How Long Can Thermostats Last? - PeachParts Mercedes-Benz Forum

shertex · #1 01-10-2011, 09:39 PM

My thermostat is seven years old (85,000 miless on it) and works perfectly. I know I've gotten my money's worth. How long can they last? Just curious what others have seen.

lietuviai · #2 01-10-2011, 09:42 PM

160K+ on my original one but YMMV.

retmil46 · #3 01-10-2011, 10:17 PM

On an MB diesel, who knows? I had an '87 Subaru wagon, bought brand new, kept for 18 years, and never had to mess with the thermostat.

On a Jeep Liberty diesel, I can give you a more definitive answer - 5 years - and it comes in it's own special housing and costs over $100.

pawoSD · #4 01-10-2011, 10:24 PM

I've replaced it on a few of ours....because they stuck open/ran cold. Its nice that the replacements are only about $15-20.

Cr from Texas · #5 01-10-2011, 11:45 PM

Mine's the original.
I hope this post does not jinx it to fail!

DieselPaul · #6 01-11-2011, 12:50 PM

I wouldn't replace it because you can, if its working, you've got a good one. I replaced one with a "superstat" from the stant, the bigger better one that is supposed to last longer. The one I removed was original and functioning but the motor was out of the car, so it seemed obvious, within 700 miles the superstat failed and overheated the car. It just locked shut. Put the original back in, no problems in 2 years.

This was on a GM 3800SC-II though.

You might buy a spare one for the 300D and put it in the trunk so you're prepared though.

shertex · #7 01-11-2011, 12:53 PM

Once the weather warms up, I'll be doing a complete coolant flush. So I'm trying to decide whether to replace then "just because," or leave it in till it fails.

DieselPaul · #8 01-11-2011, 12:56 PM

You're not going to hurt anything. But I think the actual answer to your original question is... there is no answer... lol. They don't really have any kind of typical life. Some stick open, some stick closed, some last for eternity. Kudo's to you for doing preventative maintenance though.

Diesel911 · #9 01-11-2011, 01:53 PM

I think that the original working one may be of better quailty than the newer ones.

If your Car has ever over heated; not due to the Thermostat; Thermostats some times go bad soon after the over heating incident.

In my life time I have had 3 new Thermostats that we no good right out of the box (not for Mercedes). One would not work at all; the other 2 would open at too high of a temp.

Test them before installing them to save youself the work of doing it again.
I say this because about 6 months ago I did not follow my own advice. I had miss placed the Thermostat during a Head Gasket change so I bought another and installed it without testing it.
I kept an eye on the Temp Gauge and it was on the way to overheating.

I removed it and tested it and sure enough it was opening at to high of a temp.
So if I had tested it to begin with I could have saved myself some time an labor.

cjbrown · #10 01-11-2011, 11:29 PM

I put a new water pump, belts, and 'stat in as preventive maintenance, 120K, just because it had never been done. All fluids, valve adjust, all filters, all fuses, all fuel lines, and it has a relatively new battery. Oh, and new tires, center bearing, front wheel seals, and motor mounts.

On a BMW 3-series, did all the same, all the hoses, and the expansion tank at 80K. I have never had new parts fail, just old ones.

josha37 · #11 01-12-2011, 02:00 AM

I have pulled thermostats that had corroded the center out and just turned into a plate with a hole in it... If your thermostat does not fail early on it will probably go until corrosion gets it. They are very simple little devices and very cheap, i change mine occassionally and recomend the same to my customers. Cheap insurance

, and it seems like dealer t-stats have much lower failure rates than parts stores but that can normally be assumed with most parts.

roundout · #12 01-13-2011, 07:31 PM

I found the thermostat broken in half in my Benz after I bought it. It was perfectly clean, as was the coolant. It looked brand new, other than that it was broken in half. I've never really trusted a thermostat and that only reinforced my distrust. At least on a 617 the fix is easy and cheap. On some cars it's expensive and difficult.

cjbrown · #13 01-13-2011, 07:40 PM

And relatively cheap.

The thermostat in our 3-series comes with the temp sensor and housing, $65 at a discount, about $100 retail. The dealer charges about $350 to replace one. I have replace it twice now in 95K miles. The first time it threw a code for the sensor, the second time it was sticking a bit and not warming up quickly like it did before so I knew it was starting to stick open.

MBDFahrer · #14 01-24-2011, 06:41 AM

I had just replaced my thermostat since it was stuck open. Its been replaced at least once before since the old one was rated to open at 75 degrees C. Too bad on my drive back to LA, my water pump failed

I guess I should've replaced that as preventative maintenance.

bobodaclown · #15 01-24-2011, 07:53 AM

They last till they break. Different factors involved, how often you change the coolant, type of water added (tap/distilled) and driving habits.