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Discussion Starter · #1 ·
I have flushed the old coolant out and replaced with Honda coolant and Water Wetter. However, if I hold RPMs at 3000 for about 3 to 4 minutes, even with a double-core radiator, both fans on and an outside temp of 72F, my car overheats. What else could be the issue?

Ideas:

1) Try bleeding some more.
2) Get a separate temp probe and figure out if it is really overheating and maybe the gauge is just flakey.
3) Check the voltage to the fans to see if they are getting the voltage they need to spin at full speed.
4) How can I tell if the water pump is pumping without losing a bunch of coolant?

Anything else?

Charles
 

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Its not your fans. I am not using any fans at the moment in my car and it runs fine. It may be the thermostat. When they fail, they fail in the closed position, which dosnt let any water through. What engine do you have? if its a d searies, i can help you with that. I would take it to a shop. they could tell you if the thermostat is faulty. PM me if you need any help.
 

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Changing a thermostat is easy, and so is checking it. It's in the thermostat housing (amazing huh?) on the rear passenger side of the motor, the junction of all the hoses. The thermostat itself is on the end of the lower radiator hose. Drain the coolant again, pull the hose and you will see it there. Put it in a pot of water and bring it to a boil, you should see it open just before boiling (180*F). If it doesn't, it's broken. They are $10 new at the most, at any auto parts store. Don't let the car overheat too much or you'll need a new headgasket.
 

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Discussion Starter · #4 ·
I did change out the thermostat a couple of years ago and the lower radiator hose gets hot, which you would think it wouldn't if the thermostat was out. I guess I could take it out to make sure it is opening at 180F. I hate to mess with it if there is something else I should check.
 

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Charles:
I'm beginnig to wonder if you already stated your problem already.
I have seen the gauges or senders poop out before.
I'm not a big guy for just replacing parts,but unless you have a gauge tester this can be frustrating.
First before you go replacing parts.Let me ask you this.During the times that your gauge reads hot are the radiator hoses scorching hot?If not I'd start to suspect your gauge or sender.
If you dont already know the sender is on the head under the distributor.They cant be all that expensive.GL amigo.
 

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Discussion Starter · #9 ·
That's interesting. So the hoses should be that hot? Now what if the water pump was going out? The hoses wouldn't be that hot would they?

I'll check the hoses. Thanks!
 

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As I remember my water pump pooped out on my 1st gen that I used to have , and the hoses were REALLY HOT!
BUT before I start condeming a water pump I'd start with the simple fixes first.
Keep me posted as to what you find.I'll do my best to help.
 

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Engine overheating...

Cause - Solution

Coolant level low - Replenish coolant
Fan belt loose - adjust belt tension
Radiator hose(s) collapsed - replace hose(s)
Radiator airflow blocked - remove restriction (bug screen, fog lamps, etc)
Faulty radiator cap - replace radiator cap
Ignition timing incorrect - adjust ignition timing
Idle speed low - adjust idle speed
Air trapped in colling system - purge air
Heavy traffic driving - operate at fast ide in neutral intermittenly to cool engine
Incorrect cooling system compent(s) installed - install proper components
Faulty thermostat - replace thermostat

My knowledge is based in trees.
 

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LOL go easy on him tom I think hes just repeating a books basic check sheet.
 

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Discussion Starter · #15 ·
Well, I guess it was because I snapped off the bleeder bolt along with part of the housing so I had to screw with it twice already. I just don't relish emptying the coolant again. But I will go ahead and get my lazy butt in gear. Should I go ahead and get a lower temp thermostat considering I am in sweltering Texas?
 

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Here's an old article of mine that I dug up, use what you can or is applicable.
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Overheating can be due to one or a combination of the following things:
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1) See if there is dirt or debris clogging up the radiator fins. This can severly limit your cooling system's performance. If there is, spray the radiator down on both sides with a garden hose and nozzle.
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2) Confirm that the radiator cap is holding pressure. For every psi that the cap isn't holding, you will lose 3.25 degrees Fahrenheit of protection. That means the coolant will boil that much sooner ending in an eruption. To do this, you simply put your ear near it with the engine cold. Open the cap one quarter turn and listen for a vacuum like woosh that lasts 1 to 2 seconds. If you do not hear this, the cap is likely not holding pressure. Another possibility is there are internal leaks. That will be covered later.
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3) Figure out is if the thermostat is opening or not. You can let the engine warm up to normal operating temperature (til radiator fan cycles) then feel and compare the temperature of the upper radiator hose versus the lower. If the lower feels alot cooler than the upper this means the thermostat is not opening. -or- For proof you can see, take the thermostat out and boil it in water and watch for it to open a few moments before the water starts to boil. If it doesn't open on your stove then obviously it isn't opening in your engine. If the thermostat is good, reinstall and proceed directly to the next section below. If the thermostat is found to be bad, replace it with a new one then proceed.

