I have a 98 Civic with 375K, when at idle my temperature rises.....within 30 yards of increased rpm it returns to normal. because of normal maintenance I have recently replaced the radiator Tstat and sending unit for the fan......the fan does come on but it seems like the gauge is showing fairly warm before it kicks in.....Could that be because I'm low on coolant?

For the last 100k or so I would need to add a few oz's of fluid per month.......if it ran low the suction tube in reservoir would start to melt and get sticky. I cannot tell if I'm losing coolant now as it seems like the reservoir overflows while I'm driving? My oil is normal......doesn't burn a drop.....exhaust appears normal....no white smoke or sweet smell.

Thanks in advance for the help.......when I installed the new radiator.......I didn't bleed the heater core or anything would that have make a difference? Is that something I need to do?

Thanks

Rick

 

Have you replaced your radiator cap? check to see if it's worn out..$13 to replace. Is it leaking from water pump, radiator, hose or any other area?..check under distributor as that is a common place for oil leaks (O-ring) which can leak onto coolant hose and cause deterioration.

Also, possible tiny crack or head gasket leak..rent a block tester (free) from Autozone or O' Reilly's and but $9 fluid to test with. Could rent (free) coolant/radiator pressure tester too. Compression test cylinders to find out if there's low compression in one or more cylinders.

 

Yes the radiator cap is new. Just did the timing belt and water pump. I cannot see any leaks. It "seems" as I drive it pushes fluid into reservior but dosn't always suck it back into the radiator

 

Can anyone confirm that I have a bleeder valve.....I'm not seeing it....

Thanks
Rick

 

Coolant in reservoir (over-flow) tank that doesn't get transferred back to radiator during cooling off period is probably the best physical sign of a blown head gasket...especially if you just replaced the radiator cap.
Is the radiator cap OEM?.. there is a definite fitment difference between OEM and say a Stant brand or other OE caps.. the OE's do not fit as well because their curled lips that fit into the radiator opening notches are not as long as OEM's.

Do block test at minimum.. but, best to do compression and pressure test as well... maybe free loan programs have a compression tester to if you don't have one. If it turns out to be a head gasket or crack.. with 375K on engine you'd be probably be better off replacing entire engine than repair..hopefully,, others will chime in with suggestions.

 

test for exhaust gas in your coolant. rent the tool and buy the solution for it.

 

No bleeder valve on '98 Civics. I forgot to mention the first thing you should do is make sure the coolant is burped free of air as best as possible.Then if no change follow other steps listed previously.

 

You also don't need a bleeder valve. Put the front end on jack stands, or on roll-ups, or just park it facing up a hill. Remove radiator cap. Start engine, let it run for 2-3 radiator fan cycles, keeping the radiator topped off in the process. It's that simple.

 

No bleeder valve on these cars.

When you performed the work you mentioned did you properly bleed the cooling system?
When bleeding, do what ^ he said, and have the heat on hot, but leave the can off.

Other than that follow what he said. Air bubbles in the system can REALLY **** these cars off.


if symptoms continue, rent a block tester to see if the head gasket is leaking.

 

Thanks for the help and input. to answer questions.....the radiator cap is a Slant brand.......no I did not bleed the system properly....this time or 120K ago when I did the last timing belt.......yesterday I did let it run for a good time with the heat on but the fan off, I saw online a guy taping a pop bottle to the radiator and filling and letting the coolant expand........So I tried that a lot of air came out at first...........it got near boiling......a lot of steam out of the pop bottle....it still had fluid.....the fan never did come on.....the fan does work and does come on but not as qiuckley as I'd like.....the sending unit is new. I will do the block test.......next week....this week is to full with work and volunteer schedule......I will be driving it Today- Wednesday......I will keep you posted

Thanks
Rick

 

my 96 did the same thing to me turned out the cooling fan switch on the thermostat came unplugged. check and make sure your cooling fan cycles or turns on for that matter

 

Yeah not bleeding the system can create big issues down the road, hopefully you dont have a bad head gasket.

Like it was mentioned before the only way to bleed it is by leaving the cap off like you did, its totally normal to get to boiling, thats how you know it have a lot of air. I am not sure if you have any scanning tool but I recommend that you get a bluetooth obd2 reader for your android or Iphone.. As you can monitor your coolant temps. The fan switch on our cars is set to *204F thats when the fan is supposed to come one. The safe operating temp of the car is 160, the OEM thermostat starts opening at around 170 and the can comes on at 204 which depending if you are idle or moving it will bring it down blow 200F.

I had a similar issue a few weeks ago after replacing the thermostat, forgot bleed it properly, I added the coolant while the engine was running but didnt let it cycle. And I after came here and asked question realized it was all I had to do, removed the cap and let it cycle until the fan came on a few times after putting the cap back on test drove the car and no overheating issue so far.