I've been having cooling problems lately, specifically the lower hose blowing off, fixed with a new hose clamp, and the upper hose now ballooning and slipping. I ordered both hoses and will replace them. I also ordered a new radiator/reservoir cap, all from Rockauto.com.

I'm just wondering if the cap actually relieves any pressure when it's overheating? Or is it simply to seal the system up? i.e did I waste the 8 bucks I paid for it or will it help the system at all to have a new one?

 

It relieves pressure by venting to the overflow tank through the overflow hose. The one sold by rockauto is the factory 15PSI setting.

 

What Is the Purpose of a Radiator Cap? | eHow.com

Purpose of Radiator Cap

• Besides keeping water and coolant in the radiator, the cap pressurizes the cooling system. If the water in the radiator boiled when it reached 212 degrees Fahrenheit, it would boil away, your engine would overheat and then burn up. The pressurization and the coolant raise the boiling point temperature, preventing it from boiling. In addition, radiator caps have a relief valve that opens when pressure is too high, which allows pressure to escape through the overflow hose.
  
  

 

It would be a good idea to get an actual temp reading on your engine, either with OBD or an IR temp gun. If you're overheating you need to figure out why.

 

+1

The Expansion Tank (item 1) is under pressure. This pressure is relieved by the Pressure Cap (item 2) allowing excess coolant to vent through Expansion Hose (item 8) to the Atmospheric Recovery Bottle (item 11) behind the wheelarch liner. As the engine cools, the excess is drawn back into the Expansion Tank to maintain the correct level.



The Atmospheric Recovery Bottle is not under pressure. If it fills, the excess vents through Overflow Pipe (item 17) onto the ground beneath the vehicle. This is an unusual event and should be investigated.

The four main causes of blowing cooling hoses off are:

1. sticking thermostat
2. failed water pump
3. faulty Pressure Cap
4. leaking cylinder head gasket

The vast majority of excess pressure issues are due to 1, 2 or 3. Cylinder head problems usually only result from major overheating incidents.

Graham

 

Thanks all! Well I can't see any obvious damage to the cap but I ordered a new one anyways it's only around 8 with shipping. I don't think it's a thermostat since the upper hose does get coolant flow, it was slightly leaking out of it around the new screw on hose clamp I installed.

It's not a head gasket, there is no oil in the coolant and vice versa, no white sweet smelling smoke, etc. The lower hose hasn't blown off since I reattached with a screw hose clamp, but does have a swollen section in the middle where it was bent when it blew off, so I'm just thinking it's an old hose that's worn out and slipped etc, they are the original hoses btw. The upper hose started pulling away and now balloons a bit near the housing. I got the URO parts upper and lower hoses so will be changing all of that stuff later today after it's cooled down.

So once I get the new cap, replace the hoses etc it and if I still have problems at least I'll know it's the pump or possibly the thermostat.

 

I wouldn't completely throw out the head gasket as a possibilty, though hopefully your car is okay. Gas can be pushed into the coolant without coolant going the other way in quantities high enough to smoke or smell. Kits are available to test for exhaust gas in the cooling system if you need to rule that out down the line. Hopefully what you're doing will be the cure. Did the temps ever get checked?

 

I don't have the equipment to check the temps, is there a rental for that at the auto store?

Getting back to the hoses I was only barely able to get the shorter upper hose on. The new hoses are so tight that I had to partially split the one going into the radiator to get it to go on but the split is mostly on the other side of the hose clamp so I'm thinking it will be ok. I'm not going to even attempt the lower hose so I'll probably take it to a shop to have that one put on.

 

Although not the Radiator Hose, the tightest coolant hose I've fitted recently was a new Heater By Pass Hose.

Many will be familiar with 'ballooned' By Pass Hoses:



The replacement looked around one quarter inch less in diameter.



The new one was very tight and there was no way it was going to push straight on.

To fit it, I smeared a little washing up liquid on the inside of the hose all round and for about half an inch into the hose. Offering the hose up at a slight angle and rotating as it was pushed onto the stub made it a whole lot easier.

The same technique will work with the Radiator Hoses.

Graham

 

Hate to admit this here but I just dropped it off with a jag mechanic up the street for testing and to see if he could get the new lower hose on. I just don't have the space or equipment to mess around with this too long.

The system seems backed up to me so it may be a thermostat after all who knows. There was some consistent smoke coming from below the reservoir, not the hoses directly to it, behind the sheet metal that guards the wheel. I just need to get this fixed since it's my only car here so we'll see what the mechanic says later today or tomorrow.

 

In addition to lubrication, warming up the hose well in a sink of boiled water helps in the flexibility department. In that case, lubing the nipples beforehand works a bit better so that no time is wasted from warming to fitting.

 

Hi, got it back, the mechanic did a pressure test and there are no leaks. He got the lower hose on too, don't know how he did it but it's all good now. New radiator cap, hoses and fluid so hopefully that fixes the problem if it's just old hoses and clips.