91Pioneer Posted July 21, 2023 Share Posted July 21, 2023 What should my temp be after driving around town for 20 mins on a fairly warm day? It seems low, I think the previous owner put in a lower temp thermostat (the truck came from FL) I bought a new 195 thermostat to put in and flush the coolant, hopefully I’ll get to that next week. Link to comment Share on other sites More sharing options...
ghetdjc320 Posted July 21, 2023 Share Posted July 21, 2023 Check your temperature with an ir gauge or similar at the thermostat housing just to verify the reading at the dash. The 4.0 fuel map is tuned for a 195 thermostat. Link to comment Share on other sites More sharing options...
91Pioneer Posted July 21, 2023 Author Share Posted July 21, 2023 My truck seems to run rich it seems all the time but I’m not sure how it’s programmed for closed/open loop if that’s based on time or temp. I can check that. Link to comment Share on other sites More sharing options...
gogmorgo Posted July 21, 2023 Share Posted July 21, 2023 That’s where my 2.5 sits on the gauge. Only climbs higher when the crack in the block lets out enough coolant that it starts overheating. It’s a slow leak, takes six months to a year to get to that point. Even after confirming a new thermostat was opening at the right temp. It was right at 90°C on the thermostat housing when I checked with both my crappy tire IR thermometer and the Snap-On thermal camera at work, right at 195°F. I tried a couple different sending units I had laying around and it didn’t change anything either. Link to comment Share on other sites More sharing options...
TurboedMJ Posted July 22, 2023 Share Posted July 22, 2023 My truck has been doing the exact same thing, except at 150f. When I pulled the t stat housing off the head and found that the stat was bent open (not sure how) which was letting too much coolant through, causing my truck to run rich and trying to warm up but never getting there. Replaced the t stat with this and it seems to work fine. MotoRad 2000-195 High Performance Thermostat https://a.co/d/2qlGcDV Link to comment Share on other sites More sharing options...
91Pioneer Posted July 22, 2023 Author Share Posted July 22, 2023 I used my IR gun and checked a few spots at the thermostat housing after a 20+ min drive. It was 181*F to 192*F so I guess the thermostat is doing its job and might just be the right spec. The gauge is incorrect I suppose. Link to comment Share on other sites More sharing options...
gogmorgo Posted July 22, 2023 Share Posted July 22, 2023 I'm not sure I ever actually tried a known correct sending unit, now that I'm thinking about it. My 2.5 originally was an idiot light cluster that was replaced by the PO with a full cluster, without changing the sending units. This may partly have led to me replacing the original engine with one out of a YJ, and I would've had a spare YJ engine to pull the second sending unit from that I tried. I also had a couple 4.0's sitting around that would likely have had an XJ sending unit but I don't know if I ever tried one... think I tried to get a new sending unit but wasn't sure what to get and don't think I ever did end up getting a new one. I also kinda suspect there may be some scale buildup at the sending unit, insulating it and preventing it getting an accurate reading, but I've never investigated that either. Definitely wasn't a priority. Link to comment Share on other sites More sharing options...
JeepSchmidt O'Guinness Posted July 22, 2023 Share Posted July 22, 2023 The sensor in the thermo housing is for aux fan. The temp gauge sender is at the rear of the block next to the map sensor. I would suspect that sender is bad before fireing parts cannon at the gauge. Link to comment Share on other sites More sharing options...
91Pioneer Posted July 23, 2023 Author Share Posted July 23, 2023 I noticed that while cranking only the temp gauge spikes to the top and then comes back down once the engine starts. Is that a clue? Next up I'll clean off the sensor connector with brake cleaner and see if that helps. Given the relatively cheap cost I may order the temp sensor next time I'm ordering from RockAuto. Link to comment Share on other sites More sharing options...
91Pioneer Posted July 23, 2023 Author Share Posted July 23, 2023 I cleaned the connection with brake cleaner, it was clean but now it's super clean and tight. The sensor is more $ than I was expecting but I'll probably still replace it at some point. I wonder if I could take it out and scrub it with a scotchbrite pad and put it back? Hmmm.... I know the coolant itself is almost all water and rusty so yeah.... I do plan on replacing the thermostat and flushing the coolant soon anyway. On 7/22/2023 at 9:04 AM, gogmorgo said: I also kinda suspect there may be some scale buildup at the sending unit, insulating it and preventing it getting an accurate reading Link to comment Share on other sites More sharing options...
gogmorgo Posted July 24, 2023 Share Posted July 24, 2023 Drop it in some CLR or something, maybe… if you can even get it out in one piece! Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now