Note* if the fan does not cycle at all, steps have to be taken to find the reason why. Possible causes are blown fuses, pinched or cut wires, bad relays(near airbox), bad thermo-switch on the back of the block, or bad fan motor.
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4) Determine with a simple store bought coolant tester what level of protection you have with the coolant that is in the system. Old or improperly mixed coolant will give you less than maximum protection. For example a 50/50 coolant/water mix will protect from -33 to 225 degrees F. A 67/33 coolant/water mix will protect from -92 to 235 degrees F. Now, if water has ever been added to a system that originally had a 50/50 mix, it's obviously further diluted. Let's say that the mix now stands at 30 coolant 70 water. This means at best, your range of protection is from 3 to 220 degrees F. Toss in that the coolant is old and you can now easily overheat.
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5) Test to see if the waterpump is at least pumping out some flow. Do this by allowing the car to warm up to normal operating temps. With a towel in hand, grab hold of the upper radiator hose and squeeze. While squeezing, reach over with the other hand and rev the engine up and down. You should feel a surge of coolant rushing through the hose with each up-rev. If the surge is very faint or non-existent, the waterpump isn't doing it's job.
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6) Bleeding the system:

a) With the engine cold, top off the radiator.

b) fully warm up the engine

c) open the bleeder screw one and a half turns

d) get in the car and rev the engine up and down between 1000 and 4000 rpm

e) while doing step 3 also repeatedly turn the climate control heat selection from cold to hot. This will help create surges to push out any air.

f) continue doing steps 3 and 4 for a full 15 seconds

g) get back under the hood and close the bleed screw until it is a quarter turn from completely closing.

h) rev the engine a couple times then on the 2nd or 3rd rev, close the bleeder screw and tighten it to spec. 5 or 6 foot pounds is all that's needed. It's also important that you close the screw on the up rev and not while the rpm's are dropping back down. I personally am paranoid that the engine could suck a little air back into the system on the return stroke of the rev.

i) shut off engine and let it cool for an hour

j) open the radiator cap and top off to the brim

That was just my version of the bleeding procedure; following is the rest of the diagnostic procedure.
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Now that you have properly bled the system, see if the overheating problem persists. If it does, look to see that your radiator itself is in good condition. Most, at least 80 percent of the fins should still be intact and in shape, and not missing or bent over flat! If your radiator doesn't pass this standard, it's safe to say it needed replacing anyway. Do so then bleed the system again and see if the problem persists.
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If it does, this is where it may get scary if you don't have much mechanical experience. Pull your spark plugs and make sure that they don't have a green tint to them. Beware of the misconception that white on your plugs means you're burning coolant. The little bit of white or actually off white that you may see on your plugs is a by-product of the ethanol and detergents in pump gas. Don't be alarmed if you see some shades of off white and trust this as it came directly from the guy who trained me the Acura dealership. Of course he may be wrong but I highly doubt it.

Next, you need to check for obvious signs of coolant getting into the oil or oil getting into the coolant. This is indicated by a cream colored milky substance either on the dipstick or under the oil cap. Another tell tale sign of this is a thin oily film on top of the coolant in the radiator. If you find this, it means your head gasket is bad. If you do not find this, it doesn't mean your head gasket is good. Reason is because coolant can be going from the water jackets directly to the combustion chamber then getting burned off and never once touching the engine oil. This could also be happening at such a slow rate that it doesn't show up green on your spark plugs as well.

In this extreme leg of overheating diagnosis, you must first perform a compression test to see which cylinder is affected (where the break in the head gasket is). This break is usually indicated by a compresion test reading on a cylinder that is 30 or more psi lower than the highest cylinder.

Note that just because a cylinder is low doesn't mean the head gasket is automatically bad. It's very possible for the compression rings to be bad or for the valves to not be seating properly.

The ultimate test for a bad head gasket once you've narrowed the problem down to the affected cylinder is to perform a leak-down test. This will require special tools and equipment but I will run through basic test procedures:

1) find TDC (top dead center) for that cylinder

2) with special hose attachment and compressed air, apply air pressure to that cylinder. If you hear or feel air escaping through:

A- the intake, it is because an intake valve is not sealing
B- the exhaust, it's an exhaust valve that is not sealing
C- the radiator cap, it is because you have a break in a portion of the head gasket leading to the water(coolant) jackets
D- the oil cap, it is because you have a break in a portion of the head gasket leading to the oil passages
E- the oil drain plug, it is because there are bad rings or an over-egged clyinder wall
 

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Chenge that stat......

also is the car actually boiling over into the resovoir? or do you just think its hot as per the gauge..... A nice mechanical gauge hooled up to it... would give you an idea of weather it is running at 195 or 240

get that stat changed... it takes 10 minutes and 10 dollars..
refill, blead and post back,,,,

hopefully you did not blow a gasket... there does not have to be water in the oil for the gasket to be bad. that is just one possible scenario

good luck

Chris
 
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