Overheating at low speed

jmw

New Member
Hi,

I'm having problems with my Civic 99 1.6 LS auto.
Everything is fine if I drive in the town. However, problem starts when I drive for a while on the motorway (no problems there) and then go back to low speeds in town - temp gauge is going up very fast at low speeds and when I stop at traffic light. all backs to normal more less if goes to ~2500-3000rpm. Also it seems radiator fan is not kicking off at this point, but somehow works perfectly before entering motorway. next, when I stop (turn off the engine) water transfers to reservoir tank and boils in there. I though there was a fan problem so I changed thermostat and thermo switch but no change at all. I think that maybe: 1. there's an air in the system, 2. radiator cap faulty, 3. some of water pump's blades may be bended and water circulation not efficient, but if it's the case overheat should be all the time not only after motorway drive, am I right?
any toughs suggestions welcomed
 

myknikz

New Member
It seems like there's air in the system..what's the mileage on you're motor?? Maybe head gasket failure also how's you're start ups?? Is your fluid levels okay?? Do you have to fill your radiator every now and then??
 


jmw

New Member
thanks myknikz
mileage is around 155K, head gasket was change around 1.5 year ago and if it was the case wouldn't be some water in oil and oil in coolant? coolant levels stays ok for long if I drive in the town only, but goes very low after long trips - probably bc it boils and splits from reservoir tank.
Will try to burp the system again
 

myknikz

New Member
Who did ya head gasket?? How's ya start up at times?? It seems your head gasket is leaking..try and bleed the system again..take out you're spark plugs and see if you have coolant on top of you're pistons. Why did you have to change you're head gasket?? You really shouldn't be losing any coolant at all..and not all of the time you're coolant and oil will mix unless you're head gasket it blown maybe you're head is warped from previous over heating?
 


RonJ

Banned
At an auto parts store, you can buy a kit that tests for exhaust gases in the coolant. Start there.
 

jmw

New Member
RonJ said:
At an auto parts store, you can buy a kit that tests for exhaust gases in the coolant. Start there.
Click to expand...
don't have it in the UK, unless from amazon or ebay - but it will take time to receive. can buy cheap compression tester from halfords- wouldn't it detect show head gasket failure too?
 

jmw

New Member
myknikz not quite sure what you mean by how do I start up and how it's matter. just standard procedure put key inside, turn it and drive
 

myknikz

New Member
jmw said:
myknikz not quite sure what you mean by how do I start up and how it's matter. just standard procedure put key inside, turn it and drive
Click to expand...
Meaning what does it do when it's starts up?? Does it miss fire and then go away?? Or does if have a hard time starting up??
 

rebirth

New Member
5+ Year Member
It could be something as simple as the cap. I have a 96 ex and mine would overheat when sitting in traffic or driving slow. I changed the thermostat and cap(original honda) and ran water through the system. Still overheated after a few days. Tried to get the air out of the system, and I thought I had it taken care of until days later sitting in florida's traffic. Soon after I had the cap off while running the car, and noticed a few black pieces floating pass the radiator opening. I assumed it was head gasket but it was too flat and thick. I managed to get a piece out, and it was the rubber from the old cap which I hadn't noticed was gone. It took a while to find all of it but once I got it all out, it hasn't given me trouble since.

Other problems you could check is a hole somewhere in one of the hoses. It could be tiny but you have to search for the drips.

Check the radiator for cracks. It could be hairline and barely noticeable, but the effects might be large.

Change the thermostat and cap with original parts. Probably the cheapest original part you can buy from Honda.

Get the air out of the system.

Change the coolant especially if you've been adding water after every overheat. There is probably more water than coolant.
 

xxBLOOD88SHOTxx

Surge Master
Registered VIP
Soo let me line this out

Youre sure you have bled the system properly
Youve changed the tstat and fan switch (fan is working correctly)

Have you physically checked the cap?
You dont have ANY coolant leaks anywhere?


I think best scenario you have a bad cap, worst case your pump is going.
 

biobot93

New Member
I came across this post on google, I have a 7th gen honda that is doing the same exact thing.
I have done the following:
replaced thermostat 2x, and radiator cap
radiator compression test holds 15psi
replaced water pump
compression test reads 180psi across all cylinders cold
spark plugs clean
my start ups are very rough sometimes

no white smoke, no oil in antifreze or vice versa.
tried running with no thermostat, car ran at temp and still overheated. thats before the third one was put in.
 
Last edited:

Bergi85

New Member
I had this same thing happen to my 97 Civic CX. Like your car, mine also was fine around town until I got on and off the highway, it would start to overheat and the temp would spike up really fast, and then come down almost just as fast. I drained the cooling system and didn't notice any oil, and drained the oil and it didn't look "caramel" in anyway, so I assumed no coolant was leaking into the system. But I had to fill the reservoir every other day. I didn’t notice any coolant leaking on the ground when it was parked either. My radiator fan would turn on, sometimes. Later I noticed a very faint white smoke coming from my tail pipe after a hard start.

It was bothering me so much I ended up changing everything in the cooling system
Thermostat (Still overheated)
Radiator cap (Still overheated)

This is when I ordered everything.

Radiator (Yonako dual-core with fan and new cap)
Radiator hoses (upper and lower)
Head gasket
Water pump
Timing belt (I was in there anyways)
AC/ALT belts (Again, I was in there)
Total for everything was around $400 USD and a weekend of my time.

It has been a little over a week now and the car runs great! I'm not sure which one of these fixes did it, but I'm happy it's running right now.
 
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