Hi guys,

I haven't had time to drive my new C3 a lot after I bought it last week and I might not have any chance this year due to snow. Still, I want to clear things up a bit regarding the cooling system. When I was inspecting the car and took it to a mechanic, he pushed together the big rubber pipe which goes to radiator and told me that the pressure seems perhaps a bit too high but nothing really problematic. We had driven an hour or so before. Today I also checked after running the engine/driving around and it's a bit stiff indeed. There are no coolant leaks, temperature is absolutely fine, no smoke or foam out of the exhaust. The radiator is almost brand new. After I shut down the engine, the pipe went softer in about 5-10 minutes.

If you could somehow describe me how hard that rubber pipe should be after driving?

Also, the engine mechanic of the previous owner told him that he should run the red anti-freeze in the car not the blue or anything else which is usually used on older cars. I've been told by several people that red coolant is only for newer cars. That's the reason I want to confirm if it's okay to use red coolant and whether this could also increase the pressure?

Vette: 1979 C3 L-48 4-Speed Manual

Thanks!

 

What pressure cap do you have on the radiator? The higher the pressure, the harder the hose will be. Higher pressure caps raise the boling point of the coolant water in the radiator and engine. Caps commonly come in pressures from 13 to 16 lbs.

 

I will check what's written on the cap. I was told it's a non-default cap and it has the pressure release handle on it.

 

I think that if you stop listening to these 'bubba' mechanics, most of your (non) problems will go away.

The hose should be hard- too hard and too hot to squeeze with your hand.

The traditional green antifreeze is what you want.

 

Oh thanks, this is some great info! Because on the 5.2 V8 on my 1996 Jeep Grand Cherokee the hose is also rather soft and I thought that all american engines should be like this, also considering what the bubba mechanic said

I will try to find the green antifreeze from some of our shops. I know that we also have Blue available which they recommend on older cars, is it still different from Green?

 

Whatever you do, don't mix the different antifreezes.

If you want to change to the old ethylene glycol green, then you should do a proper flush first.

 

Frankly, I can't imagine why you would change the antifreeze at all, if what you have is fresh. Leave it alone.

 

I just wonder if it's possible that it does some harm to the system if the coolant is the red type?

 

The guy who is able to tell what pressure you have in the cooling system by squeezing a rad hose is the same guy who is able to know tire air pressures by kicking the tires! Neither of these examples would lead me to call the individual a mechanic!

You don't need the newer red type coolant, which was formulated primarily for newer aluminum engine components. Mixing the red with green is a recipe for overheating issues, as the two are not compatible. Stick with the old coolant and let your gauges tell you the condition of the cooling system.

 

The "red" coolant will not harm your engine or cooling system components. It is designed to be 'safe' for aluminum radiators. That is of no consequence if you do not have one. Why throw away $20 to get a different color antifreeze???

 

Over here, the green is best for older cars with brass radiators. Red, orange, yellow, is best for cars with aluminum radiatiors. I've never seen blue here.
Not sure if green over there is the same as green here.
But, it will all work. There will not be a catistrophic failure no matter what you use. Just don't mix different type and flush good befor refilling.
#16-#18 caps are the norm here, but you can go a little bit each way.
I think your jeep hose should be hard also. Might want to check that.

 

As I described in my other thread, I did a lot of driving today. I drove in the city for about an hour and also did some moderate accelerations. Everything was just fine. Then I wanted to try it on the motorway. Just some minutes on a steady 2000 RPMish 4th gear cruise, I had a water cloud around the car and I saw water behind me on the road. I immediately pulled off the road and saw the big coolant hose had become open again from the radiator. With the help of a friend working nearby there, I was able to tighten it again and we also bought some more of that red coolant to fill up what went out from the system. It was some different brand and slightly more neon red than the liquid I poured in there previous time.

The day when the hose came off while the previous owner was driving it, we added new anti-freeze via the auxiliary tank and not into the radiator. However, this time we just filled the radiator all up and started the car. The hose was moderately hard but much softer than on the previous days. I then drove it home, checked again and it was still just moderate (perhaps slightly harder than on my Jeep). I decided to go drive it more cause everything was fine again. I did some full accelerations on an empty road and I checked the hose right after - it was still just about the same moderate pressure.

As hard as the hose was on the other days, it really felt a bit TOO much. It was perhaps almost like a garden hose under water pressure. I consulted with my uncle who also used to work on older cars and he gave me some ideas to think of. He thought that firstly the main reason why the hose came off was probably just because the anti-freeze wasn't transferred to the auxiliary tank at the right time and there was just no other place for the over-pressure to go. He wanted me to find out how the overflow system is done on this car and whether there is some automatic regulator valve between the radiator and aux. tank that could be faulty.

My theory was: because we didn't add antifreeze to the radiator the last time, there might have not been enough anti-freeze in the system and this allows more room for air to be in the circulation. Maybe this can cause overpressure...?

Can someone please give me a few tips where to look and why the over-pressure didn't occur anymore after we refilled the radiator?

 

The cooling system is designed to work at a predetermined maximum pressure of around 12-15 psi. This is controlled by the radiator car which acts as a pressure relief and coolant recovery valve also. It is normal for the hose to be very hard as previously mentioned

The radiator should be filled to the top while cold. Run the engine with the cap off and refill the radiator as required. Stop the engine, refit the cap and then fill the overflow tank the the max hot line. After a few heat/cool cycles the tank may need to be topped up again.

Have you radiator cap checked for function? If in any doubt, replace it.

By the way, if the red fluid is Dexcool, there's many users who have reported long term problems. I would never use it.

 

I will try adding the fluid the way you recommended. Will run it in the garage tomorrow and proceed exactly as you recommended.

How to check the radiator cap condition? I just had a look at what it says on top of it and there's written "330 lbs". Is this the right thing?

 

IMO - to blow the upper radiator hose off you have a restricted radiator core. If it is a new radiator the total flow is to small or if it is old the cores are all plugged up.

The flow path restricts the flow and the upper hose should never feel much of any pressure. In fact the lower hose can colaps from the water pump suction if you didn't have an internal spring holding it open.

 

The radiator is very new, driven one summer I believe. What do you mean by total flow too small? Can it be improved somehow?

 

The type of coolant you use is dependent on the metals in your cooling system. Aluminum, brass, etc. Read the container. I have never had any issues with Dexcool and this is what GM recommends for new engines.

It's easy to check the pressure of your cooling system. Any repair shop will have a radiator cap with a pressure guage attached to it. It's simply a matter of installing the test cap, warming up the car and reading the pressure guage.

 

GM has not built old Corvettes in many many years. What works in new ones doesn't mean it's right for old ones.

 

Your hose blowing off is either due to the clamp not being tightened enough or because the thermostat is defective or installed incorrectly. It is not uncommon to hear of someone installing a thermostat "upside-down"....and that can be a problem. If it happens again, check the 'stat'.

 

His mechanic is right, and anyone who has been around ALOT of engines can tell by looking at a coolant hose (especially if it is swollen up like a pregnant sow) that there is to much pressure in it. Combustion gasses in the cooling system is the first thing to look for, followed by an air bubble. If your upper radiator hose considerably is higher than the top of your radiator you could also end with this.