hey guys I am new to posting on hondatech however I've been a long time lurker and I've recently began to have an overheating problem with my 98 civic. It's started to overheat these past few days and my overflow tank seems to fill up and squirt antifreeze so I am not sure if I should change the radiator or how to go about diagnosing this problem

 

A free test you can do first, is pull the radiator cap when the car is cold top off the radiator and crank the car up. See if you're getting compression through the cooling system. After this test make sure that the fan is running like it should be. If not trouble shoot that.
If not then you can pressure test the system and see what it does. You can un hook the radiator hoses and see if a pressure test clears out a clog.
If you still don't have anything my next step would be swap the thermostat.

Try those and see what you come up. I started with free stuff and went to a really cheap solution this way you aren't throwing parts at it and you'll have a starting point. Pending these results you can try more advanced diagnosing.

 

Just like Sharpie said. Check your radiator as it could probably be bad. Ive replaced at least 5 radiators in the 3 hondas ive owned. Next is the Thermostat, as it might not be opening up properly. Fans might not be cutting on so check those when your car seems to be overheating.

You may have too much water in your coolant mix. The engine cooling systems on these sohc hondas are truely finicky. Check your water pump as well as it may be over-pressurinsing your radiator and dumping it into your coolant catch can.


-Bam

 

If your overflow tank is filling up and overflowing, [squirt antifreeze I assume means overflowing out of the tank] then you most likely have a blown head gadget.

The water pump can not "be over-pressurinsing your radiator" coolant flows into the overflow tank as it heats up and expands and is sucked back into the rad when it cools down and contracts.

The rad cap keeps a constant pressure in the coolant system, 16 lb on yours I believe, that raises the boiling point of the coolant, a higher pressure cap will "over-pressurize the system, but anything over that point will flow into the overflow tank but not out of the tank, the only thing that will overflow the overflow tank is a blown HG, [or an over filled system.

To check, with engine cold fill system with 50/50 mix coolant/water, leave cap off and start engine and look for air bubbles in the rad, through rad cap opening, if it keeps bubbling, bleed coolant system once all the air is out of the system, let engine cool down and fill rad and overflow tank to cold fill mark, reinstall rad cap and start engine, allow it to come up the running temp., [rad fan turns on] if overflow tank "overflows" you have a blown HG. 94

 

Your thermostat is likely stuck closed.

Replace the thermostat and gasket and bleed the system and report back. Thermostat is about 11.99 and takes about 30 minutes to replace

Head gasket isn't going to push out just coolant, that much blow by from the head would have smoking out of the tail pipe and all other sorts of problems. I've seen a bad thermostat boil the coolant and over flow the resevoir many times

 

I'll definitely replace the thermostat and radiator and hopefully that stops it otherwise I think it may be a blown head gasket

 

If it fails the bubbling in the radiator when cold test you can stop right there, it's the head gasket.

 

Do the other checks I said first. Don't just throw parts at it that's wasting money.

 

Inspect rad cap.