Normal Running Temperature

[Donair]

Howdy.

When I got my XJ (about a year ago) it ran hot. During the warmer summer months, if I was highway driving the gauge would stay at about the half way mark (100?) but as soon as I pulled off the highway into stop and go traffic ... up that little needle would go.

So I put in a new rad. Actually, I had National Rad put one in. That was late August-ish. After the new rad my needle stayed so low it could win any Limbo contest around. I was happy.

What I am now concerned with is that my needle is alway low. I mean LOW ... when it is as warm as it's gonna get, my needle is only a smidge above cold.

This is my first fuel injected vehicle. If the "brain" thinks the block is cold it'll richen up the mixture, right? Like a choke? I'm wondering if since my needle stays low ... I'm running rich all the time which obviously creates problems of in itself. My XJ seems to run fine from the get go. No hesitation or bogging whatsoever whether first thing in the morning or when warmed up. My gas mileage seems a bit worse, but it's winter - I've always found mileage drops in the cold. I have next to no heat in the interior. And I have noticed it might be a tad harder to start when warm.

Any advice?

[sportsguy]

First off - XJ's and MJ's run HOT - your new rad wa s agreat plan.

But, you'll wnat to check the thermostat - the previous owner MAY have installed a cooler stat to cure his "hot" running problem - happens often, so I'm lead to beleive by posting forum chatter.

Anyway, it is possible to "over cool" an engine - at least in theory.

So, After a through check for any hoses that need replacing, water pump ok, etc. my money's on a t-stat which is lower than factory (or maybe even dead already?).

Experienced learned form many a trip to APJ's and the understanding that I AM NOT A MECHANIC and should therefore NOT diagnose problems...LOL

[underwhelmd]

Yeah running cold isn't any good for an engine either. Your mileage would suffer if that is what is happening. But then stock gauges are not exact either so it's difficult to tell...I mean... what real temp is Cold and what real temp is Hot? The only way to tell is a real gauge with numbers on it. Then you would know for sure what you are dealing with. This was one of the best aftermarket things I did to my trucks. You can get an aftermarket coolant temp gauge for under $30.

National Rad (Dartmouth) is a good place for a rad, water pump etc. They have done good work for me too.

But yeah... sounds like you could use a thermostat, based on what you said about low heat etc. unless you have a real reason to use another temp range, it's best to replace with the stock temp thermostat instead of compensating for another problem that should be fixed.

[blacksheepxj]

My XJ runs about a needle width below the 100 mark. It does not matter if it is summer or winter now that I had tha rad replaced. If I am off raoding and putting alot of strain on things then it will creap up to about 1/2 way between the 100 mark and the red. Never any hotter.

Hope that this helps

Rob

[Ken McIntosh]

blacksheepxj said:

My XJ runs about a needle width below the 100 mark. It does not matter if it is summer or winter now that I had tha rad replaced. If I am off raoding and putting alot of strain on things then it will creap up to about 1/2 way between the 100 mark and the red. Never any hotter.

Hope that this helps

Mine also runs at these temps ,have never felt that i was anywhere near "hot" even under the extremes.

[Creepy]

Donair:

you had an old crappy rad, running hot. it blew your t-stat, locking open.

new rad keeps you cool, but rig won't warm up cause t-stat is now wide open.

betcha $10. anyway, throw a t-stat into 'er and you should be good to go.

[Donair]

Thanks for the responses so far. Since a couple of you mentioned it, The Haynes mentions it, they are cheap and easy to replace ... I'm going to throw a new t-stat in there. Thanks.

I am a bit surprised as I always thought a t-stat only affected the time it took to get an engine up to normal temp not the actual temp an engine would warm up to. Also, when I got my rad put installed in the fall I asked the guys to check my t-stat and to replace it if there was even the slightest suspicion of it being pooched. They said it was fine. They also thought the rad they replaced was the stock rad from 250k ago ... what are the chances of me having a stock t-stat in there too ... hehe

Follow up question:

Are there any favorites t-stats (or brands to stay away from)? Mopar? Crappy Tire? Napa?

Oh ... chopshop - I'm not the betting type but I'll buy you a coffee if you (and the others) are right ;D

[jjcan]

It doesn't seem to matter where you get a t-stat a large number are bad from new. So if you still have the problem after fitting it, try another one.
John

[underwhelmd]

jjcan said:

It doesn't seem to matter where you get a t-stat a large number are bad from new. So if you still have the problem after fitting it, try another one.
John

Simple trick: toss the new one in an old pot with water. Put it on the stove. Thermometer in the water. See what temp it flips open.

[Creepy]

i just grab the fail-safe motorads at CT.
have gotten a bad one b4, too.

[itsakeeper]

a bit late to post this but I bought 3 of those Fail-Safe CT thermostats and replaced each after only 6 months; put in a normal one and no probs since

[Sandboxcowboy]

Simple trick: toss the new one in an old pot with water. Put it on the stove. Thermometer in the water. See what temp it flips open.

I learned that trick few years back!! Excellent tech, but god help ya if ur significant other see ya doin it!! LOL

I wont use anything other than Mopar ones from now on. I went through 4 one week from CT. And the Mopar one comes with new gasket!

Justin

[underwhelmd]

Sandboxcowboy said:

god help ya if ur significant other see ya doin it!! LOL

hehe.... note that I said OLD pot. Don't want to be responsible for any marital breakdowns.

It's sad but the things we used to buy at CT to save a dollar on are now junk. Oil filters and thermostats, among other things....better off buying from the dealer and being done with it.

[Donair]

Bad t-stats from the get go ... what a burn.

I went to Crappy Tire on the way home from work yesterday and they had a few options for t-stats; 180* and 192*(O.E.) both with jiggle valves and without jiggle valves.

I'm not exactly sure what a jiggle valve is ... it sounds kinda erotic to me, and come to think of it, I think my wife has one ;D . Seriously, I bought one of each (one with and one without jv) in the 180* range (cooler is better, right?). I can see the little pin they call a jiggle valve that I assume just lets a bit of coolant through even the t-stat is closed.

If a CT one let's me down, I'll dish for the Mopar next time.

Second follow up question:

Does it matter if my t-stat has a jiggle valve or not? As far as I can see there is no mention of jiggle valves in Haynes or FSM. FSM indicates 192* range too ... anyone else running a 180*?

Thanks again.

Oh, nifty trick with the pot. Before we moved into our house, I split dirt bike engine cases in our apartment kitchen multple times. If I was boiling up a t-stat now in one of her Lagostina's today, I don't even think the wife would bat an eyelash ... even if she did all I'd have to do is play with her jiggle valve and it'd be forgotten

[blacksheepxj]

The jiggle valve is there to help bleed the air out of the system. The 192 I beleave is the correct one for the XJ.

Rob