You release coolant pressure? Never a good idea to do that regularly.... First, pressure is what keeps coolant from boiling in the first place. While your average engine temp may not exceed the boiling point of coolant, on the gauge, that certainly does not mean that there are not areas around the engine that exceed that. So pressure keeps the coolant from boing and thus gassing out. Second, one thing that can cause boiling is a side pressure drop, even if the coolant temp is not at boiling. Also that sudden drop could shift coolant around and push air where it should not be.

The upper hose should be hard under operating temp - again, pressure. When cold it is generally easier to squeeze. With expansion tank off, of course very easy.

With that said, you could get a pressure gauge for the system. Most simply involve swapping out the expansion tank cap. And if you have not replaced the cap, maybe you should. OEM only from a reliable seller, cheap parts are horrible and tons of fakes out there. Hoses should be dry fit only, not full of coolant or even contaminated with dry coolant.

 

I replaced the tank a few months ago, the original had begun crazing and finally split open, and it came with a new cap though sometimes it's hard to remove or it doesn't click when putting on.

Yes, the upper hose's hard when hot and in use and pliable once cooled. The idea of releasing pressure isn't anything I've ever done on this truck or any other vehicle, I made the assumption relieving pressure might help with the amount of hoses and seals that've been failing.

I've not observed any boiling. My concern's what caused a 2.5 year old radiator plastic to split open from top to bottom, and in consideration of the number of bit's which've failed in just these past few months, water pump o-rings which were replaced a couple of years ago, intercooler pump, and some other hose fittings or is this all coincidence and bad luck?

Another concern's that I actually drove 3-4 miles like this, but in upper 40s at night. ECT remained normal despite cooling loss but I'm concerned about the sudden loss of pressure and coolant and any possible affect to the head gasket or do you think with the cold temps and distance, etc it's going to be ok?

Still waiting on a new radiator, was supposed to be here yesterday.

 

You will not see the boiling, that is not the point. It can happen, it would be inside the cooling system at the engine where it is the hottest. You won't see it in the expansion tank, too cool there.

And yes, driving AT ALL with coolant loss is a really bad idea. Because once the coolant is gone/discharged/etc you are no longer getting proper engine temps since the engine temp sensor sits in the coolant path. Also if a hose came off, then you are no longer really circulating coolant anyway - the flow path is broke. So once enough is out the pump is just moving air and now the coolant is just sitting around the block boiling away causing the engine to super heat.

I think step one is to look at the cap and see what pressure it is rated for. Make sure it is OEM and not some cheap knockoff. Pressure caps are a critical component after all. I have seen some people with LR3s put LR3 expansion tanks on their vehicles not realizing the LR4 cooling system operates at higher pressures, then they have issues like you. So I would investigate the cap, replace it would be best and consider getting a coolant pressure gauge setup. Then if pressure is getting too high I would start to consider blown head gaskets, etc. The engine is an air pump, so depending how the gasket fails it could be pumping exhaust or combustion air right into the cooling system - but again, the cap should protect from over pressurization. But it should also come on/off easy. I almost wonder if it is the wrong cap - again, for example, the LR3 and LR4 caps are not interchangeable since the threads were changed a little on the tank - but the cheap aftermarket ones always have them messed up.

 

I don't recall which vendor I purchased it from, it was over $100 and genuine, I think, isn't much more. The tanks looked identical side by side but the cap's certainly aftermarket. The LR4's 30 PSI? Like I said, I don't even know if there was ever too much pressure, it's the number of casualties recently and now this very large split, perhaps 8 inches down the side of the radiator.

Sorry, should've clarified, what I meant by boiling was I've not HEARD any boiling under normal operation. I did have boiling when I was having issues vacuum filling after the pump replacement a month ago.

I'm aware of the issues with driving, but it was cold, in the middle of the night and I was almost home and I never imagined it would be a failure like this.

So finger's crossed all's well and hope it's all just a bunch of defective parts and rotten luck.

EDIT:

Found it, it's from Dorman... Cap's rated for 200kPa

 

Well Dorman is a brand I personally avoid at all costs, but that goes back years for me. And certainly not genuine tho, a Dorman tank with cap is about $45 USD so guessing you did not may over $100. Or so I hope not. Again, not saying specifically the cap is the issue but the cap should be the weakest point of the system when it comes to pressure and it seems like you are over pressurized. Wish there way a way to test the cap but all I can think would be to remove the tank, plug all the ports but one and pressurize with air. I suppose you could take it to a shop. I think what they do is pressure test the system in reverse. Meaning on a non-running engine they pressurize the cooling system with air and see if it leaks down. My concern there is that coolant could be pushed into a cylinder. One can also do a compression test and leak down test of the engine itself to check for head gasket leaks. Anyway, think ya just need to investigate further. I agree that what his happening is not typical in any case, OEM parts or not.

 

Actually I paid just over $100, in stock at neighborhood AutoZone, not available at main dealer, needed it right away. Genuine wasn't much more costly, but not available August last. Picked up a new cap from the main dealer and there's a night and day difference. The genuine part feels stronger and rattles, the Dorman cap make no noise and feels cheap. Fitting the genuine's quite different as well, loud, positive clicking and easy on easy off, Dorman never clicked. Wouldn't surprise me if the Dorman didn't function correctly.

Spoke with a radiator specialist and they said replace the thermostat (global back order) and plastic radiators commonly fail even after just a few years.

I am familiar with leak down tests etc. FIngers crossed it doesn't come to that.

 

Nissens replacement fitted, few hundred miles done and no further issues. And of course new genuine expansion tank cap. For those who may need to change the auxiliary intercooler pump as I've done a couple of weeks ago, turns out removing the fan and upper and lower shrouds which takes a mere 5 minutes, allows the pump assembly to be removed in minutes from above. When I replaced mine it took me a few hours working from below and above, cramming my hands and tools to remove hoses, etc. Wish I'd known this then!

 

Update if any further issues please.

 

Well, everything has appeared to be working ok for the last 3 days and several hundred miles, ECTs seem to varying between 196 F to 218 F whilst driving, no idea if this's normal or if the temps should remain more stationary.

However I am quite paranoid about the upper radiator hose, it's extraordinarily firm and quite expanded in the middle compared to it's smaller diameter at the radiator fitting. Surface temp of the hose measures 187 F when driving.

After sitting with the bonnet open for 5 hours, the hose was cool but still fully firm and swollen. Normally when cold it's soft and consistent in diameter from one end to the other. I decided to open the reservoir cap and release the pressure and the hose returned to normal size.

Then I noticed a new leak, from the lower inter-cooler hose. I replaced it within the past 2 years and was in good condition when I reattached it in the radiator replacement.

 

After leaving it sit for several days without driving, the upper radiator hose remains hard as a rock. I can say with certainty this was never the case previously. Even after a few hours, the hose would be soft enough to squeeze. Seems to be air tight, so to speak. So what's the correct status? Soft as it used to be or hard even when cold and sitting for days?

Fixed the lower intercooler hose with a worm clamp, seems these OEM spring band clamps don't last long as this's the third one in a year.