Change Your Thermostat!

[demarpaint]

Originally Posted By: OVERKILL
Originally Posted By: HTSS_TR
OE thermostat should failed open not close, when it fails the engine running cold which may pollute a little more than spec but will not damage the engine vs failed close.


This. Plus, if the heater was not blowing hot air, that's not a sign of a bad thermostat, that's a sign that there's no coolant in the heater core. It probably ate a head or intake gasket, dropping the coolant level and overheating.

 

[The_Eric]

Originally Posted By: OVERKILL
Originally Posted By: HTSS_TR
OE thermostat should failed open not close, when it fails the engine running cold which may pollute a little more than spec but will not damage the engine vs failed close.


This. Plus, if the heater was not blowing hot air, that's not a sign of a bad thermostat, that's a sign that there's no coolant in the heater core. It probably ate a head or intake gasket, dropping the coolant level and overheating.


It could also be that a head gasket failed, which put exhaust gasses into the cooling system, causing an airlock. Happens that way on the Northstar engines and the 3.1/3.4 engines, like the O/P's mom has.

 

[dlundblad]

This reminds me of a Jeep XJ 4.0 that came into work that was over heating. He asked me for my advice and I said if you have plenty of coolant and its still overheating, Id blame the water pump or the thermostat. I said I couldn't guarantee anything and he was out of ideas, but I used the expression "If this was my Jeep, ..." The thermostat was about $5 with a gasket while the pump was around $60. The gentleman knew going into it, it might not be the fix (for a Jeep owner, he seemed much less knowledgeable than even dumb me.) but he fixed it in the parking lot in about an hr.

Turned out to be a cracked block. He showed me where it was bubbling through a small pea sized crack. Turned out it had NO COOLANT too.

The 4.0 is tough, but not when its pushing 35" tires, stock gearing and being driven 25+ miles (after a day of wheeling) with no coolant.

 

[Chris142]

Originally Posted By: SteveSRT8
Originally Posted By: nwjones18
Also DO NOT BUY MOTORAD THERMOSTATS! Everyone I've ever had or installed has failed and failed closed... Get a Superstant or even better go OEM.


Funny there, as I have been running a Motorad in my car for many years now.

No one here can make blanket statements about "all stats" or "all cars" as the differences in performance and design of cooling systems as well as the engines they serve are too great...
we stopper using them.too many failures from that brand. I'm sure they make some good ones but many bad ones. The one i put in my jeep would open @178 one time and 203 the next etc.

 

[Chris142]

Originally Posted By: Lolvoguy
Originally Posted By: Chris142
Originally Posted By: WobblyElvis
Hot coolant circulates through the heater core regardless of thermostat position.
x2



UNLESS the interior temp valve has been set to "cold".

Had to explain this, never know who's reading
depends on the car. All 3 of ours just use a blend door to separate the hot heater from the cold evaporator. No heater valves in em ever.

 

[andyd]

Harrumph. In my automotive fix it career, I have only encountered one failed T'stat. It had 200k on it and developed a leak from a failed gasket at the throttle body. The original part. The pin wore and allowing the diaphragm to cock side wise and jam shut. I took it it out for the summer and had no drama commuting to Boston. Come fall, I drained the system, flushed and filled with fresh anti-freeze with a new one bought from my BIL's favorite foreign auto parts guy. These are the traditional bi-metallic spring type. There are newer types that use a heat sensitive pellet of something. I think T'stats get get a bum rap because they are the the next cheapest part after the pressure cap. My 528e has a very simple low coolant level sensor warning light. I have had 3 528es in 19 yr and had 2 others for spousal unit and kids. Not a single over heat in that time. The cast iron heads in my Jeeps could be get pretty hot and not melt. A blown hose or a belt breaking happened without further damage if you fixed or had lots of water. Water pumps need to be exercised. Seals harden, grease turns to soap. Impellers erode. radiators or heater cores plug up.

 

[Number_35]

I've never had a thermostat fail closed. Generally, they get lazy, and start to open a bit prematurely.

Aftermarket thermostats have been bad news for me. OEM only now.

