flow kooler/Robert Shaw thermostat

[N8N_99xj]

can someone confirm the correct part number? I'm getting confused trying to look it up. 1999 XJ, 4.0.

Reason I'm asking is that I had my thermostat replaced maybe 6 mos. ago and it's showing signs of being "lazy." I'd rather just do it myself and use a known high quality thermostat.

Also, would a '94 Grand with a 4.0 use the same part number? Just took the stat out of a friend's Grand completely today because he was running hot.

...and is the Flow Kooler really the best, or what would you recommend?

...and can you buy it at any parts store, or would I have to order from e.g. Summit or Jeg's?

thanks!

 

[Pelican]

I'm just curious what "lazy" symptoms are?

 

[N8N_99xj]

I'm just curious what "lazy" symptoms are?

Just noticed the other day, when I left my friend's shop to go home, coolant temp was up to about 210F by the first stop light, then dropped down to 195, which it hadn't done before. Also seems to heat up more than it used to when I get stuck in traffic, although it's finally been consistently over 60F here so ambient temps are warmer than they have been. In the usual 40-50F temps we'd been having, it'd sit at a rock solid 195-197F all day, it's not doing that anymore.

It has never actually overheated, but it's not acting like I've grown used to expecting it to, and the whole cooling system is new within the last few months except for the water pump which shows no sign of being bad.

 

[sidriptide]

honestly it sounds like you're "over troubleshooting" it.
if your rig actually has an issue that is making it build up heat, you need to find it, rather than throw an expensive part at it.
the world is full of 4.0Ls that run fine with stock water pumps..
check your fan clutch and E-fan for proper range of operation, and make sure your serp belt is up to the task.
start small...

 

[Jeepguy03]

Just noticed the other day, when I left my friend's shop to go home, coolant temp was up to about 210F by the first stop light, then dropped down to 195, which it hadn't done before. Also seems to heat up more than it used to when I get stuck in traffic, although it's finally been consistently over 60F here so ambient temps are warmer than they have been. In the usual 40-50F temps we'd been having, it'd sit at a rock solid 195-197F all day, it's not doing that anymore.

It has never actually overheated, but it's not acting like I've grown used to expecting it to, and the whole cooling system is new within the last few months except for the water pump which shows no sign of being bad.

210* is normal, if it goes 220* or so that is a bit warm, but still within the limits of normal. Since it seems to heat up when sitting in traffic, I would replace your fan clutch, since they wear out every 5 years or so and cause temp creep at slow speeds. It sounds like your Jeep is running fine to me. I would leave the thermostat, and I definitely wouldn't use the flowkooler for a variety of reasons. Sometimes they push too much coolant, allowing the coolant to not stay in the radiator long enough to be cooled. I believe flowkooler is also the pump that is basically just a stock pump with a plate riveted to the impeller, and some have had issues with it coming apart.

I'd start with the fan clutch, and see if that helps. Otherwise it seems to be running normal. The 4.0 is designed to run right around 210* with the stock cooling system. The electric fan doesn't even turn on until the temp reaches 215*. As far as reaching 210* by the first stop light, that is good. That means your T-stat is very efficient and is warming the Jeep up quicker, which will help fuel economy. When you see it drop back to 195*, that is when the T-stat has opened. The cycle will normally repeat while you run the Jeep.

 

[Runnin'OnEmpty]

.......Since it seems to heat up when sitting in traffic, I would replace your fan clutch, since they wear out every 5 years or so and cause temp creep at slow speeds.....

This is true. I replaced my fan clutch and noticed a much
cooler running engine. The temp stayed stable and didn't
fluctuate like it did before.

 

[N8N_99xj]

210 normal for a freshly started engine with a 195F thermostat? I've never seen it before, and I've had it for over two years. Only replaced stat because it overheated on a friend of mine when he borrowed it, and there was no evident cause. had cooling system flushed at the same time. Replaced radiator a few weeks later when I dropped the skid plate to replace alternator and found that the rad was leaking (probably why alt died.) Leak was undetectable without removing skid plate. So coolant, rad, and thermo are all new.

