Seamoan

So ive been out of state for three months and i had arranged for my old man and brother to drive my car around so that its not just sitting. about 2 weeks before i returned my dad told me the 7 over heated and he had it towed home to play it safe. anyway i drove the car and it was fine. checked the coolant/oil they were both fine. on my way home the car overheated but the gauge was bouncin up to way high then back to the normal spot. i drove the car home parked it let it cool and started taking it apart. i checked the fan by turning it while the car was off it did not move freely. so i pulled the radiator out and ran water through it. the water came out clean. so i pulled the water pump off and wouldnt you know it looks perfect. my last resort is to check the sending unit but id like to learn more about this thing before i mess with it. how often do these go bad? what are the symptoms of a failing sending unit? if anyone has some information about the temp sending unit ill be very grateful! (also if ur gonna say the R word plz just keep it to yourself :\

clokker

iTrader: (2)

Checking the gauge sending unit was the second thing you should have done.

The first would have been to start the car and see if it was really overheating or the gauge was simply lying to you.

But, since you've already gone to all the trouble and eliminated the other suspects, the sender is the last logical culprit.

Basically, the sending unit is a variable ground for the gauge.
Your "bouncing" gauge would point to either a failing sender or a frayed wire/bad connection between the gauge cluster and the sending unit.

The sender is easy to replace (I can't recall if the oil pressure sender must be removed first) and only about $25, probably what I'd do first.

Seamoan

Okay thanks. One more question I should have asked: will a faulty temp sending unit cause the car to actually overheat?

AGreen

iTrader: (11)

If it leaks so badly the coolant loses pressure and causes boiling, but electrically, no. The sending unit is only for the temp indication to you, not to the ecu.

RotaryEvolution

iTrader: (30)

the coolant temp senders rarely fail, they may get corroded and give false readings but i have never seen one spike due to a faulty sender. it is a grounded/resistance sender system so if that wire rubs through and grounds anywhere on the engine or chassis the gauge will read full hot.

Seamoan

i have to rebuild the engine then?
rad was ok
water pump was ok
car actually overheated

RotaryEvolution

iTrader: (30)

i wouldn't go that far, what other signs are there that the coolant seals are going out? it could just be the wire grounding out on the engine somewhere.

Seamoan

what wire could be grounding? when the gauge read hot the there was actually steam coming from the engine bay and the coolant was boiling over. also idk if this is just a coincidence but when the engine overheated i lost my brakes. i had to ebrake. that was odd. the reason i think its the motor is because the other cooling components seemed fine

RotaryEvolution

iTrader: (30)

if it's boiling then yea, it is running too hot. just wanted some verification that it is in fact running hot.

did you check the thermostat and pressure caps? top off coolant level?

mali_FC

same problem here, I've even pulled out the thermostat...and same crap.

now a dumb question Seamoan.....hows your exhaust? do you still have cats on?

cloughed cats are the only thing I can think of that could cause the engine to run a little rougher and heat up faster....

AGreen

iTrader: (11)

Overheating only at idle- fan issues
Overheating only while driving - blocked airflow, no cooling panels (mud in radiator?)
Violent overheating, boiling, puking - bad coolant seal. This can be tested by running it with the radiator cap off before it heats up. If it's bubbling before it get's hot (within about a minute), then you've found your problem.


A bad water pump is unlikely, but a thermostat can stick shut, especially if it's not an OEM thermostat. I've never had overheating problems because of the coolant system not being burped properly. I have, however, experienced these problems with other makes/models (GM 3400 series, some hondas, etc) but not the FC. Generally, if the overflow tank is filled properly, a couple trips should take care of the bubble.

mali_FC

"Violent overheating, boiling, puking - bad coolant seal. This can be tested by running it with the radiator cap off before it heats up. If it's bubbling before it get's hot (within about a minute), then you've found your problem. "

+1

Seamoan

Thanks guys. I recently changed the thermostat in august. It was oem from rx7store. My exhaust is stock. Ill do the coolant bubble test I've done it before but I'm not sure I knew what I was doing. My next move will be to pull the cats off and get the rad cleaned out.on a side note I have always kept the coolant level where its supposed to be. Ts jiffy lube coolant and the rad cap is new as well.

mali_FC

let us know what was the problem once u fix it