86 accord very hot....

[jeffcoslacker]

Generally, you start by opening the radiator when the motor is cold, and siphon out about a pint of coolant. Then start the car and let it warm up. During this time, you'll probably see the coolant level start to surge up and down some in the radiator.

When this starts happening, grab the upper hose near the thermostat housing, and watch the coolant. As the thermostat opens, you'll begin to feel a rush of warmth in the hose, and you'll see the coolant begin to move in one direction in the radiator. If you can't see it because the level is too low, add some of the stuff you took out until you can see the flow.

Once the stat is opened, and the motor begins to feel warm all over, rev the motor up to about 2500 RPMs and watch the coolant. It should start moving real fast. After a few seconds to minutes, it'll stop again, as the thermostat closes to retain temp.

This is where it gets kinda tricky unless you have done this alot. If the flow doesn't look right when the revs are raised, and the engine starts going hot, I can usually feel the cold spot in the radiator where the water isn't circulating. This is assuming it is even accessable. (don't stick your hand through the fan to try it )

Sometimes if you wet the whole radiator down with water while it is still cold, you can see when the stat opens, the side nearest the upper hose will begin steaming and dry up, moving across the core towards the lower side as the hot coolant circulates through it. Any cool (clogged) areas will still be wet after the rest dries up.

My advice to you is to just replace the thermostat, it's cheap and very simple to do. If you want a quick description of the job, I'd be happy to provide it.

Once that is eliminated as a cause, you can pretty much assume that you are dealing with a blockage if it still heats up.

One other thing, I don't remember if anyone said this earlier, but an air pocket in the cooling system can cause a similar problem, I didn't think of that earlier. Car will idle cool and may run around at low speed fine, but heat up abnormally at sustained higher speed.

If there are provisions to bleed the system on your motor, try that first. With the motor cold, open the bleeder(s) and fill the radiator. Keep adding until coolant flows steadily from them. Close them up, put the cap on, and let it run to operating temp. Then shut it off.

Let it sit a few minutes, then carefully open the bleeder. If no air is expelled, just a stream of coolant, close it quickly and you are done. If you get some air, open the cap and repeat the fill and run sequence until no more air is seen.

[Deadhead]

ok, here's an update.... my car was just fine on the highway today, no problems what so ever, and i was going 10 - 15 mph faster than before. BUT, it was a moderate day out (approx 70 degrees ) and when it was acting up before, it was a really hot day with a hot wind also. I also started the car with the radiator cap off, and when i put the RPM's at about 2500, it kind of sucked some of the coolant and seemed to be moving, but when i let off, it nearly over flowed.

[Deadhead]

ok, i replaced the thermostat today, and all seems good, idle's better too.
thanks for the help.

[94 Accord]

Did you find out what it is yet?

[Deadhead]

yeah, it was the thermostat, i just replaced it and it's been working fine. i haven't been on the highway with it yet, but when i get on again, i'll let you know.

heh, i just got a lot of coolant on the ground
I didn't think there was THAT much in there lol

[94 Accord]

Thats Good to hear its running better.

[Deadhead]

ok, so maybe it's not the thermostat, i replaced it, bled the system, and it is still not cooling to where it should be. it get's up to 3/4 at the very most, which is better, but i know it's not supposed to get over 1/2.

any more ideas?

[jeffcoslacker]

Backflush the system and make sure the radiator isn't hogged up with bugs on the outside. Did you make sure your air deflector under the car didn't get knocked off?

[Deadhead]

what do you mean by "backflush" the system? and it also got hot like this at idle, so i don't think the air deflector is the problem, the fan's turn on just fine also.

Could this relate to the idle fuel air mixture not adusted right?

[Deadhead]

and with that air deflector, could you post a picture of what it is? i'm good with pictures i just need to know what it looks like.

[jeffcoslacker]

Backflushing is simply flushing against the direction of normal coolant flow, to purge more crud than going with the flow.

Lean mixture causes cylinder temps to rise, but if bad enough to notice a rise in coolant temp, performance would be terrible.

I don't have a Honda, but I could take a pic of one of the other cars, just to show you what I'm talking about. It's usually just a thin ABS plastic strip mounted to the body below the radiator, and directs air up towards the radiator. Cars don't have much grille area anymore, so the deflector helps it move more air through the radiator at speed. Some cars will run hot when moving without it, if it gets knocked off on a parking block or bottom-out or whatever.

Did you try hosing down the radiator when it's at operating temp, and see if you have cold spots (blockage) indicated by areas that dry slower than the rest?

[Deadhead]

no i didn't do the hosing down of the radiator, but i did make some adustments to the air fuel ratio, and i noticed i had a lot more power, and it seemed to keep better temp to. before, when i would let off the clutch, i had to give it a lot of gas to get started well, i think that certainly helped with that. i'll have to see what it does in very hot weather, probably tommorro i'll be able to tell, thanks for the help, i'll keep you updated

[Deadhead]

ok, so i drove the car in really hot weather today, and it looks as though the Thermostat and adusting the air/fuel ratio didn't do a thing.

Ran VERY hot.

I didn't hose down the radiator, but i felt it when the car was very hot, and there were no spot's that were cooler than others

Any more ideas?

[jeffcoslacker]

Ran hot moving, sitting, both?

[Deadhead]

it ran hot while moving, but it didn't get any cooler when standing after i had been moving (such as when i was stopped at a stop light for a while )

When i'm just idle'ing when warming up, it's fine, i could let it run all day without it getting up past 1/2 way.

i looked at the thing that looks like it pushes the air up on the radiator, and it looked fine, but with some scuff marks on it.