Water temperature

[wemooz]

I have an ERA 427 with a 428 CJ. My fan thermostat switch failed and I had it replaced by a mechanic who has a good reputation (he works on Jay Leno's cars). The car now runs at 200 degrees or over, with or without the fan on. I have cracked the temperature sensor on the intake manifold and it bleeds coolant, so it appears that there is no air bubble there. Any suggestions will be appreciated. Bill

[Zoom This]

More info needed. Did the mechanic drain coolant from the system to change a fan thermostat? How hot did the motor run before? Does the water temp stay at a constant 200 degrees when idling for long periods of time without the fans running? Does the motor stay at 200 degrees while driving on the freeway?

Bill

[Rick Parker]

The switch may have been replaced with one that is set to fuction or close at a higher temprature.
Before the switch was changed, did the fans come on at a lower temprature?

[CHANMADD]

He put the wrong thermostat in. Change it for a 190 degree one.

[wemooz]

The thermostat was not changed, it was the switch in the lower radiator hose that activates the fan. The correct switch was installed, and the coolant was changed at the same time because in order to install the switch, the lower radiator hose needs to be removed. So the only things that were done were to remove the lower hose, replace the defective switch, and change the coolant. The water temperature now runs up to about 200 degrees, but will go higher if the motor is pushed - as high as 230 degrees. The fan now operates properly, but it does not seem to affect the temperature. I hope that this clarifies what was done.

[ERA 778]

Sounds like you still have air in the system. Do you know if there are 1/8 inch bleeder holes in your thermostat? It sometimes takes a lot of patience to get all of the air out of an FE. There is also a bleed valve located on the top (passenger side) of the radiator that can help getting the air out as well.

[wemooz]

Thanks. I thought that this might be the problem, so I cracked open the upper radiator air bleed and coolant came out, so I closed it. Then I did the same thing with the temperature sensor that is on the intake manifold and coolant also came out. I don't know if this is positive proof that all the air is gone, but it is what I did. As far as bleed holes in the thermostat, I do not know if there are any there. But my car is number 290 and I have had it for 21 years without this kind of problem, and it has the same thermostat in it as when it was new. Is it possible that I still have air in the system? If so, how can I get it ll out?

[patrickt]

Originally Posted by ERA 778

Sounds like you still have air in the system.

Yep. On FEs, getting the last little bit of air out can be a nuisance. I've had good luck by parking the car with the nose up at a nice angle, run it so it gets hot, and then loosen the petcock on the top of the radiator that ERA puts on there, close it up, and then loosen the water temperature fitting on the intake manifold, and then close it up. Hopefully air will come out by doing this. Then loosen a hose at the heater at the firewall -- sometimes air comes out here and sometimes it doesn't -- I don't know why. Drive the car, then repeat once more and you should be good to go.

[ERA 778]

If you've had the car for that long and never had to disturb the cooling system, it might be that just by coincidence the thermostat has decided to "retire" at the same time as the fan switch. Might be worth the trouble to go ahead and swap it.

Make sure you get the right replacement unit. I learned last week that I had the wrong one in mine - bought one for a 68-70 FE at first, needed it to be for a 63-64. The older ones are larger in diameter and correctly fit the recess in the expansion tank flange.

[jhv48]

If the fan coming on doesn't seem to effect the temperature, then your thermostat is defective.

When the water is hot, touch the radiator hoses. Are they good and hot too? If not, then the thermostat is not opening. Or, if warm, but not hot, then the thermostat has one or more 1/8 inch holes drilled in it that are letting some water flow though not enough to adequately cool the engine.

Do the air purge thing first. Then, if no change, replace the thermostat.

[Michael C Henry]

Did you or are you using a thermostat with one or more small holes in the thremostat disk? Have you eliminated the original thermostat bypass hose.? I recamend keeping the thermostat bypass and a thermostat with one or two small holes. I had a brother-in-law that had a 84 F250 with a 460. It kept blowing all the coolant out ofv the coolant recovery tank. I found thet the short hose inbetween the intake manifold and coolant pump had an internal blister that closed off the bypass flow when hot. The blister was not visable from the outside but when that short piece of hose was just removed the inside was allmost closed off. So I reccamend keeping the original thermostat bypass system so coolant keeps circulating in the engine block.
The small holes are allready installed in some thermostats. they let the air circulate out of the coolant system and don't really affect the flow so the thermostat can better sence the coolant temperature and open and close . Another FE trick If you are using the original large diameter thermostat style it has a large body and a small valve to let coolant go to the radiater. Chrysler products have a direct relacement that is large thermostat to fit the pocket in the FE manifold and uses a large valve much like a GM thermostat, but the whole thing is larger to fit the pocket. I have alluminum heads and I don't like the temperatures getting too high. Also if you start getting above boiling temp and the coolant could boil and seperate into a gas like steam and steam doesn't remove heat from the cylinders or head as well as a liquid.
I also use thremal sensors that are in contact with the top of the radiator that transmit to an adjustable switchs and then to relays to turn on the fans. I have four sucker fans, the two at the top are wired together and the two lower fans are wired together. I also have a bypass switch on the dash to take manual control before things get out of range. Keeping the car moving is the biggest part about keeping temps where the thermostat is actually set.
Also my car has the widest radiatot that could fit up in the nose and has a lean back the top. I have to lower the radiator out the bottom

[Bill Bess]

Bill, you might want to start with a few basic checks. Check the entire cooling system for flow (maybe backflush the block), also make sure there is no water leakage into the engine causing heating to increase. Install a new thermostat w/small hole drilled for a by-pass. Verify that all hoses are good (no collasping when under pressure) causing a restriction. Bleed system for air. If it still runs hot inspect water pump and verify your fan system, sometimes there is too much of a voltage drop which can slow your electric fans. In addition, verify your actual water temp. gauge..they go bad all the time, use an heat gun and a themometer in the water. Good luck.

[mdross1]

FYI Big block Vettes from years ago used to run 220 most of the time running them hard would get near 240.Always sweated it then too and was part of the reason why I converted over to synthetic oil.My 460 Cobra runs at 190 most of the time,running it hard gets near 210/215 with a 180 or 190 thermostat been a while not sure.

[DonC]

I vote for there still being some air in the system if everything was working properly before the switch was changed out.
My procedure is to fill the system cold and then jack the front of the car up as high as I can get it and leave it for about 20 minutes. I can usually hear the air bubbling out as soon as I get the front end up. With the front end still up fill until the level is just about to the separator plate in the expansion tank. Reinstall the cap, let the front end down and run the car through two or three heat cycles. I can watch the temp gauge come up to thermostat temperature, hesitate for a minute or so and then slowly climb to the fan switch temp. At that point the temp will drop back down to near thermostat opening temp and just wander back and forth between the two temp limits. Check the system after each heat cycle and refill or remove coolant as needed.
Don't forget to keep the RPM's up to at least 14 - 16 hundred so the water pump is working at a level sufficient to circulate the coolant. If you're careful you can leave the cap off the expansion tank and watch for coolant circulation as the temp gets near the thermostat opening point. Once you've verified circulation recap the tank and continue through the fill cycle.
DonC