noted the car took longer than I'd have expected to get up to temperature too but after it did I had warm air. Is this a known fault? I've only had the car 2 months and this was my first (ice scrap) cold morning...

I have a Porsche Warranty so thought I'd gauge the opinion of the forum before considering taking it to the OPC

Anyone know of this problem on the 991?

Cheers

Rich

 

[richardfleming]

sounds identical to my problem with 991.1 C2 - they told me it was a known problem with 991 and replaced the part under warranty. see my post above - symptoms were identical to yours (barring it springing into life - mine stayed dead until a part was replaced)