........going by your factory dash gauge or an accurate aftermarket temp gauge???????

 

Ok. Gotta get this off my chest. Factory gauge is accurate. It does not read the temp of all the coolant, just the coolant closest to the thermostat. The thermostat is a valve that is held shut by spring tension. A wax filled thermal element in the thermostat opens the valve. As the engine begins to warm up and the coolant gets hot, the wax inside the sealed element expands and pushes the thermostat valve open.

 

The sender for the gauge is at the rear of the head, the CTS is near the t-stat housing.

 

Hmm, retract my statement. Im gonna do more research on this later

 

After market gauges are no more or less accurate than any other gauges. They all operate under the same principles. A gauge is considered accurate if it is within 2-4% of the actuall tempurature or pressure. On a gauge that is reading Oil pressure for instance if the gauge reads 50 PSI the actuall pressure can vary from 46-54 PSI. On a tempurature gauge that reads from say, 100-300 the scale is 200 degrees, 4% of 200 is 8, at 210 your actual temp may be 202 or 218 on a gauge that would technicly pass calibration.

Also, stock gauges use a transducer that repeats to an electronic indicator, there is not gauge involved. A mechanical gauge has a bordon tube, linkage, gears, needle and a scale. A thermometer has a glass tube and a scale, or a fluid that heats up acting on a gauge with a scale that reads in tempurature.

The point of all of this is that after market gauges suffer the same limitations of OEM indicators and transducers but do not ussualy have stringent enough QA. I have literaly seen as much as a 10-20% failure rate on certain brand new instuments that have passed through my calibration bench.

All this talk about after market gauges vs OEM gauges is just talk, if the gauge is broke, it needs to be fixed wether it is OEM aftermarket. If it makes you feel better use both, if your OEM instrument fails, replace it, don't just assume the aftermarket gauge is going to work, they fail too. Every single gauge WILL fail eventually, never trust them, they are indicators only.

 

Found my research haha

 

Nope, certified metrology technician, process control technician.

 

Ok...
Fact: engines run at temps up to 260 degrees ( your screwed at this point of temp) and normally run at temps aroundboiling point for water. They do this because of a PRESSURIZED system. Thats why you have a 18 lb radiator cap on many of the jeeps. Also even the older and newer may have a different style radiator cap but it's still actually a pressurized system. Water won't freeze if kept in a moving container. Only the exterior parts will. Same idea here.

Fact: Auto manufacturers did use " fixed" gauges for a while there when people started to be less interested in what their cars did because we were reaching the point of star wars and star trek mind set and everyone that the next year we would have actual AI's. Ford was really bad for it, but everyone else did it too and did so equally.

Fact: Newer gauges are actually reliable ways to measure the goings on in the car and engine. The sensor for engine temps reads the coolant nearest to it. Not the actual temps of the engine because you the owner would freak out at seeing temps reaching 900 degrees in some spots.

Fact: If you park your car and shut it off the coolant is not flowing anymore and thus cannot do it's job and stops cooling your engine.

Fact: Running a cooler thermostat in a car of a certain age can cause the computer to not go into the correct loop when it should. Mostly we are talking early OBD 1 systems here. It can cause your engine to run to rich or to lean and damage it's own internals. Just like unplugging one will do.

MYTH: No one cares what i have just proven in this post so to me.

Sorry about the long post but just got done reading through my old school books from my tech college.

 

trying to get your XJ to run cooler than it likes to is just a lost cause. they like to run at 210, so be it. save your money and buy a locker or some skid plates or something.

 

Probably one of the most important facts of the how a cooling system works in a vehicle, I have seen people cook an engine, the needle never even reached 180. If there is no coolant in the vehicle, or no fluid flowing then the heat is never transferd to the sensor and passed on to the gauge.

Big hint that there is a problem is lack of heat coming from the heater, but don't worry, the engine will warm things up for you pretty soon.

