Need some mechanical advice...again :)

[rodhx]

Okay folks...I really hope this is a stupid question & I'm just being over-cautious, but here goes (posted this on miata.net too):

I just completed a laundry list of tasks on the miata getting ready for the upcoming season, including the waterpump/timing belt replacement. Buttoned it all up, refilled the radiator, and let it idle for several minutes with the cap off waiting on the fans to come on & the thermostat to open so I could top it off. That never happened and eventually the radiator was overflowing so I turned it off and went about other tasks.

Yesterday, I took it out for 2-3 miles shakedown run. When I got back the rad cap was lightly steaming and the overflow tank was down to the min mark. Only noticed the steam because I had a flashlight out checking for oil leaks. Top off the overflow tank again.

After work just now, I checked the radiator (full), overflow tank was full, so I let it idle for several minutes. The fans never came on, the steam reappeared from the closed cap, and the top radiator hose was hot...not scalding, but hot. Water temp "gauge" was in the middle of the range.

Now I'm at a loss and afraid to drive it. The fans are plugged up, the belts are on, and not sure what to think now. Am I over-reacting or does it sound like something is wrong?




Thanks!!

[engled]

Turn the A/C on and see if they come on.

[rodhx]

I'll try it. A guy on miata.net suggested parking it nose up and run it with the cap off so it will "burp", so I'll look at that also.

UPDATE:
thanks Darryl. I forgot turning the ac on forces both fans on. that was a quick confirmation that they are indeed working. Took it outside where I could park it pointing uphill, burped the lower hose by hand for a while, then let it run for about 15 minutes. The air now seems to be out of the system and the fan cycled on several times, so I think I can relax now

[edtype1]

First, did you replace thermostat & RAD Cap? If you haven't in some time then you should. Seeing steam coming from Rad cap can be a sign of a bad cap. I always bleed the coolant system by turning the defrost on heat @ full fan speed & letting it idle for about 30 min. I've always had success using that method. Have your cooling fans kicked on? If not, remember to check temp sensor, fuses and relays and make sure they're not blown & working properly. Hope this helps...

[zukitek]

The cooling system has an air pocket in it and is not full yet. The fan comes on at a very high temp (sometimes as high as 220-240 degrees). By this temperature,your cap needs to be on since it is near boiling on an OPEN system.

Your filling process is flawed . Do not leave the cap off while you run the engine and dont drive it untill you are sure its full .I have had cars that I have had to run untill warm and then shut down and let sit then fill the radiator and again and then ...."repeat as necessary"

At work,i have a funnel that holds almost a full gallon of coolant that screws onto the radiator just like a cap so its sitting there waiting for the gravity to flow it in .I realize this is not present in the average garage but it is a very affective tool .

Think of it like this .A dry pump will not pump.Untill the cooling system is totally full the pump cannot be efficient .Temp guages dont register accurately when its not coverd by water .Fans dont come on when the sensor that turns on the fan arent covered completely by water etc.etc.Long story short...keep filling it ,keep cranking and running it for short 10-15 minute increments and refilling in between untill it is full and operating properly.
RR

[rodhx]

Thanks for the additional advice guys. I think I'm finally close, but I'll give it a coupla more reps to be sure. I probably do need a radiator cap. Thermostat is only a year old, replaced when I put the radiator in last year, but I don't remember replacing the cap.

BTW, since I let it run & "bubble over" with the cap off, I am not convinced that I was actually seeing steam from the cap but rather spilled coolant burning off.

Oh, and I did a little more searching on miata.net. Didn't realize filling the cooling system caused religious debates similar to those caused by discussing lubricants or oil change intervals

[chuck schultz]

If you want some real fun, try doing this with a Fiero - coolant lines the length of the car combined with an engine higher than the top of the radiator - frivolity ensues.