Thermostat and Coolant Bleeding Issues

[monty23psk]

first is temp sensor, then is gauge, then is cluster. Besideds the sensor, I would try to get used parts to test. Also research if there is a way to test sensor. It should, you just need to know resistance range and how it relates to Celsius temps.

[iamcreepingdeath]

i figured i'd just buy a new sensor, its only $6.50.

And guess how things are today:

its like 48 degrees F outside, so i was driving my car, and it was running at 3/4 temp, then after a little hard driving it started going into the red.  I popped the hood and checked the lower passenger side coolant hose, stone cold.  Then guess what else.  After driving for a little while, the gauge settled on a tiny bit over 1/2 and stayed there ever since.  Also the whole time, the radiator and lower passenger hose were stone cold.  But the temp never went up to 3/4 again.

This is totally weird, i didn't even do anything to the car today.  What the poop is going on?

[monty23psk]

Do believe you sensor or gauge is off. If it is that cold outside, the temp of the engine but not be getting hot enough to open the thermostat and the top hose will stay close. But if you go by the guage it should. So my guess is guage or sensor.

Where are you located with that temp?

[iamcreepingdeath]

Do believe you sensor or gauge is off. If it is that cold outside, the temp of the engine but not be getting hot enough to open the thermostat and the top hose will stay close. But if you go by the guage it should. So my guess is guage or sensor.

Where are you located with that temp?

i am in Colorado an hour north of Denver.  Its freak weather actually, it was 80 like 3 days ago, its supposed to get up to 75 tomorrow.

[johnwoo]

mine does this too. the lower radiator hose stays cold when my temp gauge reads 1/2.  then after i flog it and warm it up the gauge will read a little past 1/2 -3/4 and eventually my hose will get warm.
so im thinking i have a faulty gauge or temps sensor reading hotter than it actually is.  also my gauge does the dancing trick so my nut on the back is prolly loose.  o well will do it all in one swoop.  
i'll follow this thread to see how the other sensor effects things.

[iamcreepingdeath]

ok dudes i put in the new temp sensor for the temp gauge, and what happened is now the temp gauge is much more steady and seems to stay consistently at a teeny bit above the halfway mark, which at this point is freaking good enough for me.  as long as it stays there and does no jumping around, i'll be happy.

as of now, what i have done to my M42 cooling system is this:

-"Mess under the intake" delete mod
-New T-stat (twice)
-New T-stat aluminum housing w/ new gasket
-Mechanical fan delete with an electric Volvo fan
-New water pump w/ metal impeller
-Coolant flush (twice) with 50/50 coolant/distilled water and Redline water wetter
-New DME temp sensor
-New temp gauge sensor/sender for the gauge cluster

and by gosh darnit my M42 better have a working cooling system by now.  If not, i am putting in an S50.

[johnwoo]

thats awesome news, looks like mine is up next for the "mess under the intake" cleanup and the sensors swap.  i've done t stat, radiator, waterpump.  still have to do the volvo fan and the clutch fan delete

[monty23psk]

Great news.

I noticed that if you give it a few more good bleedings, like 2 more,  you can even have the needle before the 12 o'clock positons. Imagine, I live in south Florida and dont have a fan clutch. I only have a Spal fan in place of the aux fan. So only the fan turns on with either the AC on or the temp radiator switch hits 91 degrees. Yes in rush hour traffic, my needles moves around but never get to 3/4 as my fan turns on high and that baby moves, 10 times more that the stock aux fan.

[iamcreepingdeath]

ok, so a question about bleeding:  do i bleed the coolant with the cap on or off?

[RED IS 91]

Cap on is the way I do it .I keep the rpms up to around 1500 then open bleed screw with heat on high with car at operating temp till clear fluid comes out (no air bubbles) .
Keep a close eye on the needle . Take car for a spin and repeat.
I've done it this way at least a dozen times with no issues.

[monty23psk]

per bpurcell website, which is the way I do it, and I believe the factory manual, you do it with the cap off. This way you can add more coolant mixture in the process after all the is spilling out the bleed screw. Last thing is to loose to much coolant and allow air back in.

[iamcreepingdeath]

hmm....  i will try it with the cap off then.

But as far as everything being fixed, well, not so much.

Today it was like 85-90 degrees, and the temp gauge went almost all the way up to the 3/4 mark, and this happened while driving on the freeway at 80mph.  I am seriously about to give up, i have replaced everything, i can't imagine why the temp would still be that high and unstable.

Also, the lower passenger coolant hose was just barely warm while the temp gauge was at 3/4.  All i can think of is that the T-stat is just not doing its job.

what could it be???  i am about to ditch this M42 for something else, i am so frustrated.

[RED IS 91]

If your thermostat is acting up or you have air in the system it won't matter how fast you drive.................

[iamcreepingdeath]

right, but its weird, this is the second new t-stat i put in, and i even drilled a hole in the top to allow air to bleed through if the T-stat is closed.

[dj91318is]

Here is my .02. If you leave the cap off how will it build up pressure? Try running it with out the t-stat it is used for quick warm ups in cold weather anyway you cant hurt anything it's a process of elimination at this point. You could have a defective Water Pump the blade may not be sticking out far enough to reach into the journal port correctly for good water flow. Hope you fined the solution be for you yank that 42. You could also have a restricted return water line some where. GL