Coolant boils at shutdown, worry or not?

[VetteOwner]

ok yes while the grill block does yeild higher mpg the whole point of a radiator is to cool the cars coolant.. since yours is 90% blocked its not cooling worth a crap. moving coolant usually doesnt boil unless its in the red zone for a little bit(5 min or sometimes less) and if it gets up there your prolly screwed and already warped the head, and causing some major damage to your engine.

no a higher psi radiator cap isnt goign to help if anythign its gonna make it worse. its designed to relieve pressure so it doesnt blow a hose or the head gasket.

do you live in higher elevations? if you do its automatically more likely to boil over. you may need to adust your coolant to water mix if you do.(more coolant)

and how do you mix your coolant? do you buy the concentrate and then mix it 50/50 in 2 bottles?

[red91sit]

Now that we've got some good ideas to fix your civic, I thought I'd chime in. Those are some really good numbers your getting!

[GasSavers_Ryland]

What you are doing is a bad idea and is going to shorten your engine life, spend the $15 on a fan thermostat, it's differnt then the '92-95, so a newer one will not work, but the upside is that they don't cost much, and are extreamly easy to install, the stock fan thermostat comes on around 196-203F, that is plenty hot.
I had a year long average of 42.2 on my 1984 civic with the same cvcc engine you have without a grill block or anything higher then 36psi in the wide 175mm tires, and I was hauling tools and a co-worker half the time, if you don't destroy your engine by over heating it, you should be able to get better then 42mpg.

[Gary Palmer]

Erik: One of the vehicles our family has is an 87 Honda Civic DX. We have had the car for about 7 years and I have had a considerable amount of experience with the radiator and cooling systems, so I will tell you what I have learned.

The 87 Honda's have a profile which places the radiator very close to the same level that the top of the engine is at. Consequently the radiator, thermostat and fan do not function correctly, if their is any air in the radiator/cooling system. I typically carry a gallon of distilled water with me, and if I think the car is beginning to have any issues, I will top of the radiator when it's cold. It only takes about 1 quart of water, or less, but on that year of Honda it is critically important.

The fan in the 87 does not come on until the temperature gauge is a little above 1/2 way up the gauge. However, the fan will and does come on when you stop the car, if the temperature is high enough. It will run for a couple of minutes, which cools the radiator temperature enough to keep the radiator from doing the boil over routine. Unfortunately, if it does the boil over routine, then it gains enough air to cause the thermostat in the engine to not open as quickly as it should and then it gets into a positive feedback mode, where then engine gets hotter, the radiator loses water, the engine get hot-hotter and so forth.

The overflow bottle which should address a large part of this issue seems to be either inadequate in size or something, because it always seems to be working OK, when I test it.

In any case, their is also a air bleed screw located right above the thermostat housing. If the radiator fill gets a little low, this screw can be loosened to let the air out of the thermostat and head, so that the cooling system will function properly.

My experience is that it is absolutely critical that their be no air trapped in the cooling system. When that is the case, the cooling system works fine and does a marvelous job. If it gets low, at all, it will not function properly. I would stronly encourage you to get the switch fixed or replaced, to operate the fan automatically, and enable the system to run the fan, after you have turned off the ignition and removed your keys, if the system determines that is needed.

Hope this helps you a little. We also have 2 89 Honda's and they seem to have a little more tolerance to the coolant level, compared to the 87. The 87 seems to be sensitive to as little as 1 cup of coolant, so I would recommend keeping an eye on it and keep it topped off.

[GasSavers_Erik]

Thanks guys- I will definitely make sure the fan thermo switch is working like it is supposed to.

Vetteowner- I let the coolant mix in the engine- 50/50. I pour the coolant in first so I'm sure it won't be too weak. Cap- Since the pressure keeps plain water from boiling at 212 F, more pressure = a higher boiling point.

Gary- thanks for the heads up on the air vent on the thermostat housing- I'll be sure and "burp" my car.

Ryland- thanks for the data on your old civic. I was thinking that I was about maxed out at 40 mpg. I'll shoot for 45- I might open up the carb and see why it coughs and sputters when first started in the morning and to be sure my mixture feedback/ o2 sensor system is working right.

[cfg83]

Erik -

Mine seemed to be doing that too. My mechanic replaced the coolant cap. Now, when I pay attention to the coolant temperature, I typically turn on my manual fan radiator switch (love that switch!) near the end of my drive if I don't like the coolant temperature.

CarloSW2

[VetteOwner]

Originally Posted by Erik

Thanks guys- I will definitely make sure the fan thermo switch is working like it is supposed to.

Vetteowner- I let the coolant mix in the engine- 50/50. I pour the coolant in first so I'm sure it won't be too weak. Cap- Since the pressure keeps plain water from boiling at 212 F, more pressure = a higher boiling point.

Gary- thanks for the heads up on the air vent on the thermostat housing- I'll be sure and "burp" my car.

Ryland- thanks for the data on your old civic. I was thinking that I was about maxed out at 40 mpg. I'll shoot for 45- I might open up the carb and see why it coughs and sputters when first started in the morning and to be sure my mixture feedback/ o2 sensor system is working right.

theres your problem...you never mix coolant in the engine for the fact that theres no way to get all the old stuff out. (alot of it possibly a 1/2 gallon or more will be sitting in your block and heater core) that and how do you know your getting 50/50? so you pour in the gallon of coolant and then fill it up with water to the top im guessing...which is usually not 50/50 mix...

yes while more pressure = higher boiling point it also means more pressure on your headgasket and probably worn hoses and pump seals(since the car is what 20+ years old and you say it might have the origional head gasket, is a $800 (give or take) headgasket job gonna be worth the car)... so while yea a $7 cap may fix it it will might lead to costly/timely repairs down the road.

just mix new coolant in seperate conatiners (clean milk jugs even) to a near perfect 50/50 mix and your cooling probs should go away. if not then you know its not your mixture being off.

[GasSavers_Erik]

I hooked up my junkyard fan thermo sensor and it works! (I paid $5 for it and a coil) it is kicking on at about 50% on the gauge. I suppose I'll be nice to my engine and leave it hooked up that way

I'll recheck my coolant mix with my hydrometer. I usually shoot for -10 degrees F (3 floating balls if I remember correctly) which is about 50/50 according to the back of some jugs.

Thanks again everyone.

[JanGeo]

Hey along the same lines I ran a grill block for someof the winter and took it off a few weeks ago and never really disabled the cooling fans but under my hood is a stripe of dried up pink antifreeze sprayed by the water pump alternator belt in my 1.5 year old Scion xB. Just wondering if even a little over heating is going to cause a pump failure from pressure - coolent level is ok.
As far as the fan running after shutdown that is common in most cars that run a little hot as the heat continues to soak through the metal of the engine to the coolent and usually radiator electric fans run for several minutes after the engine is turned off.

[Gary Palmer]

I have never run across anything that gave me any feeling that their was a correlation between overheating and the water pump having any sort of issues. I suppose it could.

What I am extremely cautious of is getting the engine temperature up into the top 20-25% of the gauge. In this area, the head temperatures are up higher, the pressure is higher and it just puts a strain on everything, including the head gasket. I have seen enough to be very confident that their is a huge correlation between letting the engine get up that high and head or head gasket failures which may occur. I do everything I can to get the temperatures back down, including running the heater on High, even though it's hot outside.