Antifreeze everywhere after temp sender install
 

I don't know what to do... I got a new temp sensor from fastlane this morning. I installed it and at first it didn't seem like the temp gauge was working but after about 10-15 mins it finally starting creeping up to 50c. I was at a red light and a guy next to me was screaming that my car was spewing antifreeze. I pulled over and opened the hood and there was antifreeze everywhere!

There are only 2 ways I see this. Either I left the expansion tank cap loose or the temp sensor is completely wrong and my car overheated.

Are the caps designed to loosen if the car over heats? The cap was loose when I first pulled over.

No expansion tank caps do not loosen. Where was the antifreeze coming from? What procedure did you follow when replacing the temp sender? Usually it just involves removing the old one and putting a new one in it's place without doing anything else to the cooling system.

Ok so maybe I left it loose. I hope... Would that be the reason why the reading was so low? It looks like all of the antifreeze came from the expansion tank.

Ya all I did was remove the old one and quickly installed the new one and replaced some of the antifreeze.

I'm going out now to quickly hit the head with a infrared gun and see what it says.

Says 71c but the gauge says 45... Is there a way to test the temp sender without using the infrared gun? I couldn't get an accurate reading yesterday with it.

My temps prior to installing the new temp sender would rise pretty quickly to 90c. I would say like 10mins. Now in 10 mins it barely hit 50c.

Can anyone tell me which temps are closer to realistic?

Might have an air bubble that needs to be burped. Air around the sender could be causing an inaccurate reading.

I am not sure what actually happened. If the temp was really 50C then it is unlikely antifreeze will be spilling everywhere unless the cap was not put on at all. It would not spill even it was loose at 50C.

Did you measure the resistance of the sensor before installation? Ohm it out at room temp and then at 50C and/or in boiling water. The resistance should increase but I do not have the spec. I use this HF Infra Red reader and the reading is rock solid. I calibrate it with a pan of boiling water and it is pretty spot on at 100C. Probably no damage done as your car has a cast iron head.

http://www.harborfreight.com/non-contact-laser-thermometer-96451.html

Ok well I just drove the car with the air on full heat and on 1st with high rpms for a minute. It burped and I refilled it. Ran it again and the expansion tank stayed full. The gauge still reads 40c when I start it and after 10mins of driving, it only hit 50c.

I have no idea why the antifreeze overflowed. Possibly I left the cap loose. Possibly overheated. Arg...

No I did not measure resistance of the sensor. Should I remove the new one from the car and test it?

I looked up the sensor part # for your car and it came up as 0055422617. It is a bit different from the one you have from Napa. I think they may be the same but I ain't sure.

You do not need to remove the sensor if you are only interested in 2 temperature. Measure the ohm when engine is cold and measure when it indicates at 50C and check against the spec. You really need to remove it if you are interested in ambient, 50C and 100C (with boiling water ). This will at least give you a ball part number when the car is running at 90C or there about.

Good luck.

I didn't get the one from Napa. I got the one from fastlane http://catalog.peachparts.com/ShopByVehicle.epc?q=&yearid=1984%40%401984&makeid=63%40%40MERCEDES+BENZ%40%40X&modelid=6233%3AED|100 00135%3AMBC|1518%40%40300TD&keyword=temperature&subcatid=P:240675@@Water%20Temp.%20Sensor&mode=PA

I will check the resistance when the car is cold then... ack!

The sensor from PP probably is the same, they have the proper MBZ part #. Sensor is a dime a dozen and costs peanut to make. The gut are ALL the same as it is made of a thermistor in a casing. I have a link with the resistance at different temp. The one you have may or may not follow the values but should track very close to it in 'shape' if you plot it against temp. If the car is REALLY at 50C then the engine should be OK to touch, but not at 90C. You really need a reliable IR probe to be confident otherwise it is a guessing game.

http://www.angelfire.com/my/fan/CTS.html

Good luck.

Thank so much! You've gone out of your way to help me. I appreciate it. I'm going to test it. I think it's definitely possible that the sensor is not working. After I test it, I'm going to put the old one back on and see what the gauge does.

FYI, I had a similar temp problem for which I tore my hair out. My temp gauge quit working. I replaced the sensor. The gauge would move a bit when warm but stayed at the 40° mark though the engine was plenty warm. I traced the wiring, checked resistance, cleaned fuses and replaced the electrical center. Finally started checking parts numbers on the sensors and discovered I had been given a different number. There IS a difference. Replaced it with the proper one and all is well. Just managed that this week after tearing my hair out for about 3 months.

Hey Bob. what car do you have? Where did you get it the sensor? I'm running some resistance tests at different temps now. I already see that the resistance is totally different. I put back my old sensor in the car, and now the gauge is reading like it use to (not sure if it's correct but I rather get a reading that's over then no reading at all).

Here are the numbers...

Old Temp Sensor

Boiling Water resistance @ 50
5mins later @ 250
10mins later @ 383
Freezer for 5mins @ 1300

New Temp Sensor

Boiling Water resistance @ 230
5mins later @ 1160
10mins later @ 1950
Freezer for 5mins @ 5000

What's interesting is that at each interval that I measured, the reading was about exactly 5 times greater in the new temp sensor than the old one.