M20 not up to temp?

[Toodaloo]

Hey what's up guys, quite new here as I just picked up my 89' 325i a few weeks ago.
Well I've been noticing something funky. When I bought the car the Previous owner said the temp gauge stays around 1/4 and never reached half but goes up in traffic. Lately I've been noticing that if there's low load on the car and it's cold outside the needle will dip bellow 1/4 and be in between 1/4 and the blue mark. That's way too cool right? In the past few days it's been doing it quite a bit and I actually haven't seen it go above 1/4 since last Friday. I had the car inspected pre purchase by north bay Bavarian and they didn't mention anything about the thermostat missing or what not.

So what do I have to replace: Thermostat?
If so then can anyone direct me to a good resource I can buy one from?
And if not the thermostat give me some thought as to what it can be?
Thanks,
Andrei

[dnguyen1963]

You have the wrong t-stat. Contact Blunttech and tell them the year of your car and they will get you the correct one. Your fan clutch needs to be replaced too.

[Jaxx_]

thermostat is probably stuck open(failed part) or the thermostat is the wrong temperature. Some people will use a lower temperature thermostat to prevent overheating issues, but it is only a band-aid and really just buys you a minute or two, instead of fixing the real issue--lack of cooling.

the 1/4 mark is about 160F, which is a bit cool, but not horrible. My car has a similar thermostat and runs fine. You might get better fuel economy with a proper temperature thermostat, and possibly longer oil life. It also depends on how you drive the car.

However, a missing thermostat is pretty bad because it can cause the oil to not reach operating temperature causing premature wear on motor internals, and additionally causing excess fuel to be injected (cold start loop) and even worse, wash cyl walls with fuel, causing lack of lubrication and eventually causing the motor to lose compression. I won't get into the lack of expansion of the metal parts within the motor.


Long story short, replace the thermostat with one that allows the coolant to reach operating temperature and don't drive the car hard until you do.

[Jaxx_]

Your fan clutch needs to be replaced too.

not definitive.

[Toodaloo]

Alright. Is blunttech a forum member or a vendor? Coming from a wrx, I'm not sure how the clutch fan works. I know that when I look at the engine running the cooling fan infront of the rad (connected to the engine) is running but I'm not fully aware of how it works. I'm assuming it should always be running? Or only when it reaches a certain temp?

[Jaxx_]

Alright. Is blunttech a forum member or a vendor? Coming from a wrx, I'm not sure how the clutch fan works. I know that when I look at the engine running the cooling fan infront of the rad (connected to the engine) is running but I'm not fully aware of how it works. I'm assuming it should always be running? Or only when it reaches a certain temp?

it is always running, but it won't always have 'tension' on it. it is a viscous fan clutch. Try searching for the "newspaper test"

[Toodaloo]

One more question I'm sure swapping the thermostat is a straight foreword job, but do I actually have to drain the coolant to do it? Or am I able to just pop off the hose and housing without spilling any coolant?

[cgk_iii]

Drain the coolant from the radiator. Otherwise you will make a mess if you just start removing hoses/the thermostat.

[Dirty325ix]

Yea the thermostat housing is halfway up the block you will definitely want to drain the coolant

Since you just bought the car maybe a good time to just replace the timing belt while your there

[rturbo 930]

Alright. Is blunttech a forum member or a vendor?

http://www.blunttech.com/

http://www.r3vlimited.com/board/member.php?u=8939

[mitchlikesbikes]

before you do anything you should verify your temperature with an infrared thermometer. temp gauges are not always accurate.

[Toodaloo]

P/O did the timing belt last year ~20k miles ago. I'll just do the thermostat for now. Anything else I have to change at the same time? And where should I go for coolant? I'm assuming a 50/50 coolant distiller water mix correct? Should I go to the dealership or any other vendor?

[15Michaeljoseph]

P/O did the timing belt last year ~20k miles ago. I'll just do the thermostat for now. Anything else I have to change at the same time? And where should I go for coolant? I'm assuming a 50/50 coolant distiller water mix correct? Should I go to the dealership or any other vendor?

Depends how professional you want to be. Some people claim the wrath of hell will be upon you and your family if you don't use oem
coolant, but NOTHING bad is going
to happen if you just use regular old green 50/50 which is quite a bit cheaper. I like to buy the limited edition duck dynasty bottles personally.


--Mike

[Toodaloo]

Well changed the thermostat. Turns out the previous owner replaced it recently with a 75 degree model date stamped 03/13 (it wasn't stick open). Replaced with an 80 degree and filled in and bled with new coolant. The gauge does the same thing. I know it's up to temp because it's way too hot to touch, the gauge is super wonky and fluctuates between half way between cold and 1/4 to 3/8. Mostly stays around quarter but not always completely stable. I'm assuming it's just the temp gauge from age or what not. I'm thinking of purchasing a vdo water temp gauge and just relying off of that rather than 26 year old electronics. Heater blows hot and it seems to run fine. Any other outside ideas?

[4x4_e30]

Tap the speedo cluster right where the temp gauge is with your finger tips as hard as you can. Works for me half the time.