 

[hattaresguy]

I have only had one t stat fail ever, typically they fail open.

 

[MCompact]

In the past 10 years I've replaced 4 thermostats:

1975 2002A at 36 years, 195k(still working, replaced as part of cooling system rebuild)
1995 318ti at 12 years, 11k(failed open)
2004 X3 2.5i at 9 years, 156k(still working, replaced as part of cooling system rebuild)
2007 Mazdaspeed 3 at 7 years, 131k(failed open)

 

[Dave Sherman]

Surprisingly, I've only had to replace one thermostat. It was either opening too early or stuck open, but it took a while to figure it out. It was only when I noticed the torque converter would lock and unlock at odd times, and the heater was getting warmer and cooler. That car didn't have a temperature gauge.

 

[MCompact]

Originally Posted By: MCompact
In the past 10 years I've replaced 4 thermostats:

1975 2002A at 36 years, 195k(still working, replaced as part of cooling system rebuild)
1995 318ti at 12 years, 11k(failed open)
2004 X3 2.5i at 9 years, 156k(still working, replaced as part of cooling system rebuild)
2007 Mazdaspeed 3 at 7 years, 131k(failed open)


Typo- the 318ti thermostat failed at 112k.

 

[Nick1994]

I know most of the time they fail open, my truck had that happen a couple years ago and my grandmother's Trailblazer had the thermostat replaced last week because it's been stuck open. My purpose of this post is to raise awareness a little bit, that sometimes preventative maintenance can save you and when you're in a sticky situation you may not have control of what happens.

 

[zzyzzx]

Originally Posted By: philipp10
Originally Posted By: oilpsi2high
This is what happens when you neglect to change the coolant on a regular basis.


oh complete baloney. If that's the case I should be having major cooling system failures as I have not changed coolant on a car in 15 years.


I agree. The only time I change coolant is when I am doing maintenance that requires me to drain the coolant. Once your car gets over a certain age or mileage you will be doing this often enough anyway. On a new car, I could see changing the coolant maybe once.

I would never replace a working thermostat.

 

[DBMaster]

I used to change the coolant every 30K on my Accord. When the car was eight years old I switched it to Dexcool. (Dexcool haters restrain yourselves). After that, I only ended up replacing coolant when I changed the timing belt (water pump gets done at the same time), radiator (plastic tank cracked near fill tube), and the small bypass hoses. Never had any troubles.

I used to change the thermostat every time I did the timing belt since I had to drain coolant to change the water pump anyway. I actually had one thermostat (Honda OEM) pop apart (it literally broke) and cause weird, intermittent overheating. Once I figured out what it was I just replaced it. I don't think I would do it as preventative maintenance in the future.

 

[dlundblad]

Why would you switch to Dexcool?

Not hating on it, but to me it sounds like you're putting ATF+4 in a Honda's transmission and not using what meets the cars requirements.

 

[DBMaster]

The Accord in question was a 1989 model. Dexcool was the latest and greatest thing. I had never heard of a 5 year/100K mile coolant. I had no issues at all flushing out the old stuff.

My ATF of choice in that car, btw, was Mobil 1 synthetic. The transmission started slipping badly at 300,000 miles and I had to replace it. The cooling system remained very clean up the point at which I wrecked the car - 353,000 miles.

 

[dlundblad]

Failed at 300k. Wow. I hope my Jeep lasts that long.

 

[rslifkin]

IMO, unless there's an issue with it, the stat isn't getting changed. I've only seen one fail (stuck closed during warmup one day) and it was 25 years old at the time. I've seen many others last a long time with no issues at all.

 

[DBMaster]

Originally Posted By: dlundblad
Failed at 300k. Wow. I hope my Jeep lasts that long.


All I ever did was 30K drain and fills (no filter to change). Initially I used Amsoil synthetic ATF since it was all that was available at the time. I switched to M1 when it appeared in stores (half the price). Today, I would use Honda DW1. I drove it hard. The non-planetary gear transmission had very noticeable shifts. I always thought that contributed to its longevity - very little slop during gear changes.