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SOS - Overheating after T-stat and water pump replacement
Long read but I did a lot of work and am at the end of my rope figuring out what is wrong here - I need some help!
Did a major maintenance service on the 04 CTT as it approaches 200k. Replaced all the various bits on the front of the motor with the car in service position. Pulleys, tensioner, rollers, alternator, ac compressor, water pump, thermostat, serpentine belt, upper+lower radiator hoses, diverter valves, etc
Vacuum bled the system and tried to burp it but it is running hot and holding at the 3rd bar. Tried the heater at max but it is only blowing cold air.
Figured the coolant is blocked somewhere so I went onto to do some troubleshooting:
- Checked and verified operation of the old and new thermostats in the water pipe housing with boiling water
- Checked all hoses for kinks, none found
- Checked coolant after run pump in drivers side wheel well. Pump is running dry, no coolant is flowing through those hoses.
- To check for blockage at those hoses, I removed the hard lines and ran water through them. No block.
- I then took the garden hose to the vehicle end of the hoses to check for flow, all good.
- Seemed like no coolant was flowing from the water pump so I pulled the upper hose while the car was running. I figured the upper hose should spray out coolant but nada came out. Those hoses have no blockage and the radiator pours fluid out so its filling/draining.
- Swapped out new water pump for old water pump again...still no dice
Car was working fine prior to bringing it in for maintenance. I'm stumped and am calling on the collective brain trust for help, please! What do you guys think it could be/have any troubleshooting tip? Can someone color in info on how the cayenne cooling system works? I understand the basics for a normal car but the CTT has a bunch of extra stuff in it.
Curious if both radiator hoses and any others that you can see crushed down during the vacuum fill?
Both upper and lower radiator hoses crush down during vacuum fill, didn’t think about checking the other hoses running behind the engine while vacuuming. The car does reach about -17 on the vac gauge and it holds vacuum.
Both upper and lower radiator hoses crush down during vacuum fill, didn’t think about checking the other hoses running behind the engine while vacuuming. The car does reach about -17 on the vac gauge and it holds vacuum.
If both hoses crush then you are getting vac to both sides of the thermostat. I assume the resivoir is still full after running and checking? I have a smaller compressor and am only able to pull about 20 in/hg. However, 1 vac is usually not enough. You can get about 2/3rds of the system full on the first vac and close to 100% on the second. I do a 3rd and wrap a towel around the exhaust filter because as the coolant comes up to the device during vac it will spray coolant everywhere. I like to make sure that I get as much filled as possible. I also do two vacs on the first and second before I switch the valve to suck coolant back in just to make sure I can get close to that 20in/hg as possible. When you open the valve to suck coolant back in don't crack it all the way open. I find it fills better if you let it refill a bit slower and you will notice on the gauge that it maintains higher vacuum during the refill portion of the process. Sounds like you did everything right and there isn't much to mess up during the process. You can even reuse the mls gasket that go's between the thermo housing top and the block. The water pump doesn't have any coolant passages in itself so that wouldn't be an issue.
Sounds like you still have air trapped somewhere. Park the car on a pretty steep incline angled so the coolant reservoir is at the highest point. Remove the beauty panels around the coolant tank so that from the drivers seat you can see the reservoir and if any air is coming up.
Start the car and once it warms up to where the thermostat is open, use the gas pedal to hold the RPMs around 2,000. Watch the tank to see if any bubbles are coming up from the hose into the tank. After a few minutes of this, do some revs which will agitate the coolant in the pipes and maybe free the trapped air. Keep an eye on the temperature gauge and shut down if it gets too hot. Let it cool all the way down (hours), then loosen the cap, top up the coolant level if it dropped at all, then repeat this process. It might take a few cycles of doing this before the temperature stabilizes at the correct setting and the coolant level stabilizes at the full mark. Once you've achieved this, drive the car again and see how it goes. Don't get too far from home so you can bring it back and park it if it starts to heat up.
No matter how I refill the cooling system after a water pump replacement on my GMC Sierra (AirLift tool, prefilling the radiator, etc) I have to go through this process probably 5-6 times before I'm done.
Try maybe more vacuum. I always go to -25 and then let it sit for a few minutes then fill. No problems at all. As others said, afterwards rev the engine to 2500 to 3000 and make sure the heater gets scalding hot. Then check level when it cools down to see if the coolant dropped. My $0.02
J’sworld - thanks for the tips and diagram. I usually do 3 cycles of vac/fill as well. The reservoir is always full by the last cycle.
Petza - thanks for the detailed reply. Would air trapped in the system explain why I can’t get any coolant to be pushed by the water pump? And 5-6x, wow!? I let the cayenne run and boil over twice before going back in to troubleshoot further each time. I have vac filled it before without trouble so this is all new to me, only exception is that the prior fills were just the radiator and hoses versus loosing coolant from the big areas this time.
