Just as the title said my radiator fluid boiling. I have a newer radiator from a forum member that had presser tested good. i have new upper and lower radiator hoses. it has a vent cap. When driving the radiator fluid does not boil in a 15 min run no white smoke. In fast idle it boils in 3 to 4 min throw the radiator vent cap. The car has no temp gauge. and a 165 degree thermostat.

 

how do you know that it is boiling?
what happened to your temp gauge?
how old is T-stat? how old is your radiator cap?
was this happening b4 you got this radiator?
did you install the t-stat corectly?

 

engine was rebuilt about a week ago first drive and my old radiator blow out. (it was the welds across the top). Thermostat is new as of 2 days ago and yes it is installed the right way. The new radiator i have is about 6 moths old. The radiator cap i have no idea i did order a new one it will be in in the morning. The car did not have a temp gauge hooked up when i got it and just have not wired a new one in yet. I think it is boiling there is some coolant getting on the header, i head gurgling, and large amounts of steam in the cooling system Via the hiss i hear around the top of the radiator near the cap.

 

Bad coolant seal on the rebuild? Or maybe even a pinched coolant seal?

 

Is the centrifugal fan working?

 

i don't think it is the engine that has the problem as it had no problems in a test car a 83 for a 45 min drive then it was pulled and drooped in the 79. I found the radiator fluid shooting out of the over flow container. It has a pin size hole on the top of it. this morning after i let it idle for a bout 30 min but no gurgling once i put the new radiator cap on. But still some steam and a little coolant on the radiator hoses near the area where they connect to the engine Right at the fan.

 

Get an IR infrared remote temp sensor ($125 at autozone, $30 at harborfreight, and $20 yesterday at Radio Shack) so you can find where the overheating is occuring and for determining where there might be a blockage.

Trial and error replacement only works for a while.

 

ok i got the IR infrared remote temp sensor. Where do i test for the temp as the hole engine is with in a 10 degree variance. i think it may be a air pocket.

 

Check temp at waterpump, thermostat, radiator hose top and bottom, look for an unexpected temp difference across two test points.

when car is cold remove radcap and start it. let it warmup with cap off. there should be just a stream of coolant visibly moving under radiator neck but nothing coming out. add coolant slowly if it's low. rock car a little and see if some trapped air escapes. have heater valve on to allow circulation . engine should come up to operating temp with no problem.

Is your spark timing good?

 

you said it was leaking on the header, did you install the 2 rubber o-rings between the block and the intake ( assuming that this is a 12A engine)

when your other radiator exploded was it on this fresh rebuild or that the reason for the rebuild? if it was on this rebuild how long did you drive it for before you shut it down ?

 

Drill a 1/16" or so hole in the t-stat to allow air to burp out from that area when the car is started...leave the radiator uncapped while it warms up and top it off each time the level drops...when you see the water level drop in the radiator and can feel warm (or hot) water in there, top it off one more time and then close it up...gotta do the hole first, though.

 

Do you have a Mazda thermostat or an aftermarket one for a piston engine? You have to use an OEM or equivalent. the OEM ones are almost a dual thermostat. They control the passage way that bypasses the radiator. This passageway is open when the motor is cold and closes as it warms up. 165 degree t-stats should not be used on rotaries. Mazda picked the temp they did for optimal performance.

Notice the difference:

^ Mazda

regular thermostat:


See the round disc on the end of the Mazda one?

 

ok i found the problem it was air in the system i will put a 185 t-stat (oem) back in. I got all the air out and it runs beautifully I drove it around for about 35 to 40 min the return hose stays between 195 and 205 depending on the loan after a 25 min warm
up period. thanks for the help guys.

 

check your thermostat
check the clutch on the fan
check the belt for tension it might be slipping
check the water pump
check the fluid
or check for air in the system...