I want to replace thermostat because IMHO it is not operating correctly. I have never seen these temp spikes on a cold start before it opens before the past week or so. I don't know what brand thermostat was used, it was installed by a mechanic who owed me a favor (I really hate doing cooling system flushes, plus we have three different fuzzy critters.)

I do also think that fan clutch may be suspect, but no sense worrying about that until I trust the thermostat. If it's not opening soon enough, who's to say it's also not opening far enough? If after replacing the thermostat it is still running warm in traffic, I'll look into the HD ZJ fan clutch that I've seen recommended.

I don't ever let it get hot enough to automatically turn on the electric fan. Once it hits about 215, I'm turning the A/C on to manually force the fan on. If it still creeps up I roll the windows down and blast the heat.

Serp belt is about two years old, looks great, and is tensioned properly.

 

[Johnnie Walker]

Carquest/Napa replacement water pump.
I recommend a good quality t-stat . drill 1/4 inch holes at 12 and 6. Will continue coolant flow even if t-stat fails.

 

[rockclimber]

Carquest/Napa replacement water pump.
I recommend a good quality t-stat . drill 1/4 inch holes at 12 and 6. Will continue coolant flow even if t-stat fails.

those holes aren't big enough to let enough coolant flow to make a difference if it fails closed.

luckily most thermostats fail open.

 

[Johnnie Walker]

those holes aren't big enough to let enough coolant flow to make a difference if it fails closed.

luckily most thermostats fail open.

Low dollar stats typically do not, better quality ones are supposed to. Some clearly state that they do. But, in all reality, "supposed to" does not mean they will.

Also, why i stated a "premium" or quality t-stat. Less likely to fail sooner than later.

 

[rockclimber]

Low dollar stats typically do not, better quality ones are supposed to. Some clearly state that they do. But, in all reality, "supposed to" does not mean they will.

Also, why i stated a "premium" or quality t-stat. Less likely to fail sooner than later.

agreed.

 

[N8N_99xj]

So who makes a premium or good quality t-stat?

 

[N8N_99xj]

To clarify my previous post. I always had heard that Robert Shaw was the best but they seem literally impossible to buy other than direct from Flow Kooler. Worth it?

Online reviews of literally every other brand are about 50/50.

Or should I just go to dealer?

 

[Lurch]

Mopar, Stant

 

[Jeepguy03]

Mopar, Stant

+1

The only ones I use are Mopar from the dealer or Stant Super Stats. I currently have a Stant Super Stat 195* in my Jeep.

 

[yossarian19]

I've always gone Stant in the past but I've test a few radiator caps out of the box and found them off-spec. I don't know who's any better, though.
I tend to trust Stant and or Gates products. What you get from the dealership should be good, too. Comebacks cost them money so they don't tend to install known BS parts.

 

[Johnnie Walker]

So who makes a premium or good quality t-stat?

Not sure who exactly makes them (my guess would be gates), you could call your local Carquest and ask. But, you want CQ PN: 60209

 

[N8N_99xj]

Well I ordered the Robertshaw one, I'm surprised it showed up OK because they just threw a cardboard box in a padded mailer. No COO listed but I have heard rumors that they are made in China now. Disappointing. But it tested OK in a saucepan so I installed it, also ported my thermostat housing a little. Temp control appears better but sitting still temp still creeps up, now shoots right back down to 195 if I rev the engine a little so I ordered a new fan clutch. Couldn't really tell the difference in rotation resistance between hot and cold so I'm guessing mine isn't tightening up when hot. I ordered the Hayden one listed for the 2.5 engine as I've heard that that is a little more aggressive than the one for the 4.0 for some reason. Looking forward to a summer without watching the temp gauge...

Edit: forgot to mention, after I started this thread I definitely had some thermostat weirdness. Couple times the engine temp dipped below 190F after initial warm up, so it definitely was not responding quickly. Unfortunately I can't tell what brand it is; all I know is that it is stamped "USA" on the top, and "195 A 3178" on the pellet. I also did some quickie DIY "porting" on the thermostat housing, figured it couldn't hurt.

 

[rockclimber]

Why is your engine running at 195 and not 210?

 

[Pelican]

What is involved in "DIY" porting on the stat housing?