K guys still need help. Prior i replaced tstat and heater core valve. I have replaced temp sending units on tstat housing and on block. I replaced rad, cap, wtr pump, hoses maybe 8 mos ago.

When i fire up rig temp guage climbs clear up to 230ish mark and i have to turn on heat to get it to come down. It now stays between 200-230ish and bounces pretty quickly back and forth, takes a couple seconds. My heat is also mediocre at best.

Heater core plugged (why my heat is bad)? Air pocket (sensor in block reading air temp inside instead of coolant)?

Any help greatly appreciated guy. Thx in advance.

 

New fan clutch?.....sorry if I missed that.

 

Nope. Hadnt done that one yet. Wouldnt that run me pretty hot? Would that effect the heat?

 

The belt driven clutch fan is the main cooling fan. Fan clutches slowly degrade in performance over time/miles. Got ours at O'reilly Auto Parts, IIRC, about $35 for the Hayden unit. The fan clutch will affect the coolant temp but not the heater performance.

 

Would that good for nothin heater core valve have anything to do w this? I just replaced it before this all started.

 

I would suggest eliminating the heater control valve, that's what the factory did on '97 up XJs. Replacement heater hoses need to be a little longer when eliminating the heater control valve. If u eliminate it, don't forget to plug the vacuum line.

 

Which nipple on heater core goes to tstat housing, which one to water pump, and is one of those lines supposed to be 3/4"? I am eliminating htr core valve and the po ran 5/8" hose on both. Think one is supposed to be 3/4"? Just need to know whick nipple goes to what and which one is supposed(?) to be 3/4"?

 

T-stat housing to lower. Water pump to upper.

 

Ty sir!

 

Well after replacing both temp sending units, tstat again, and fan clutch, it hangs out around 210 then jumps up, tstat opens, it goes back down. Maybe this is normal? Im just mot used to seeing this much movement out of guage. Whatya think?

 

I'm puzzled/baffled, since u've replaced everything in the cooling system........I'm still leaning toward the OE elec temp gauge fibbin' just a little.

With your current ambient temps, it just seems like actual coolant temps would be less than 210F. A properly functioning 195F t-stat should be wide open or very close to it at actual 210F coolant temp. I can't imagine the t-stat getting anywhere close to wide open with your cold weather.

Between the cold air going thru the rad and using your heater, seems like the t-stat would just hover between closed and just barely open, then slowly closing again. If that is the way the t-stat is functioning AND the temp gauge is accurately reflecting that scenario, seems like the gauge would remain very steady just below 210F and not spike up/down.

 

Thats what it used to do. Think tstat is bad? Malfunctioning? It gets warm then drops loke a hot biscuit. Maybe stat is sticking. Not opening slightly but clicking open all at once?

 

I always test stats (before installing) in a pot of water on the stove using a cooking thermometer (yep, I'm weird). I see posts saying throw the stat in a pot of boiling water......that's the last thing u want to do to a stat. Bring the temp up slowly, watching the thermometer and watching at what temp the stat opens. Continue to bring the temp up....the stat should open slow and smooth 'til wide open and close slow and smooth (burner off). No quick or snap open/close movement.

 

So in other words, cook it like a chef, not a short order cook..........

 

Hey, I resemble that. LOL