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So now it's May 7 and 88 deg outside. The car got up to 228 and recovered to around 221-225 once I started driving. However once it reached 235 it slowly climbed to 245. As I was pulling into my garage it had reached 250. There was steam coming out from where the reservoir is, and could hear it bubbling in the bottle. Help! Are my fans not operating properly? Is there still air in my system? Could my water pump be faulty?
How many miles on the car? I had to have my radiator replaced at ~150K. In my experience, C4's and C5's are bad about clogging up the radiator over time with dirt, rocks, candy wrappers, grass... and reduce the cooling ability.
That's just been my experience with it. Good luck.
Sorry to read about your troubles. Not very much info to go in so I'll ask a few questions first.
1. when was the last time you thought the cooling system was working properly? What was normal back then. For example, my bone stock C5 normally runs below 200F in 90 degree ambient on highway driving so that is my normal.
2. what has been done to your car since it was at that normal state?
3. Do your fans turn on and suck air into the engine compartment? You can let your car idle until the engine temp rises sufficiently to turn them on. I dont remember the exact settings but they should be on by the time the temp reaches 235F. You can also check by turning on the a/c because they should come on pretty quickly at 88F ambient. Fans don't normally come on at road speed so non functioning fans would not explain high temps down the road.
4. Are you running a 50/50 mix of antifreeze?
5. Steam coming out of your reservoir- was it coming from the cap? If so, that makes me suspect you have a bad cap or it was not sealing to the reservoir.
A 50/50 mix at 15 psi boils somewhere around 258F.
Air does not normally get into the system unless there is a leak, it was incorrectly serviced, you have a leaky head gasket, or perhaps other reasons.
If steam is coming from your tank I would guess your surge tank cracked (very common problem with C5’s). Also makes sure you have the updated tank cap...should be 18psi.
C5’s are intended to run a little warmer than most cars. 215-220 is a healthy temp. Beware of anything below that. The car is not going through the proper heat cycles. Lots of people install 160 thermos and tune the fans for cooler temps without realizing they’re doing more harm than good.
I do have an 18 psi cap on reservoir. The passenger side fan comes on when I turn on ac. It is also on when temp rises above 220. I can't get a good line of sight for the driver's side fan, so can't tell it it is on. I will jack car up and try and get a look.
I am also running a 50/50 mix.
How do I check the fans in both directions (towards the fans and towards the control unit)?
Carlos, one thing to do is check the area in front of the radiator, the area between the radiator and the A/C condenser in particular. This area is known for gathering all sorts of road debris.
Here is an update. I discovered a crack in he upper left sea of the radiator, and also a leak from the hose attached to the water pump. Those two problems explain the runaway temperature once over 220, and air getting into the system. Thanks everyone for your input and suggestions.
Coolant Overflow Reservoir
