1999 XJ Cooling Modifications

[hubs97xj]

It seems like the mindset is that if the tstat isn't fully open, it doesn't allow the system to work.

I think the fact that "normal" temps are displayed as 210 (in reality, in the 200-207 range on my junk), which is the temp at which the tstat should be fully open, makes them believe the tstat must be what determines the max temp.

 

[Cherokeekid88]

The BIGGEST improvement that I have made on my jeep has also been the cheapest. about 8 bucks! and that was a 180 degree t stat and gasket.....I have done hood vents, replace parts, purple ice, water wetter, coolant flush, different coolant brands...etc. slapped in a 180 degree t stat last night...drove it today....AWESOME!. I drove it around at lunch...its about 98 degrees here and humid...had the AC on full blast. got up to maybe 200 degrees....working great so far..

 

[notfastenough]

But I'm reverting back to my original question, how does a 180* T-stat make a Jeep Cherokee run at 195* when almost everyone I have ever talked to says their XJ's run right around 210*?


I went through my system about 1.5 yrs. ago. I have a CSF 3 row all brass radiator, a Flowkooler pump, brand new VDO electric fan, 195* T-stat, new hoses, yadda, yadda.... And my XJ runs exactly as it always has. 205*-210*. If it's a hot day and I'm crawling, idling, or the AC is on, the fan kicks on just under 215* and shuts off just under 210*.


If it's possible to swap in an $8.00 part and lower temps by 15* then I'm all over it.... Problem is I don't believe it....

Something I haven't really seen anyone address on the whole t-stat issue: it is simply a bypass valve. Period. It does not "regulate" temperature. Coolant flow through different circuts is the means of reducing temperature. One circut is a heat source, the other a heat sink. When the thermostat is closed (below 195) coolant is circulating still. Just within the engine. AFTER 195, the coolant starts being diverted to the radiator and the temps start to drop providing the heat sink is efficent at that time (air flow + coolant flow)

With that being said, the expectation that a number associated with the thermostat (180 195 etc) is not a real target for end coolant temperature. It sounds like your system is operating quite well as is. However if your preference is to lower the operating temperature, your setup should support lower temperatures. One question though, are you still running the mechanical fan? If so, have you upgraded the thermoclutch?

If you want cooler temps, improve more than just one aspect of the system. You will want coolant to start going across the radiator at a lower engine temperature AND the airflow across the radiator to make it more effective.

 

[wolfpackjeeper]

, water wetter....working great so far..

I am a huge believer in water wetter, not because I think that I minor change in it molecular cohesion is making a huge difference in cooling, but because it goes a long way to fight electrolysis. Kind of a big deal when you have water flowing between an iron block, copper tubing, and aluminium housings, with steel fittings.

 

[Original_MudButt]

it is simply a bypass valve. Period. It does not "regulate" temperature.

With that being said, the expectation that a number associated with the thermostat (180 195 etc) is not a real target for end coolant temperature

Someone who gets it!

Now how do we explain what Cherokeekid88 just said....

I really don't care how many people come on here and claim they replaced their thermostat with a 180* unit and they are running cooler than before. It's not because the thermostat is rated at 180*... It has to be because of some other overlooked factor.

(This is strictly supposition on my part and Cherokeekid88 I'm not picking on you at all, just using your scenario as an example.)

I propose that he not only changed the T-stat but the coolant as well... What kind of shape was the old coolant in? And the old T-stat could have had a problem such as not opening all the way.

(My mechanical fan is original to the truck BTW.)

 

[bigdaddyjlove]

Something I haven't really seen anyone address on the whole t-stat issue: it is simply a bypass valve. Period. It does not "regulate" temperature. Coolant flow through different circuts is the means of reducing temperature. One circut is a heat source, the other a heat sink. When the thermostat is closed (below 195) coolant is circulating still. Just within the engine. AFTER 195, the coolant starts being diverted to the radiator and the temps start to drop providing the heat sink is efficent at that time (air flow + coolant flow)

With that being said, the expectation that a number associated with the thermostat (180 195 etc) is not a real target for end coolant temperature. It sounds like your system is operating quite well as is. However if your preference is to lower the operating temperature, your setup should support lower temperatures. One question though, are you still running the mechanical fan? If so, have you upgraded the thermoclutch?

