Solved: 98 Ranger 2.5 Water Temp Gauge and Heat finally fixed

[beech2000]

Success.
Long winded read but if your desperate as I was you will find this interesting.
As I said on a mission and feel good about finally solving my low cab heater temp and pegged to zero water temp gauge mystery that has plagued this 98 2.5 4 banger for many years. The truck is a very used up ride that my son uses as his daily driver. The water temp gauge has never really worked and cab heat was fair at best.

Here lists a summary and observations of the event.
1) Upper radiator hose was always warm but never hot
2) I Changed out the thermostat paying particular attention to the seating legs. The old one came apart in 5 pieces. Fixed???? nope read on.
3) The T-Stat housing was deformed and leaking. I took the housing to my belt sander and trued the mating surfaces flat. Installed a new seal and bolted all together. Leak fixed and upper radiator hose now cycles hot then warm as it should.
4) Still had only fair temp amount of cab heat and gauge still pegged below zero.
5) Next I replaced the water pump due to possible eroded impeller. This was not my case. Pump impeller was normal and unit not leaking. Oh well.. Onward
6) The gauge temp sender was next on my list. with an ohm meter I found the 2.3/2.5 uses two. Grey colored One for the ECM and the other one is black for the gauge. THEY ARE NOT THE SAME!!!
7) Since the sensors are mounted in the plastic T-Stat housing, Two wire sensors are required. Most US corner auto part stores only stocked the ECM grey colored piece for the 98 2.5. No matter what I tried couldn’t find the correct sender.
8) I knew by shorting the two leads for the gauge together my temp pegged hot so I knew the cluster was normal and I needed a sender that dropped the resistance below 10 ohms when hot.
9) I found the correct 2 wire sender at NAPA. It took me bringing my fluke DVM meter with me. Jeff at NAPA Kennesaw, GA was diligent in finding the right one. The forth piece he brought me was the correct one. It measured 2500 ohms at room temp and using a lighter watched my DVM drop rapidly to 4 ohms. So after $40 of nonreturnable sensors from corner AZ’s I now have the correct 2.5 Fuel temp sender unit. I confirmed it now working in vehicle while holding sender with electrical connector plugged and using a heat gun the gauge inside was now responding. Yeay!!!
10) Reassembled and topped off the coolant with fingers crossed. Ran the engine and brought her up to temp.
11) WTF. No heat and no temp gauge. I can’t believe this…..
12) Burping the air helped the cab heat but gauge still wouldn't move from cold. (Insurance company almost has a claim on this as I almost lit her on fire). Kidding
13) So now what???? After reading over and over carefully looking at the system I noticed one thing. All four hoses at the heater control valve warm at best but never hot. Hmm
14) I noticed the arrow on the heater control valve was plumbed to the wrong ports. Easy fix. Simply swapping the return and pressure ports on heater control valve should fix right? Nope all four hoses warm to the touch after 20 minutes of engine running at idle. Man.... Kicking my butt
15) Hmm... I noticed when manually pushing in on vacuum valve gauge moved slightly... Then when I release the gauge would go back to its happy buried below cold. I'm on to something....
16) Also during all of this every time I moved the valve lever swishing noise in the heater control valve was heard. Strange as had bled air out of those lines over and over.
17) I left all clamps of hoses while actuating lever and letting coolant leak ever where when all of a sudden all for hoses were blazing hot!!!!!!
18) clamped everything and guess what???? Yeap... Gauge reading in the middle and cab heat like I haven't felt ever.... Wow....!!!
19) So air pocket in the T-Stat housing and everywhere else for that matter is my only explanation.
20) Strange too cause I had purposely left the sender finger loose at one point for bleeding purposes but must not have given it enough time.
So I fixed a leak at T-stat housing, replaced a bad thermostat. Replaced a water pump for no reason, plumbed the heater control valve correctly. Replaced the water temp sender with the correct part from NAPA. Also I noticed that while monitoring the ECM live with my Blue Driver module the engine temp went from 135F to 190F. I should be seeing better gas mileage as well.
Oh. I almost forgot I have a YouTube video if interested in watching. It can be found here
https://youtu.be/VbcydxsNRUQ

 

[Doofy]

Good job! Perseverance paid off, finally.

 

[alwaysFlOoReD]

 

[tomw]

Would it be correct to say that there's no temperature gauge sender located on the side of the block, above and rearward of the oil filter location? If it's re-located to the thermostat housing, then there should be nothing, a plug, or an un-bored spot where the sender used to reside in older models.
I have an old truck that has a temp light instead of a gauge. It started to come on irregularly, and to my mind there was no reason for overheating. I checked under the hood when it came on, and all seemed normal. I got a NOS sender, and installed it. I tried to do it with the coolant in the block. Bad move. Big mess. Installed and all is well, but it was disconcerting to have the light come on whenever it wanted, no rhyme or reason involved. Part prices were all over the map, and some were beyond reasonable. I think if you find a part, and quit looking, you can easily pay a lot more than should be a proper markup. Thirty or forty dollars for a sending unit is too much, unless it is made with a lot of unobtainium.
tom

 

[beech2000]

I wonder why the 98 model 2.5's have gauge sending unit installed in the T-Stat housing? Especially if coolant leaks out then the temp gauge goes to zero but the engine overheats ... >??@Q(*&(_*&!@*

Both a cluster idiot light from block mounted sender along with the gauge sending unit would be nice