99ZombieSport

Not to beat a dead horse but I ordered one from e-bay (part number: 52028186ac) and it was the motoRad. And why do northeast dealerships want $40 and up for that same thermostat.

cruiser54

As for the $40, I don't know. It's $24 or so here.

As for the MotoRad stats, I don't think the ones we have available to us in the aftermarket are built to the same spec/design as the OEM.

1991Jeep_Man

Another Update: my rockauto MotoRad unit is performing better now that air is working its wait out. Still have some slight fluctuations when cruising (but it never dips below the halfway mark... only down to just above it so 175°?) with just slightly worse (to the halfway mark) after the first and second warm up "cycles". While idling or slow cruise, gauge stays right in the sweet spot about 1/8" from 210.

Question: out of curiosity, is the back of the cylinder head where the gauge sensor is the hottest spot cooling system wise? I would think it is at the thermostat housing... so perhaps what I am seeing is the rush of cooler coolant hitting the back of the head BEFORE it gets to the tstat, causing it to shut. I have considered relocating my sending unit to the thermostat housing where the ECM sensor sits...

djb383

I would think the front of the head, where coolant exits, would be slightly hotter than at the back of the head. Coolant enters the front of the block and exits at the rear up into the rear of the head and out the front of the head. Not quite sure about the range your needle floats? Can u explain your low to high on this pic?

1991Jeep_Man

During first start fluctuations, it gets down very close to what is marked 155°. During cruising flux, it will only drop to just a bit before the 182.5° mark. During idle or slower cruising or more stable temps between the engine and rad, she sits right at the 182.5° mark. Heat is blowing nice and warm. Cold start warms up faster. When the temp does flux down, it is very quick to warm back up... hence why I think it is just the rush of cold coolant hitting the temp sender before the tstat. That and the extreme cold I am sure.

djb383

Does the needle rise to at least half way between 210 and 182.5?.....that would be about 195. I would think with a properly functioning 195 stat, the needle might drop ever so slightly (5 degrees maybe) from 195 but not 40 degrees to 155. If the heater is still good when the gauge shows 155, I'd say your gauge is malfunctioning.

sturoc

That first overheat I believe the result of two things:
Extremely cold overnight temps: we were below 0 for 3-4 days.
XJ sat for 2 days in it.
Also not a great coolant mix and what turned about to be a small radiator hole. there may have even been some ice in the system.

The other day was the t-stat failing: CLOSED.
It was a dealer part ( 24 bucks no less!) MotoRad with a bleed hole jiggle valve in it. So there was a small amount of steam blow thru The upper hose was a couple years old and had developed a nice hole near the clamp.
Now:

Being stuck at home due to this issue, a friend picked up a 195deg Stant SuperStat not the cheap one But also not the fail safe.
He went to the wrong parts place, kinda had no choice at that point since I don't live in town.
Oh Well I figured process of elimination as to what brands are good / bad.

SuperStat is nearly identical to the dealer MotoRad t-stat I took out.
but w/o bleed hole. So drilled a bleed hole (slightly smaller than an 1/8" )
Put it in, got all the air bubbles and bout 3-5 mins warmed up to normal op temp. Heat good, no leaks.
Ran the XJ all day round town and took a 30 min long highway run .
Outside temps round 55-60.
Stock temp gauge was very steady, more than with MotoRad t-stat. Running at 190-200 deg all day.

btw: NO discoloration in oil or coolant, exhaust is normal. no smell of coolant or steam. the 216K 4.0 runs smooth as always.
So I am not inclined to think it is another cause.

Parts can fail and with the thousands and thousands of t-stats being made sometimes I ain't surprised!

djb383

Don't suppose u tested the dealer stat?

sturoc

Heating a pot of water to boil (which is 212 degrees btw) and watching the dealer MotoRad part do absolutely nothing. I'd say it was a bum t-stat.
Even without doing that, it is safe to say that when you don't have heat and the temp gauge rises up in a couple of minutes. = Bad t-stat .i.e If everything is good such as clean coolant and good radiator and water pump.

Of note : an old mechanic gave me a tip to lessen air in the system After doing a water pump / t stat or other cooling system part replace. Refill thru the heater intake hose. It will go right into the block and fill to the head. Then top off radiator as needed.I tried it and only had a few bubbles to bleed out via the open cap.

djb383

About how long was the stat in the boiling water and how did u get it to 232? Bummer, hope u got your $24 back.

prcherokee

The higher in elevation you are ,the lower the the temperature to boil water.

The boiling point of water is typically considered to be 100 °C or 212 °F. Pressure and a change in composition of the liquid may alter the boiling point of the liquid. For this reason, high elevation cooking generally takes longer since boiling point is a function of atmospheric pressure. In Denver, Colorado, USA, which is at an elevation of about one mile, water boils at approximately 95 °C or 203 °F.[7].

sturoc

Regardless of the actual boiling temp achieved, it boiled and never opened.
A ways back did the boil test with another t-stat kept as a back up,. It opened 'n closed as it should. Both tests were with the t stat in the pot as the water heated up, similar to a cold engine start and warm up.

.... and yes I did get my $ back from dealer !

djb383

I guess it is possible that if elevation was high enough (pressure low enough) that a properly functioning 195 stat would not open, or be very slow to open even slightly, in boiling water on top of a stove.

Firehawk068

In an open pan, that would be somewhere around 9,000 feet altitude......
That's why keeping a clean, and properly functioning radiator pressure cap installed is so important for us who wheel at high altitudes....(I routinely run trails in the 10,000-14,000 ft range)

SuperRA

I just bought a thermostat off of ebay. Part number 83501426 (with the 3 gaskets) and it seems like it's a really old (possibly 20 yrs old as there seems to be a date on the box of 9/93) NOS piece before they changed to Motorad. What do you guys think, as long as it works in boiling water, it should work fine?