 

Since this is about heating and cooling, i have a ?? I just bought a 00 with a 4.0 (you know the ones with the 0331 heads that suck ) well this head is still good at this point and im wondering if i ad a 2 or 3core Rad, and a lower temp t-stat, with a flex fan, and a nice water pump to help cool this thing, do you think that would lesson my chances of it cracking or blowing the head gasket...just looking for opinions... has anyone ever put a flex fan on a xj??? Haven't seen it done that i recall.

 

Gentlemen...and Ladies...

The reason your engine runs at 210 or so is because it is engineered to. At that temp the metal the pistons, rings, block, heads, bearings, and other stuff is engineered to expand to a PREDICTABLE size. So, if you know what size the parts will be at operating temp, you know how big to make the parts...so that they work well together and do not bind OR are not too loose. The standard reference point is 212 because no matter what measurement system you use, what language you speak, or which hemisphere you live in, water boils at 212 AND, and this is a big AND, when water hits the boiling point it cannot absorb any more heat - it is maxed out and it boils away into steam and disappears. To avoid boiling away your cooooooolant a pressure cap is affixed to allow the fluid to absorb heat up to maybe 250 or so. This allows fluxuations that are the normal part of varying workloads mapped against slow-to-respond cooling systems.

Finally, another critical element is OIL. The oil specified for your motor is designed to work best at 210 on average. If you cool your motor below that temp, the oil becomes more vicous and does not protect the engine as well. If hotter, it becomes too thin and/or just breaks apart molecularly.

The engine is a SYSTEM. The thermostat, radiator, glycol/water mix, heat range of plug, quality of gas, load on engine (gearing, weight, incline, wind) and all this crap is engineered together. This is why it does not pay to argue with Mother OEM. No kidding...they know way, way, way, way, WAY more we do about these engines. And, as for the argument that MODERN oil is more better for 1987 engines because "it's just more better oil" does not consider that, in 1987, the engine was built with the then state-of-the-art metalurgy and manufacturing using the PREDICTIONS considered standard for oil, heat dissapation, etc. Your 1987 motor might not have the same metalurgy as a 2001 motor and the oil the OEM recommends will be different for this reason.

You can never put this argument to bed because many, many people believe that opinions are the same as facts. That said, IN MY OPINION, if you do not use what the OEM said to use with respect to oil, thermostat, fluid mix, etc., etc., you are doing the WRONG THING.

And that settles it...so let's go get a couple beers.

 

I do not think any of that would help or hurt the head, if your cooling capacity is adequate then adding more cooling capacity is just throwing money away. The temp of the water is what is reported on the gauge, the temp on the head, especially the combustion chamber side is probably about a thousand degrees and a three core radiator isn't going to change that. Not all of the 0331 heads crack, just watch for the symptoms, and look into the hows and whys of installing a pre 00-01 or post 03-04 head.

Some modification is required to install the older head, have not seen a good write up on this but I think there is one out there.

 

Another variable with the boiling point (other than the 18 lb radiator cap) is the fact that OEM specifies a mix of coolant and water, the coolant is an antifreeze/antiboil, in other words it can absorb substantially more heat than water alone, so for those who have gallon jugs of water in their cars, you should have gallon jugs of premixed coolant instead.

I agree, Oil, fluids, tstats should all be changed/replaced with the OEM specified replacements, after all, if the warranty requires it then it should be what is best for the engine, otherwise DC would be paying more for repairs.

 

This says it all when it comes to factory temp gauges. I've had the ScanGauge plugged in the XJ, our Corolla, Saturn and Pontiac and you can see the coolant temp yoyo on all 4. This time of year (summer heat) NORMAL coolant temps will swing 40-50 degrees but the factory idiot gauge sits right in the middle between the C and H, never budges.

The short time I did have the factory 195 t-stat in the XJ (mid-winter) I never saw 210 on the ScanGauge, seldom would see 200.