singlecoiled

Long time lurker but first time poster.. I'm looking for some direction and maybe confirmation of a problem I'm having with my 2000 Boxster 2.7.

Problems: engine overheating that coincides with hot air not working

History: overheating problem this summer that was fixed by replacing ancillary water pump from resovior and changed thermometer. There are no leaks of coolant.

Where I'm at: yesterday I pressurized the cooling system with a Uview Airlift and was able to hold 25 which tells me there is not a leak. I'm in the process of draining the coolant today.

Doesn't appear that there is any oil in the coolant or coolant in the oil (changed a few weeks ago).

My thoughts are that the thermometer isn't opening up allowing coolant to do its job. Any pointers, tips, suggestions, etc?

Macster

Overheating coupled with lack of hot air suggests the coolant isn't flowing which could be due to a T-stat failure. You write you replaced the "thermometer". I assume you meant thermostat (T-stat). Did you test its operation in a pot of hot water on the stove to ensure the T-stat opened at the right temperature and opened fully?

While a bad one out of the box is rare this is why new parts come with a warranty.

If you are sure the serpentine belt is routed correctly then you are probably looking at removing the T-Stat and checking first that it is installed correctly and then it is the right part and last but not least testing it in a pot of water on the stove with a thermometer to confirm it is opening at the right temperature and opening fully. Its opening temperature should be stamped on the unit somewhere and is probably in degrees Centigrade.

You can "test" the T-stat while installed but I'm reluctant to detail this due to the risk of getting near a working engine and its accessory drive. You can start the cold engine and let it idle and while it is idling from under the car -- and being *very* careful -- check the hoses from the water pump feeling for any signs of warmth which comes from the T-stat opening and letting some hot coolant through.

Instead of using your hand to feel for this, better yet would to use an infra-red thermometer that you could just aim at various places on the engine around the water pump and the hose connections to monitor the temperatures at these various places.

If you observe the block/water pump housing and other areas nearby getting warmer and warmer and yet the hoses and such from the water pump to the radiators (and the return hoses) staying dead cold this pretty much confirms cooling is not flowing. You'll have to remove the T-stat and test it and while you are "there" I suppose check the water pump to make sure the impeller is not spinning freely on the shaft, that all the vanes are present, and even that the vanes are oriented in the right direction.

singlecoiled

Thansk for chiming in Macster.. You've been a great resource to many other's issues!

Yes, I meant T-stat. I've drained the coolant and pressure tested it again and I can hold 23 for more than the 20 seconds it reccomends to confirm as "not a leak". my air compressor doesn't let me get much higher than that unfortunately.

2 things I noticed..

I only seemed to drop about 2, maybe 2.5, gallons of coolant out as I followed the step by step tutorial on Pelican Parts. Where is the other 2+ gallons?

I removed the thermostat at is is stamped 99, meaning that the low temp T-stat I paid for was not swapped out and this is the original T-stat.

I've searched for a tutorial on checking the thermostat but cannot seem to find on specific to the Boxster. do you have a link on testing the T-stat?

Macster

Maybe the other 2+ gallons of coolant is missing? It is not easy to refill this cooling system without using a vacuum lift system. The procedure involves putting in as much as one can and then running the engine and even once warm raising RPMs to IIRC 5K momentarily then adding more coolant and repeating this until the system is full.

Might add it is possible whoever did the water pump job might not be that familiar with the car and might not know the system takes as much coolant as it does.

Regardless, if the system is low on coolant there may not be enough for the water pump to circulate properly and the engine could run hot.

'course, at some point I think the low coolant warning light would come on and one would find the coolant level in the tank way down.

You have to be careful. The tank can develop a stain that based on my experience can mimic coolant that one can look at the tank and believe the level is fine, mistaking the stain for actual coolant. The old trick of moving the car to observe the coolant level line moving doesn't work well as the car is so stiff that I at least end up moving around so much in trying to make the car move I can't really see the level. What I have done only to find the level was actually down quite a bit was to remove the cap -- with the engine/cooling system cold -- and the screen and shove something down in the tank and see where the level was.

There is no tutorial on testing a T-stat. The way it was described to me and the way I did it was to take the old T-stat and the new one and drop both in a pan of water on the stove and heat the water and monitor the water temperature -- I used a digital cooking thermometer that I used for auto related stuff not for cooking -- and observe at what temperature both T-stats opened and observe how open both were.

The idea is to ensure the new one opens at its stamped temperature and opens fully, at least like the old one, although this assumes the old was the right T-stat and was working fine. The few times I have replaced a water pump and T-stat both were factory original items and while the water pumps were bad the T-stats were apparently working just fine.

singlecoiled

Bingo!

The car was gallons light on coolant and most likely had the difference made up with air in the heating unit/front radiators that prevented the heater from working and also provided false reads on coolant level. I had a gallon total in the resevoir with another quart+ spilled as I disconnected all the hoses today.

I drained unit, properly pressurized the system with the Uview Air Lift and filled with just short of 4 gallons of coolant. Heat magically started working when the engine was fired up and the thermostat didn't cross 180 after some hard driving.

Considering there was conversations about "bad headers" from a second opinion mechanic, I'd say the $100 I spent on the Uview paid for itself.

In retrospect, the overheating problem I had this summer was from the radiator replacement 2 summers ago and improper filling of coolant/lack of coolant in general. Wish I had the $600 and 5 weeks I went without the car this summer.

I appreciate you chiming in and providing some guidance.

Macster

Glad I was of some assistance and glad to read you got it sorted. Now you need to make up for lost time and enjoy the car.

deepee

even if you refill with a vacuum system, always bleed the system ! air pockets can cause engine damage !
http://www.pelicanparts.com/techarti...ATER-Flush.htm
http://www.renntech.org/forums/topic...r-in-radiator/

Schnell Gelb

and if it just will not bleed,read this:
http://986forum.com/forums/performan...blems-fix.html