Since I changed the radiator and water pump, before that it never went beyond the 210 mark

 

Don't know about the '88 FSM, but nowhere in the '98 FSM does it say 210 is, or reference to 210 as being "normal operating temp". Most factory temp gauges do point +/- the middle of the gauge (just like the XJ when all is normal) but then most factory temp gauges just display a "C" and "H", not a number in the middle.

Verify factory temp gauge with a temp gun or scan tool and verify rad cap function by noting the rise/fall of coolant level in the bottle (motor hot/cold).

 

Just checked the temp with a gun I borrowed from work and at the tstat its just about 95 at the back of the head where the temp sensor is its just about 200 - 210 top so my gauge is definitely off, I did a pressure test on my cap and compared to a brand new one off the shelf and it was the same so I'm now back to square one.

 

Not sure why there would be a 100+ degree temp difference from the front of the motor vs the rear????.....seems strange.

The rad cap is a 2 way valve......it has 2 valves with-in it...... one releases pressure (motor hot) the other opens (motor cold) to allow coolant to return to the rad from the bottle. They work independent of each other. Only way to check coolant return valve is to note if coolant level drops in the bottle when the motor is cold.

 

Oops didn't notice that I meant 195 lol long day

 

The level was dropping until the other day, I just thought of something that if I'm right I'm gonna kick myself, when I went to firestone I wonder if they filled my coolant and went overboard

 

Ok just called firestone and they do top off so I'm hoping the guy went overboard and added a little more than necessary, maybe tomorrow I'll try to pull a little out and see if it stays down

 

Check the level in the bottle after it has sat for 8-10 consecutive hours not running. Level should be no more than 1/2, no less than 1/3.

 

It sat overnight last night didn't change hopefully by tomorrow

 

I have the closed system but I had a caprice with the open system and if there was too much coolant there was a spillover in the resevoir where coolant would come out when the engine got to operating temp and had too much coolant. I don't know how the resevoirs are on post 91 xjs. Like djb said, coolant level should rise in that resevoir when car is hot and drop when cold. Your temp readings are right on though, 195 is perfect at thermostat and should have a higher reading at the back of the head since the coolant is flowing to the back just like you have. If your level doesn't drop I would suck a little out.

 

Coolant flows into the front of the block, to the back of the block, up to/thru the head and out the front of the head. Coolant enters front low, exits front high.

T-stat does one thing only.....control minimum coolant temp. The other cooling system components, their condition, along with ambient temp and driving conditions determine max coolant temp.

 

k so coolant enters through water pump and exits through thermostat? If the coolant is still traveling through the entire engine and hits the back of the block thatcoolant temperature is going to be higher than the coolant entering the front of the block because it has traveled through the entire engine?

 

Yes....had to read it a couple times but yes lol

 

Yes, the coolant that enters the front of the block is the coolest and coolant that exits the front of the head (after traveling thru both the block and head) theoretically would be the hottest.

When u say engine, that would mean both block and head together. All of the coolant enters the engine via the front of the block and all of the coolant exits the engine via the front of the head. Coolant is always flowing/circulating thru the block and head via the coolant bypass loop (the coolant passage beside the t-stat and the small tube in the water pump. When the t-stat starts to open, less coolant flows thru the bypass loop due to coolant entering the radiator loop. If the motor is running, the pump is constantly circulating coolant into the front of the block, throughout the block/head and out of the front of the head, regardless of coolant temp and regardless of the stat being open or closed.

 

It looks like it went down a little before work this morning, really hoping it did, if it was a little over the full line I wouldn't care but that was like half a gallon extra. I'm gonna be driving with my heat on for a while until it goes down, try to get it circulating as much as possible.