marylou

hey, i got a D16Y7 coupe, '98. here's the problem: radiator boils almost instantly and it overheats.

what i've done: put in a new thermostat. it did not solve the problem. there are no coolant leaks. the radiator is also in good condition, doesn't look like there are any cracks or anything. it's also fairly new.

what does happen is that after it overheats the top radiator hose is hot and the bottom radiator hose is very cool. no water is going through there at all.

also, the radiator fan doesn't turn on. this leads me to the conclusion that the next logical step would be to change the ECT switch. i don't know much about all this stuff, but the ECT switch controls when the fan goes on, right?

OR, a more expensive conclusion would be that the water pump isn't working, because that lower hose isn't getting warm/hot at all.

but really, could it just be the ECT switch? let me know what you guys think. if the ECT switch is the problem though, would that even affect the fact that water isn't going through that lower hose?

thanks for your help!
-emma

HondaPartsHero

http://www.techautorepairs.com/overheating.html

rickyracer

maybe your radiator is clogged... loosen the bottom hose and run water through the top hose..if alot of water pours out the bottom your ok..if it starts to over flow and not much coming out the bottom replace the radiator...

Former User

Unplug the 2P connector to the fan switch on the thermostat housing and then short the two terminals in the wire harness connector with a jumper wire. With the key in ON(II), does the fan now run continuously? If so, check whether the running fan prevents the engine from overheating. If not, try bleeding the cooling system of trapped air. If the problem still persists, you may have a clogged radiator, as mentioned:

marylou

okay, i will try that this evening, thanks. so it doesn't sound like the water pump is an issue to y'all?

this is very helpful also, much appreciated.

Former User

Rule out the obvious simple possibilities before considering a bad water pump.

Briman2021

How fast is "instantly"? I have had a coolant sensor go bad so the fan wouldn't go on, but it would only overheat after about 5-10 minutes of sitting in traffic. Does it overheat if you drive around and have wind flowing through the radiator?

I would definitely check to see if the radiator is plugged and the coolant sensor is working, but if it is overheating as quickly as it sounds, IMO that would point to a head gasket as that is the exact same symptom I had when I had a blown head gasket.

marylou

instantly = turning car on and driving a couple blocks. no traffic, just up and down the street.

i thought white smoke was indicative of a blown head gasket? there's no white smoke coming out of the car.

tried to change the ECT sensor yesterday but the damn bolt wouldn't come off and it got dark before we could finish. also, how the heck are you supposed to reach that drain plug by the oil filter to do the flush?? it is so tight back there. i know it's possible, but jeez. compact cars are a pain sometimes.

rickyracer

the drain plug is on the radiator....not by the oil filter...

marylou

yeah i know...but isn't there another one back there you have to open up to drain?? at least that's what my helms manual says.

Former User

You don't need to remove the drain bolt on the rear of the block for this purpose. In fact, draining the coolant may not be necessary at all. Just bleed the system afterward.

Deetz

Rads are cheap! Put in a new one. You old one probably looks fine, but they due get clogged internal after time, especially if you don't do rad flushes every couple years...calcium deposits build up

B16B4NG

You can open the radiator cap and after the car has warmed up see if the water is circulating. Obviously you just replaced the thermostat so that rules it out.. from what you posted it looks to be the water pump or some kind of clog in the lines. When was the last time you replaced the pump and how many miles on the car?

for a blown head gasket just check your oil to see if it has a wierd milky-ness to it and that would indicate you have a bad gasket. But that's high unlikely given your symptoms (no white smoke)

marylou

about 150,xxx on the engine. oil doesn't have that milky look to it. i don't know when/if the pump was replaced..just got the car a few months ago. the radiator was replaced a few years ago. would the water pump have been replaced with the radiator? ehh. i have some old service records from the previous owner in the glove box but the damn thing is stuck and i'll have to break it to get it open.

we'll see if the coolant sensor was the problem though, replacing that today. because the fan isn't coming on at all. hope hope hope it's not the water pump but we'll see!

Deetz

^^ Your fan SHOULD come on when it gets hot, that is why it is there!

marylou

what controls the radiator fan? what is it wired to that makes it come on? because it does not come on when it gets hot, i know that it should...i thought that it was the ECT switch that made it come on, which is what i am changing out.

sorry i am also confused. like i said, don't know a whole lot about these things.

Deetz

check your thermoswitch

B16B4NG

if it has 150k miles on it the previous owner should have done a timing belt change and along with it replace the water pump.. if he didn't then i say you replace the water pump anyways since you'll likely be doing it in the future. and no the water pump isnt replaced when the radiator is replaced.. theyre both in two different locations. Water pump is replaced when the timing belt and tensioner is replaced
Even if the fan comes on if the water isn't circulating that would be pointless, but if it isnt coming on, then somethings fishy there...
check to see if the water's circulating, and if it is, then yes check that thermoswitch

AGENT_47

This+1

any mechanic worth 1/2 their weight in gold always replace the water pump when doing a timing belt change, or at least suggest doing while in there

marylou

timing belt was changed about 60,000 miles ago. since the service records are still stuck in the glove box (i know, i'll break it open soon), i can't say if the water pump was also changed but i am fairly certain that it would have been.

if i end up having to replace the water pump i'll put in a new timing belt at the same time.

so the thermoswitch is the same thing as the ECT switch? if this is true then that is what i am replacing.

Deetz

Look, people are giving you advise and forgetting some of the facts.....

If your fan is not turning on, there is a problem! That would have nothing to do with the water pump or circulation of your rad....get your fan looked after 1st, it should activate at a certain temp

marylou

^^ yeah, okay. there is a fan problem. if the fan is not activating at a certain temperature, something is wrong with whatever controls the fan. what controls the fan? like i asked before, is it the thermoswitch/ect switch???

thanks

B16B4NG

Remember what his symptom was though? he said the bottom radiator hose was running cool which means the thermoswitch (ect sensor) would not be able to gauge the higher temps since the thermostat/switch is located where the bottom hose ends.. this would mean something is getting clogged, or the pump is not operating effectively..

but anyways, you should check all three.. SEE IF THE WATER'S CIRCULATING. It's only takes a minute of your time

the sensor should be located on the thermostat area

marylou

SHE

marylou

thanks for all the feedback, will be checking all the above.