engine hot, loss of coolant - 986 Forum - The Community for Porsche Boxster & Cayman Owners

glenn davis · 05-05-2010, 06:32 PM

My 2002 S has been loosing coolant. the engine got hot but the temp gauge showed normal. When I removed the cap the coolant level rose higher in the tank. The engine was running bad. after it cooled, it runs fine. The car has 65,000 miles. I have the new tank cap and have replaced the o-rings under the cap.
How can I tell if it is the water pump?
Thanks,
Glenn

Lil bastard · 05-05-2010, 07:01 PM

A waterpump failure is usually (but not always) progressive. It begins by having some weeping from the pump cover where the shaft extends to the pulley.

Another issue with the Boxster waterpump is disintegration of the plastic impeller inside the pump. This too is usually progressive and as the impeller degrades, so does the car's ability to run in a normal temp range.

From what you describe, it could also be several other things you'll need to rule out.

It could be a failed or failing 'T'stat.

It could also be the result of air in the system - if you lose coolant, especially a lot of coolant, you need to fill and bleed the system of any air. There is a procedure for doing this and also a cooling system bleed valve which lives under the cover plate through which the coolant tank neck and oil filler neck protrude. You pry this up and then lift the D-ring on the coolant bleed valve. Run, drive the car a few miles with the valve open, being careful to keep the coolant level up (bring along a jug of pre-mix). Then close the valve and top up keeping an eye on the temp for the next few days. If it spikes again, not all the air was purged on the first attempt, re-bleed the system again.

I'm sure your issue is one of more of these things. Good Luck!

Cheers!

ARModen · 05-06-2010, 09:52 AM

Quote:

Originally Posted by glenn davis

When I removed the cap the coolant level rose higher in the tank.

DON'T do this! Here's the deal. Your coolant is under pressure. The pressure keeps the coolant from boiling even though places in your engine will be over 212F (100C). When you pop the cap on the coolant system you flash boil all the coolant in the hottest parts of the engine. This expanding steam will push coolant out of the engine into the reservoir. That can cause overheating and scaling in your engine. So avoid the urge to pop the coolant cap open until the car has cooled off significantly.

If the temperature indication in the car is in the normal range of operation 180-220 (depends on thermostat) then the impeller is functioning sufficiently. A failing pump bear may leak, or you may have a nicked hose, or a leaking reservoir. There are a lot of things that can cause you to lose coolant. Can you post what you mean by "running bad?" Take a good look around the underside of the car to see if you can locate where the coolant is going.

Steve Tinker · 05-06-2010, 02:48 PM

While you are checking for your coolant leak, also inspect your oil quantity and make sure it doesn'y have a creamy consistancy, ie coolant mixed in with the oil.....

glenn davis · 05-06-2010, 04:40 PM

Today I removed the plate behind the seats to check the pump for noise. It sounds ok. The pump is not leaking. There are no leaks anywhere, I lost some coolant near the right rear tire last week. I replaced the o-rings under the coolant cap. Today I also drove the car with the release valve open. At an idle I could see small bubbles while looking into the tank. On the way back home the car started
running rough. No engine light came on, but the other day while returning home from out of town, the check engine light came on, it was running like it had bad spark plugs. When I pulled into the drive it seamed to be overheating, smelled not good. After it cools, it runs great. Could it be the T-stat? Also, I am getting plenty of heat out of the heater it that helps. I am a DYI, but I sure would like to know where to start.
Thanks for all of the comments so far.
Glenn

brett914 · 05-16-2010, 06:59 PM

I just completed a pump replacement on my 02 Boxster S. It had to be about the easiest water pump replacement I've ever done (so far). The wierd thing is the car still overheats event though the reservior appears full. (I will take the bleeding suggestion above)
On a related note, the plastic impeller on the old pump had all its fins chewed off (new one is metal)....are those little pieces of plastic in the system causing issues?

jhandy · 05-17-2010, 07:28 AM

The fins then are still in the system, restricting flow, somewhere, hopefully they are stuck where the hoses bend or attach to the radiators.

If it is in the motor, then its bad.

Surley the enginers at porsche thought of this and made the flow from the pump to the front, to the radiators, then to the motor. So if anything broke loose, it would be stuck in the first radiator.

James

brett914 · 05-17-2010, 01:32 PM

JHandy,

That is exactly the news I had hoped to hear!
I will feel less hopeless pulling hoses off if I feel there is a good chance those little pieces aren't in the water jackets!

Brett

seningen · 05-17-2010, 02:46 PM

Quote:

Originally Posted by glenn davis

Today I removed the plate behind the seats to check the pump for noise. It sounds ok. The pump is not leaking. There are no leaks anywhere, I lost some coolant near the right rear tire last week. I replaced the o-rings under the coolant cap. Today I also drove the car with the release valve open. At an idle I could see small bubbles while looking into the tank. On the way back home the car started
running rough. No engine light came on, but the other day while returning home from out of town, the check engine light came on, it was running like it had bad spark plugs. When I pulled into the drive it seamed to be overheating, smelled not good. After it cools, it runs great. Could it be the T-stat? Also, I am getting plenty of heat out of the heater it that helps. I am a DYI, but I sure would like to know where to start.
Thanks for all of the comments so far.
Glenn

Is the CEL still on?
Can you pull codes from the OBD-II

your CEL may or may not be related to your coolant issue.

do you still get water near your right rear. was it overheating when this occured?
was it after sitting you noticed -- or while running?

There is an overflow tube there as well as the possibility of a cracked
coolant resovouir that maybe only leaks under pressure?

Is there any oil in your coolant or vis versa?

mike

jhandy · 05-17-2010, 07:31 PM

those plastic fins have to be in the system somewhere.
I have found on the net that the water goes from the pump, to the motor, to the front drivers radiator, to the center, to the passanger, to the thermostat and rtn to pump.

I do not think that the pieces and small enough to get into the radiator fins, so I would take off the hose from the drivers intake. Then look in the radiator, unhook the outtake of the motor, and run pressure through it. If there are no pieces in this system, then they are in your motor.

I dont know how you would get it out. maybe run water under pressure in reverse from the outtake to the pump, blowing anything that lodged in there?

anyone have Ideas?