Well the topic says it , been scratching my head for days now.i know the topic has been killed but I'm desperate. 99 civic dx ls swap b18a temp gauge crawls up when idling for a long time / driving in traffic / low rpm then climbs back down after I put her in gear.. while coasting or at highway speeds temp is running cool no problems (yes I know ram air) Anyways first thing first checked the fan , comes on when temp gauge hits 3/4 , replaced the fan switch on the thermo housing anyways why not... ok did nothing so I checked the rad for leaks , hoses , etc no leaks but there was no coolant in the overflow weird just filled it up recently but rad was full nonetheless. On to the next I pulled out my thermostat it was cooked (literally) swaped it out for a oem honda one.. didn't make much of a diffrence tho. Ive been staying on top of the coolant it doesn't seem to be burning or leaking but where did the coolant for the overflow go.. hm I bled out the system via bleed nipple until there was steady stream still nothing . To top it all off "winter is coming" (GOT) hehe and I have no heat , the blower seems to be pumping cool air.. could this be related to my problem? Any thoughts guys? Last thing I can think of is bad water pump or blown hg...

 

Bump

 

Heater doesn't work (when it did before) means there is a bubble of air in the system. Bleed air thoroughly by running with the radiator cap off with the car parked facing uphill. Heater temperature dial should be set on full hot during this process. If you keep getting air in the system after every trip, head gasket is likely blown. If you start the engine cold with the radiator cap off and rev it, there should be no action in the radiator. Bubbles or coolant gushing out means the head gasket is leaking.

Rule out fan problems absolutely by jumping the temperature switch so the fan runs all the time the key is on. Test drive like that, if it still overheats it is something other than the fan.

 

My good sir thank you for your resourceful knowledge. Yes I did have heat before (no a.c) ofc I will try the hill bleed method but is the bleed valve located by the upper rad hose not the most efficient means of bleeding? I've watched the fan come on once the temp gauge hits bout 3/4 then level out to normal operating temp then back 3/4 and so on if that says anything. I will test the headgasket in the morning and report back.

 

I reved it on a cold start with the rad cap off , rad was topped off , coolant pushed up / level rose .. hg blown?

 

Pull the plugs and look at the piston tops. If one or more are shiny with no carbon or has shiny spots, blown head gasket is very likely (unless it's a newly assembled motor, then the pistons might still be shiny).

 

Update : Jumped the fan switch , car still overheats . When I cracked my bleeder the coolant doesn't come out unless i open it up substantially , restricted flow in the rad? Are there any other things I can look for ?

 

The bleeder screw is just for initial bleeding. Proper bleeding requires running from cold to warmed up with the radiator cap off and the heater dial on full hot.

 

I did that as well , saw a **** ton of bubbles.. ran it till warm but cut it a little short had to head to work. Car seemed to run a bit cooler today but the needle is still spiking I noticed sometimes it literally jumps a little warm back to cold , hot spots in coolant ? Clogged? I am still blowing out cold air , no hot air from the vents.

 

Do this when the engine is fully cold. Take the radiator cap off and top up if necessary. Put cap back on. Squeeze the upper radiator hose and note there is no pressure inside. Then start the engine and rev it while you check the hose again. If you feel pressure build up rapidly, the head gasket is leaking. Pressure should not change until the engine has started to warm up.

 

Pressure does not build up rapidly.

 

As for the pistons looking shiny I'll have to check that out.