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2001 Honda Insight Manual Trans 106k miles
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Discussion Starter #1
I’m looking for any ideas or suggestions for this problem I have been having intermediately. While I’m driving sometimes the temperature Gage will slightly increase . It never makes it into the red but it does go up about 20-25%. I checked the coolant level and it was extremely low . I added coolant and it fixed the issue . But when I parked the car and it cooled down , all of the coolant came out of the top of the expansion tank. Repeatedly I’ve refilled it and every time it leaks out the top. Does anyone have any ideas why this happens ? And what are the consequences of me driving the car while it slightly over heats ?

PS -When I received the car there was a cap at the top of the radiator restricting flow to the expansion tank so it makes me believe the previous owner had this issue as well
 

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2002 Monte Carlo Blue CVT
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Read my topic "Shakedown Cruise.". Similar issue discussed. First, I'd suggest you do a proper cooling system burp.

When I see the temp start to creep up, I immediately put the heat on high (90°) and fan on high to draw excess heat off the engine. This drops the temp back to six bars virtually instantly.

My cooling fan comes on at 208.4 ° F which I am advised is within normal limits. I will be replacing my radiator, as I suspect it is original to the car and partially blocked. Parts are on order. You may be in the same boat.
 

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2001 5S "Turbo"
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Please include your Location in your Profile. Need more info on your vehicle. Year, model, Trans, miles on vehicle, how long owned, etc.
Burp directions here:
 

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2001 5S "Turbo"
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5 speed or CVT?
When cold, coolant fluid does not expand.
Are you seeing the level of coolant to the top max. line when warm ? and then when it cools down the bottle is FULL?.
Don't make sense.
 

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2001 Honda Insight Manual Trans 106k miles
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Discussion Starter #6
5 speed or CVT?
When cold, coolant fluid does not expand.
Are you seeing the level of coolant to the top max. line when warm ? and then when it cools down the bottle is FULL?.
Don't make sense.
When cold the container is empty , when it’s hot the coolant is in the tank . Manual trans
 

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2001 5S "Turbo"
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You have a min and a max level line on the overflow bottle. Fill to the max line when cold, get the engine hot and see where the level is., Then let it cool down and the level should be at the min. level. I would burp it properly first. Then get back to us. It should never be full or empty.
 

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Very possibly a bad radiator cap. Probably should replace it. The proper pressure cap should be rated for 1.1 bar.

Scott
 

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I checked the coolant level and it was extremely low . I added coolant and it fixed the issue . But when I parked the car and it cooled down , all of the coolant came out of the top of the expansion tank. Repeatedly I’ve refilled it and every time it leaks out the top. Does anyone have any ideas why this happens ?
Most likely you have a healthy amount of air in the cooling system which should be devoid of air. At a minimum it must be purged, but it will recur if the root cause of air ingress is not found. How the air is getting in is another issue. The expansion tank hack you mentioned might be a clue, maybe not.

I purchased a car with a cooling system problem. There are many possible problems, and some can be subtle. The previous owner's service records showed that at least five mechanics looked at the problem and did not find it. Actually, one got very close but performed the repair improperly and nobody else caught the mistake. The problem? The straw on the cap in the cooling reservoir had fallen into the bottom of the reservoir. The mechanic replaced this with a hard plastic tube that did not fit well and let air get sucked into the cooling system where the straw met the cap. Ever suck soda through a cracked straw? Like that. Since the "fixed" straw looked fine, subsequent work included everything from replacing the thermostat to replacing the head gaskets.

I, too, suspected a thermostat but sure enough the brand new thermostat I pulled out opened at the same time as the brand new thermostat I bought to replace it when I put it in a pot of hot water on the stove.

At that point I searched this forum and read every single post on cooling system failure, and searched the Internet to learn how cooling systems work. Someone else posted about the straw falling into the tank, and learning how the expansion system worked helped me realize that the hard plastic straw was the cause of my problems.

I was then faced with the necessary task of purging the system of all air, which cannot be done through the radiator cap. Honda has a process for it it, it is dynamic, and they don't tell you that coolant may overflow violently and burn you. The only way to stop the process is to stop the engine. Someone else on the forum has been burned doing this. And there are incorrect ways to do it which leave air in the system. So I am NOT recommending you do this work yourself but to have a mechanic do it.

You mentioned issues surrounding the expansion tank. That plastic tank is deceptively modest, but as you may have surmised by now, its proper operation is absolutely critical to cooling system operation.

The tank is essential because coolant expands as it heats. As its volume increases the coolant is allowed to expand through a pressure valve in the radiator cap and into the expansion tank.

Equally critical is the reverse process. As the engine cools the coolant volume decreases and creates negative pressure. The tubing from the radiator all the way to the bottom of the expansion tank must be intact, and have no cracks or leaks, for the coolant to be successfully sucked back in with NO AIR. If there are any cracks or gaps - ANYWHERE in the system - air will get sucked in.

The cooling system must always operate devoid of air inside. Once air gets sucked into the system, it's the kiss of death because air expands a lot more than coolant. Then when the car is turned on, the expanding air will force more coolant into the expansion tank than if there were no air in the system. The system cools; if there is a leak in the system, more air is sucked back in. If enough air is sucked in, the expansion tank may overflow with coolant lost during subsequent cycles.

So mechanics working on these really need to ensure that the cooling system is carefully bled of all air.

The mechanic also has to find and eliminate all places where air might get sucked into the system when the engine is cooling, when the contracting volume of coolant creates negative pressure that pulls in air from places where leaks occurred when the coolant was expanding. These leaks might not be apparent when the engine is stopped and pressure is equalized.

So what obvious things can one look for?
  • Is there an adequate minimum level of coolant in the expansion tank when the engine is cold soaked? If so, does the coolant level rise to a reasonable level when the engine is hot? Or is the level of coolant when the engine is hot excessive?
  • Signs of a coolant leak of ANY size that need to be addressed. In the forum people have reported radiators with tiny leaks. There might be signs of seepage around the water pump which is a sign of a leaky seal. Hose clamps, the radiator, and other areas around the engine and beneath the car should be checked for the sign of a coolant leak. A head gasket leak might not be as obvious. A mechanic can perform a pressure test that can identify some slow leaks.
  • A old radiator cap can be the source of a leak. If a quality cap is bought, one may look at this as preventative maintenance. But just buying a cap without first performing other tests could be a waste of money. The likelihood that the old cap is good and the new one has a problem is small, but something one must consider when throwing parts at a problem without an informed inspection and testing.
  • One can easily verify that the straw in the cap of the expansion tank is securely in place. But they have been known to fall off, and there isn't a recipe for securing them better.
Since you're adding coolant to the radiator, then it's quite obvious that the air purge is necessary. And remember that if a leak exists which is not addressed, air will return and the purge will have to be repeated.

Once a repair has been made and the cooling system is purged of air, the level inside the expansion reservoir should be at the same low point every morning after a long night of cooling and at a similar high point immediately after driving. If the levels are rising over time or the difference between low and high is increasing over time, this may be sign of air still getting in.
 
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Sean,
That is one of the best written treatise that I have ever seen regarding the Insight (any car really) cooling system.

Thanks!

Mods, I nominate Sean's post for stickydom! (Not a word, you know what I mean!🤣)
 
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