Here's a pic of my bypass hose which has given up the ghost again ( 3rd time). Seems like when I give the old girl a little bit of stick she blows a pipe. Any ideas on what could be causing this dilemma. When driving normally (sedately) she's fine.

 

Does it run hot if you open up the gas?, I mean before it blows a hose.

It seems likely you have a radiator getting plugged, at high engine speeds the coolant has restricted flow and finds the easiest escape route. Through the bypass hose in your case.

Roger.

 

Very interesting... I am thinking a partial clog somewhere, too. Are these hoses all from the same vendor? Perhaps their quality is lacking? It would take a lot of pressure to blow those if well made.
Is your radiator cap the right pressure and working?

 

How are the head gaskets? They can cause excessive cooling system pressure if damaged. You could get a combustion test kit and check out the coolant if there are no other visible symptoms.

Not saying it is your problem, but it'd be worth looking into, at least for the peace of mind when you discover they're fine.

 

I honestly can't imagine a situation where the cooling system would develop enough pressure to blow a fresh hose in good condition, other than severe overheating, especially if the radiator cap pressure release were working properly.

I would check the radiator cap first, and consider other things second.
If the cap is bad, I would replace it, but still check for possible head gasket or cylinder wall leak pressurizing the cooling jacket.

- Eric

 

Thanks guys. I will start with the radiator cap first and then go from there. Its very annoying as i really cant go on a decent drive because i'm always worrying about blowing a hose.
Cheers

 

All hoses i have used are GM original. I was just thinking about the radiator cap issue. I know that when i refill the radiator with coolant right up to the top, and then after a drive the level is allot lower. This tells me that as pressure builds the cap is releasing coolant. My cars working coolant level has always been about 2" below the top of radiator. I will do a pressure check on radiator and see what happens. I'm not going to think about head gasket or cylinder wall leaks YET

 

Also i noted that in the 69 Chassis service manual ( section 6K-8 Engine cooling ) they talk about different outlet size holes in the thermostat housing in cars with heavy duty cooling and cars without. The bigger the outlet hole the more pressure. Maybe previous owner put the wrong thermo housing on?

 

You're not supposed to do this.

If you look in your owner's manual, it tells you that the proper fill level is about 3" below the edge of the radiator filler, lined up with an embossed line and the words "FILL LINE" on the side of the radiator.

If you overfill it, the excess will come out.

However, the system should not be able to produce as much pressure as you've got if the cap is working right and you don't have a combustion chamber leak.

- Eric

 

Does the engine run hot before the hose lets go?.
If you have head gasket problems you would have other symptoms like emulsified oil from coolant contamination, and it would develop the same symptoms if you drove gently, might take a bit longer but the symptoms would still manifest themselves.

Does the radiator have cold spots?, what other symptoms do you have?.

The more information you give us the better we can help.

Roger.

 

But, if he's got a hairline crack in a cylinder wall, which is small enough to act as a one-way valve, letting hundreds of psi of combustion chamber pressure out, but essentially no coolant in, his oil might be clean, and it might never show if he just idled it. This could also happen with a head gasket leak that was "just right," though it's less likely.

- Eric

 

True enough, I came across this on a Rover once. But the coolant smelt of gasoline and had a small oil film on the surface.

Roger.

 

BUT... He still hasn't told what his coolant, oil, and exhaust smell and look like . Wouldn't be surprised if it turns out exactly as you said.

- Eric

 

Hi guys. Thanks for all the thoughts. I work away from home on a rotational basis. So when im home next i will try and diagnose some of the things suggested. I'll get back to you.

 

I would think the radiator cap would pop-off with major pressure. Are the heater hoses connected or blocked off? Have you changed your thermostat??

 

I found out the hard way how much pressure can build up in a plugged radiator with a 68 Roadrunner I had many years ago..... The car was running hot , and I tried to add coolant to the radiator via removing the cap and pouring it it... needless to say the entire system emptied out quickly onto the underside of the hood which was all the way open..... to this day I still cant figure out how I escaped injury , and I actually seen someone get burned this way , and all the skin peeled off their hand... never had a hose blow from pressure , just boil over into the overfill jug

 

Yes, an overheating radiator can do some real bodily harm, extra caution is always suggested when removing the cap on a warm or hot engine! I've seen the same scenario but on a face!

 

I haven't done anything yet as im still not at home. when i get back I will start with the radiator cap to see if its OK then the thermostat and test it in some boiling water to see if its working, then probably go and take radiator off and get it professionally cleaned. Oh yeh i might do a pressure check on the radiator as well before i take it off. I friend of mine has some equipment that you attach to the radiator filler that tests to see if you have a leaking head gasket or other internal problems. So i'll let you know what the results are when done

 

The same pressure tester should also be able to test your cap.

- Eric.

 

Does the car have a temperature gauge?, if so you can easily find out if the thermostat is working by opening the hood and waiting for the radiator to suddenly get hot as the gauge nears normal operating temperature from a cold start.

Roger.

 

Yeh have the gauges but not installed yet. Only the, what do they call them (poor mans gauges). I have tested the temp after a drive with a laser temp tester and it looks normal, around 88 to 90 celcius.

 

You said these were original GM hoses... How old are they? All from the same lot I wonder?
Take a look in the splits on each of them (if you have them) and see if there is split cord material in the split area. If so, and pull on them with pliers and see what kind of tension it takes to break them. If not, there is part of the problem.

The only hose I ever had burst was a cheapie no-name brand lower radiator hose on my Ford. Engine was normal temp (195), just a bad quality hose. I have used Gates or Goodyear since with no issues and replace them every 10 years.