258 running at 230-240. Is this high??????

Hey guys my I just swapped my 180 degree thermostat for a 195 (since
I had my radiator out anyways) in my 73 cj5 with a 258 because I thought it would benefit the new mojave heater I will be installing sooner. With the 180 degree t-stat the motor would not get any hotter than 200 on a warm day and since I switched the t-stat to 195 today it runs at 240 and cools to about 230. Does this seem high? Should I go back to 180? Also another thing I noticed was that even when the motor is running this hot I can still open the radiator cap on this thing. Isn't there supposed to be pressure? And I cant really feel any pressure on the top radiator hose. Please help!!!!! This is my daily driver.

Thanks in advance.

 

Do you have the thermostat installed correctly? Air bubble behind the thermostat?
I run a 195, and run in the middle of the stock gauge, never above, even on over 100* days, crawling uphill. There shouldn't be that much of a diff between 180*/195*.

 

is the t-stat in up side down

 

Yeah, that's too high.
I agree with these guys...you probably have an air pocket or something wrong with the t-stat.

 

Thanks for your help guys. If it is an air bubble behind the t-stat then how can I get it out? I installed the t-stat with the cone out and the spring on the inside of the motor. Is this correct?

Thanks in advance.

 

Like they stated above, drill a small hole in the housing of the T stat. I think you want the hole to the top side of it. At least that's what I did. Where the heck are you that you can get the temp up that high this time of year??? On the way to work I'm not even sure my electric fans kick on right now with the temps in the teens in the mornings.R)R)

I think I'm going to go with a 195 T stat when I do it this weekend. Then when summer rolls back around, I might change to a 180 again.

Good luck


High5

 

Im in payson, Az and its running that hot in 30 degree weather. Wouldn't the t-stat housing leak coolant if I were to drill a hole in it? Isn't the cooling system pressurized? Are you guys saying drill a hole in the housing that the radiator and heater hose hook up to or are you saying drill a hole in the actual t-stat? Sorry Im a little new at this. Thanks for the help in advance.

 

Wow..Payson huh? I used to go there pretty often to get odd ball dirtbike parts from that "all bikes" wrecking yard.
Anyway...they are saying to drill a small hole in the T-stat itself...not the housing. Sometimes you can drain and refill it and make it go away. I have let it idle with the rad cap off until it "burped" and that will sometimes get rid of it too.

 

Don't drill a hole in the housing - drill a hole in the plate of the thermostat. The idea is to allow any bubble behind the 'stat to escape.

IMO 230 is too high. For normal driving, you need some reserve, so the temp should sit right at the thermostat temp (set point) except on the hottest days and under the highest loads. Once you pass the set point, you no longer have any control over the temperature - the temperature will rise in proportion to the cooling capacity and the amount of heat the engine is producing.

First you need to double check your data. Leave the cap off the radiator and put a thermometer down in the coolant. A cooking thermometer will work well. 230 is above boiling at atmospheric pressure, so be careful - if it's really 230, coolant will erupt from the radiator if you remove the cap at that temperature.

You could also measure the radiator temperature from outside with an infrared thermometer. You can get a cheap one at Harbor Freight or such.

 

Put in a new thermostat while you are in there. They often get stuck. Why take it apart twice.

 

Yeah, that's what I meant. In the housing of the actual thermostat. Not the thermostat housing.

 

And you should never be able to take off the cap while it's that hot without having steam erupt everywhere. If you can it sounds like you don't have any coolant in the system. Yes it should be under pressure, and yes, at 240* the coolant will be in vapor form (steam) and it will cook you alive if you try to open it. Steam burns are horrible and not to be taken lightly.

Are you sure the system is full? Can you see coolant in the rad when you take the cap off? If you replaced the t-stat without refilling the system with coolant it would definitely be running hot and would definitely not have pressure when you open the cap.

 

The copper cup containing the wax pellet needs to be inside the engine for it to work properly. The cooling system should pressurize to 15psi according to my shop manual. With my 180 degree thermostat it never its hotter than 190 on a hot day running on the highway.

 

Thanks for the help so far guys. This is a brand new t-stat I just put in. The temp guage is also brand new and only read about 190 tops on a warm day. It is also getting hot pretty fast as if there is hot air at the sender and not coolant. Should I take the thermostat out and fill the motor with coolant from the top radiator hose? When I put the radiator back in there was probably no coolant left in the motor because I had to start it a couple of times without the radiator in there to see if I had fixed another problem with the power steering. Could it be because there is no coolant at the water pump and it cant pump air? Thanks for the help in advance.

 

I believe that so long as the engine/water pump has a bypass route or bypass hose and you topped off with fluid before starting the engine that the water pump is "flooded suction" and therefore not likely "trying to pump air". Also as mentioned do you see fluid when looking into the fill neck? You may need to top off a couple times. And as stated previously be very carefull taking the cap off , water boils at 212*F at sea level if your temp is really 230*F the fluid would flash to steam when the additional pressure provided from the cap is removed by taking the cap off. It is a good practice to check the T-stat function by suspending it in a pot of water that is heated above the T-stats set point to observe the actual opening of it prior to installation, a simple check that will give you confidence in the unit by verifing its integrity.

 

Yes I topped off The fluid many times yesterday and no difference. I also sit there and watch the fluid level and when the temp reaches 240 on the guage and starts to cool a little bit the fluid level stays the same in the radiator. This morning when I drove it it went a little past 240 and started having problems idling and then when it cooled down a little the motor started running better. Another thing is I couldn't tell if it was just coolant I spilled or the radiator cap but last night it looked like steam was coming from the radiator cap but I could still take it off and no pressure. Tomorrow morning I will be working on the jeep and I will try what you guys told me. Hopefully I can find the problem. Thanks for the help guys. Please let me know what you think.

 

Seems like all the problems started after the T-stat replacement...I'm thinking you got a bad T-stat. You may want to also check the calibration of the dash temp gauge but then again... back to the T-stat , no problems untill it was swapped to the higher temp unit if I understand correctly.

 

All your symptoms point to a defective thermostat that is not opening. You can actually remove the t-stat altogether, reuse the gasket and see what kind of results you have. You can also try the stove method to check to see if it is opening properly, but I would just replace it.

It is a good idea to drill a very small hole just above the thermostat assembly to allow the air to escape.

 

The level should always remain constant, it won't go down when the t-stat opens. However, you should be able to see the coolant flowing when the t-stat opens. With the cap off and the engine running from a cold state the coolant should be stagnant in the radiator. When the t-stat opens it will start to flow and you can see the current like a river. I really don't think your thermostat is opening, or at least not opening all the way.