deposit in radiator hose

I might be wrong here, but I think the cracking would just be the reinforcing inside the rubber on the hose. I dont think there would have been anything that you dislodged into the engine or radiatior. With the constant hot coolant flowing through the hose and the lack of anywhere for anything to lodge in the hose I would be very surprised if there were any deposits in it.
Drew

If your cooling system has a failure you're stuffed. Get the entire system cleaned out and checked by a radiator specialist, well worth the money. Whats the cost of peace of mind against a new motor, tow to town etc

Have you pulled the hose off to look inside to see if there's any residual deposit? Surely if there was any deposit in the hose, a chunk couldn't "crack" loose without leaving some signs that it was there in the first place. Was probably just the hose itself you heard, but a visual inspection would confirm any problem.

At the very least I'd be buying new top and bottom radiator hoses and fitting them myself. Once you've got the old hoses off, have a good look at it/them and maybe evn cut one right open to see what made the cracking sound......could be like the other respondent said above....just the re-inforcing.

On the subject of your temp gauge staying steady even on a hot day.....my recent findings have proved something I have long thought to be true; YOU CAN'T 'TRUST' FACTORY GAUGES. My Patrol's temp gauge was going up on occasions and i wanted to know what the 'actual' temperature was and whether I should be worried about it.

So I've fitted a VDO gauge. The sender/pick-up unit is mounted into a piece of stainless steel pipe I had made up; I cut a piece out of the top radiator hose and inserted the piece of pipe in the hose. The results were quite amazing. From cold start up, my Nissan gauge gets to it's usual position (just below half way) and the VDO gauge is reading around 75deg. When I'm driving, the VDO gauge can go as high as 105deg and the Nissan gauge will stay on 'normal' right through that 30 degree spectrum. Once the VDO gauge goes to about 110deg, then the Nissan gauge quickly starts to move up to just over half way. I am led to believe these sorts of temps (ie: up to 110 deg) still aren't anything to be concerned about. However, the thing that concerns me is that there are MANY Nissan and Toyota owners who have vehicles which have temp gauges that never move off normal. However, i reckon the real story (if they cared to check it and know for sure) would show the actual temp varies considerably. The factory gauges are simply designed to show when something starts to go horribly wrong.

2 possible explanations:

1. Some of the older type hoses had a reinforcing metal spiralled rod through the hose that helped to keep the hose in its natural shape in order to maximise hose volume and coolant flow. If you squeeze one of these hoses you can sometimes feel the metal insert change shape. If they are old enough the metal spiral can break. Just take the hose off and have a look in. Answer is to replace.

2. As the rubber in most hoses gets old it can go really hard and keep shape in a stiff form. If you squeeze an old stiff hose it can feel like it is fracturing or braking. It even feels like you have smashed something inside. It can even be heard as you squeeze it. I have done this and the simple answer is that it is time to change your hoses. It may not leak after doing this however it will reduce the strength in the hose. The answer is replace it.

If you have any doubt about the condition of hoses, thermostats, senders and radiators then you should replace them It is far cheaper than cooking a motor. Flushing out system as per owners manual and putting in correct coolant is also advised to prolong engine life. Cutting corners usually ends up with bigger problems sooner or later.

Hot coolant enters the radiator via the top hose. The coolant loses temp as it moves down the radiator and creates a 'thermosyphon effect" ie it tends to want to fall as it cools and increases in density, thereby assisting the flow of coolant.

This is why it nearly its always top hoses which fail first - the are exposed to much higher temperatures.

There is an Australian made inline coolant filter available called a 'Tefba' www.babymall.com.au/tefba/
which mounts in the top hose. Its amazing what they pick up. Highly recommended.