Partsguygt - the best vac I can pull on the system is down to -17/18. The eBay vac fill kit I have doesn’t seem to be able to create a stronger vac than that even though my air compressor runs up to 145psi.
Partsguygt - the best vac I can pull on the system is down to -17/18. The eBay vac fill kit I have doesn’t seem to be able to create a stronger vac than that even though my air compressor runs up to 145p
It does sound like you have air in the system. Make sure you have interior heat on full blast when burping.
I had to make several "enhancements" to my $50 or whatever it was eBay vac fill kit before I got it to work to my satisfaction. Lube up the main screw (I think I used anti-seize this time), this allows much better tightening of the spreader screw, as it was leaking vacuum around the seal before this. I also replaced the quick connect, as the one that the kit came with did not fit either of my couplers. This allowed me to draw down to -26 in with my 29gal HFT compressor.
Even with that, -26 was barely enough to fill a 1.8L Toyota 2ZZ engine in one go, which takes just over a gallon of coolant. I have not done a coolant fill on the Cayenne GTS, yet, but I imagine multiple vacuums and/or heat/cool cycles would be needed to fill the several gallons that the Cayenne takes.
Petza - thanks for the detailed reply. Would air trapped in the system explain why I can’t get any coolant to be pushed by the water pump?
Yes, the vanes on the water pump can cavitate and it won't be able to prime if there is too much air inside the housing.
If you can't pull more vacuum, I would try letting it cool totally down and then drive up/down a steep hill if you have one close or drive the front and then rear up on ramps as a quick and easy effort. Did you make sure the water pump was not faulty before installing by spinning the pulley hub and watching the impeller turn? Crazier things have happened than faulty new part slipping past QC.
Perhaps find someone nearby who has an AirLift Bleeder. Thats what I have used on my CTT with 4zone and on several other Porsches/VWs/Audis that I work on. Look at the Airlift gauge. Seems like 17 isn't enough. https://www.uview.com/site/ywd_uview..._inst-book.pdf
Last edited by PartsGuyGT; 07-26-2018 at 02:30 PM.
Reason: Adding information
17 is enough. You just wouldn't be able to get a complete fill off the first vacuum. On the flip side, to much can cause harm. Most all the sealing pints in the system are designed to hold pressure, not vacuum.
17 is enough. You just wouldn't be able to get a complete fill off the first vacuum. On the flip side, to much can cause harm. Most all the sealing pints in the system are designed to hold pressure, not vacuum.
I searched high and wide for any cases of vacuum bleeding damaging anything before I purchased one, and came up empty (except for cases where components were on a brink of failure anyway, and I would say there's no better time to find that out then before filling and driving off). Especially on systems where vacuum filling was the intended method, which I believe modern Porsche's all are. More vacuum = better.
The only time you need to exercise caution with vacuum bleeders is on low-pressure cooling systems, which have smaller tubes and such due to only requiring 2-5 psi vs 15+ psi for a normal system. I think Prius is one such example.
I searched high and wide for any cases of vacuum bleeding damaging anything before I purchased one, and came up empty (except for cases where components were on a brink of failure anyway, and I would say there's no better time to find that out then before filling and driving off). Especially on systems where vacuum filling was the intended method, which I believe modern Porsche's all are. More vacuum = better.
The only time you need to exercise caution with vacuum bleeders is on low-pressure cooling systems, which have smaller tubes and such due to only requiring 2-5 psi vs 15+ psi for a normal system. I think Prius is one such example.
Good luck finding components that AREN'T on the brink of failure in a 10+ year old Cayenne, especially turbo lol. Doesn't hurt to err on the side of caution. This is what I can tell you. My Cayenne now has additional cooling plumbing, including larger/modified lines, water cooled external wastegates, and additional capacity. When air vacced fresh with a truly bone dry system including every single line and heat exchanger, 17 was not a problem.
Not trying to be a wise-*** here, but... you won't get water out of the hose to the radiator if the thermostat is not open and the engine has to be warmed up for the thermostat to open. I'm going to assume that you are sure the engine is warm enough for the thermostat to be open so water SHOULD be coming out the radiator hose, so I'll put the *** hat back on now. But if the heater is not getting hot, that's a pretty definitive that water is not moving through the cooling system normally. I think the suggestion for using vacuum fill 2 more times (maybe 3 more times if you still were adding coolant after 2 more tries with the vacuum filling) would be the best next approach. I had this problem with a BMW and had to vacuum fill several times to get out all the air. And somehow, the bottom radiator hose was dislodged somehow so that it was still in place on the radiator, but the spring clip latch was no longer latched into the fitting on the radiator, so the bottom hose had backed off its seal slightly allowing coolant to escape, which seemed to happen a lot after the car was parked and cooling-off. I eventually noticed the spring latch wasn't in the locked position and got the hose reseated properly and latched into position... that was the final piece of the "why is this still overheating?" puzzle.
07-26-2018, 12:23 AM
SOS - Overheating after T-stat and water pump replacement
