Matts2k87

I was driving along, 60 mins into a drive and I look down and the car is on 1 bar of heat. Then comes good, then cools down again. Thermostat you's reckon?

Jpmelfi

Sounds like it, I had a similar problem in my 94 accord.

Chance S2K

Yep, sounds like an intermittent problem with your thermostat.


I'd definitely get it fixed soon!

Car Analogy

One overheat instance could easily toast your motor. So be very careful and vet this fixed asap. Not something to wait and fix later.

Matts2k87

Thanks guys. I havnt driven it since i noticed thinking it was a thermostat. Never seen them cool a cars temp down like that before though. Just had a bit of head work done so thats the last thing i want. Will be buying one today

Car Analogy

Could also be air in the system. If it goes full cold quickly, that might make more sense.

It can be tricky to bleed the air from this cars cooling system. Look for the billman diy. Try that first. With the issue you have if its air its likely to be a lot of air. So if you do this and you get any air at all,go full tilt aggressive on getting every bit of air out, and see if that alone cures it.

If not, go for the thermostat ( then rebleed again after that).

Matts2k87

Have now bled the system, had a couple of bubbles come out but not many, replaced thermo and thermo gasket, and the problem still remains. When I idle the car for a while it seems to stay on 2-3 bars of heat but then I go drive it and it drops down to 1-2 bars. The choke will come on and it will carry on like a cold motor even though its not. It started wanting to stall out from a stop start, and the car was sort of labouring up until 3000rpm. VTEC cross over is not as aggressive and it doesn't pull like it should.
Also, I was having problems with the cars idle last month and had the same problem happen again when I returned home from the test drive. The idle was going from 1500rpm to 3000rpm about once every second and a half. I cleaned the sensors in the manifold bolted to side of intake and it made it a little better but ended up replacing with a good 2nd hand one to completely fix the problem.
A friend told me its defo the thermo sensor either at the dash or under the hood. Apparently, he says, if you undo sensor and earth it out on the block, the temp gauge will either go right up or do nothing. If the bars do rise the sensor under the hood is stuffed, or if it stays still the dash cluster is stuffed? My mate is pretty good with cars usually but I wasn't too sure about this. Can any body confirm this to be true? Or is there another way to check which of the sensors is playing up? Or any other ideas of unrelated reasons this could be happening? Thanks guys

Car Analogy

I think you still have air in the coolant. It can be very difficult to bleed these cars.

Your mate is saying the temperature reading on the gauge doesn't match reality. That the engine is really warm, but the gauge is saying cold. Either because the temp sensor in the engine block is bad, or the gauge itself is bad.

But lets first confirm the hypothesis that gauge reading doesn't match reality. Its soooo easy. Is the coolant very hose hot to the touch, the top one going to the radiator? Turn the heat on high, does it blow so hot out of the vents it almost burns your fingers? (Obviously both these tests are done after engine has been running long enough that it should be fully warmed up.)

If you don't have both hot hose and hot heat, the problem is the coolant, not the gauge reading.

If the coolant is not getting hot, STOP DRIVING THE CAR. You will melt your motor if you aren't careful here. Like I said, I think you still have air in the coolant.

Matts2k87

Both hoses are warm to touch but they are not to hot to hold. Pressure in top hose feels pretty spot on, and coolant is getting warm and cycling properly. Heater has always been toasty warm so i can't notice it being hotter than usual. I've had 2 different brands of coolant in it aswell so that couldn't be the problem. I've talked another mate of mine (licensed mechanic) in to coming around tmoz to check it all out for me. Ill get him to bleed the system properly for me.
I'm really thinking coolant temp sensor though, is it true that if you earth coolant temp sensor on the block, the temp gauge will tell you its stuffed by rising all the way up?