If you want cooler temps, improve more than just one aspect of the system. You will want coolant to start going across the radiator at a lower engine temperature AND the airflow across the radiator to make it more effective.

Well, I have done several improvements. Better airflow for the radiator, better efan, new radiator,ect....
With all of that, it runs 205 with a 195 tstat, 195 with a 180, and lower, but not consistant, with no thermostat. You can believe it or not, but I see it every day.

 

[notfastenough]

Someone who gets it!

Now how do we explain what Cherokeekid88 just said....

I really don't care how many people come on here and claim they replaced their thermostat with a 180* unit and they are running cooler than before. It's not because the thermostat is rated at 180*... It has to be because of some other overlooked factor.

(This is strictly supposition on my part and Cherokeekid88 I'm not picking on you at all, just using your scenario as an example.)

I propose that he not only changed the T-stat but the coolant as well... What kind of shape was the old coolant in? And the old T-stat could have had a problem such as not opening all the way.

(My mechanical fan is original to the truck BTW.)

For Cherokeekid, prolly went from a worn out oe temp stat to new 180. The t-sat opening that much sooner probably did keep the temps down. That 180 stat is wot at the same temp the oe one is just seeing some movement. No real surprise there. This is of course assuming the radiator, fans, and coolant are all doing their jobs.

 

[carves]

I fully understand that sometimes trail-side repairs require a certain amount of MacGyvering. Gutting a T-stat or removing it completely in order to get off the side of the mountain is totally acceptable. However I don't see it as acceptable to do this on a daily basis

Not trying to say it is acceptable .... but the acceptability of longterm running without a t'stat .... is dependant on the weather and the length of time the engine will be running.

Since its hardly likely that those two criteria will always be suitable - every time the engine is started .... The thermostat levels the playing field by creating a constant minimum warm up temp. After its done its job and is fully open ... Its up to the cooling system to prevent problems.

But I'm reverting back to my original question, how does a 180* T-stat make a Jeep Cherokee run at 195* when almost everyone I have ever talked to says their XJ's run right around 210*?

1/. When ambients and windchill are cold enough to increase the radiator efficiency to its best potential.

2/. When the radiator is so big it "overcools" ... for lack of a better word ... and the 180* thermostat is not fully opening ... because it has to restrict flow to keep the temp up.

The 4.0l typically runs at about 210* as per previous posts mentioning this ..... The 195* thermostat starts to open at 195* and is fully open at 210*

.... and a 1row radiator cools adequately enough to maintain a 210* temp in light load conditions ... in not too hot weather temps ... if all the cooling system components are in very good order.

The 2row rad is slightly better .... but neither are good enough to provide a low enough liquid temp at the rad outlet for a 180* t'stat to play with - to consistently provide an average 195* running temp ...

Theres a few fudge factors to consider ... ambients/windchill, ... cherokeekid88's post ... and even my own situation ....

2row copper/brass with a wider finspacing than stock radiators,
Stock type waterpump,
HD fanclutch,
195* t'stat,
10/90 coolant mix,
Separate tranny cooler ... and,
a little bit of venting happening at the rear corners of the hood ...

.... which provides me a constant ... 195* running temp all year round - give or take a few degrees on the coldest (30*) & hottest (110+*) days.

Yes its a 195* t'stat ... but I was lucky and it behaves like 188*/190* so the next one wll have to be a 190* or a bit less.

a little disclaimer ... No lift or big wheels ... or driving on the rev limiter

Someone who gets it!

Pretty sure everyone here understands a thermostat only sets the minimum temp ... twas one of the reasons I posted that I reckoned this was a good thread.

Now how do we explain what Cherokeekid88 just said....

I really don't care how many people come on here and claim they replaced their thermostat with a 180* unit and they are running cooler than before. It's not because the thermostat is rated at 180*... It has to be because of some other overlooked factor.

Those factors would be weather for starters ... and then - changes from stock e.g. Cherokeekid88 mentioned vents and waterwetter etc.,

... So he needs to list his exact, current setup ... and how it performs under heavier loads ... otherwise the newbs will think a 180* t'stat in a wornout, stock, 1row cooling system ... will perform miracles ...