Rad Hose EXPLODED! Need Help Please! Long read.

[slownrusty]

Hi Gang - Check this out! My car was just idling (luckily) on the street infront of the house, I was just returning from visiting a friend (about a 35mile trip). On my way home I noticed that the temp gauge did not budge and was sleeping on the cold peg all the way home, I ran the car moderately (in terms of speed and rpms).

 

Anyway as I pulled infront of the house and was letting the turbo warm down. I was moving my wife's car out of the way and as I walked towards the car, I saw the most massive explosion, looked like something from a movie! In all my years messing, modding and working on my cars and at my uncle's shop, I have never witnessed or seen something like this.

 

I ran towards the car with Carl Lewis like speed and found coolant flowing like Niagara Falls. I jumped in the car and pulled it into the garage immediately and then shut her down. I glanced down and saw that the temp gauge was sitting at around half, which I figured was because there was no coolant flowing to cool the engine, so the engine temps were starting to climb.

 

From my investigation the rad hose erupted with incredible force (pics to come tomorrow). The weird thing was this hose was not on the thermostat side, it was the OTHER hose!! I first thought, faulty thermostat seized built pressure in the hose and caused it to swell to failure. But thats impossible as its the other hose that erupted and is connected to the block with just an aluminum neck and an open port to the block. So how did pressure build so high that the hose would explose with such drama.

 

As an aside, I replaced the water pump last summer due to bearing failure, but I thoroughlly purged 101% air out of the system, I have a neat compressor operated vacuum to draw all the air out of the block and hoses.

 

I am at a total loss guys on this one. Please note that this hose that exploded was only a year old and not an old dry rotting jobbie.

 

So can you guys tell me what you think? I am curious, confused and pants crappy - the three "C"s.

 

I just got back from buying a new hose, new thermostat, and new rad cap, and will replace everything tomorrow and see how things go after I run the car and thoroughlly purge it.

 

Yikes!

 

Yasin

[j260z]

i would have to guess that you had a blockage of some sort. did the temperature guage only start to rise after the big bang? if that was the case then the temperature sending unit was on the cool side of the blockage. i ruined an engine on a neon because i was driving down the hiway one night when the block heater fell out ( i don't know how). because there were lights on the road and i was driving so quickly i never noticed the white smoke or had any smell of antifreeze. to make matters worse the coolant temperature light never came on because the ambient temperature in the now empty coolant passages was hot enough that the guage still read normal.

[Z-Gad]

I tend to think of the worst, and hope for the best...

 

Worst case ... pressure build up due to a blockage in the cooling passages (usually rust or block sealer in the block), or ... water pump came apart inside the front cover, engine overheated due to no circulation, head gasket blew into a water passage and pressurized the hose causing it to blow

 

Best case ... faulty weak hose

[A. G. Olphart]

There is a fair chance that your first guess is right- stuck thermostat. If the temp sensor is on the cold side of the thermostat, it isn't going to read. Grumpy had a post suggesting that a small hole be drilled in the thermostats, I forget all the advantages (note my screen name).

 

My take on the size of the explosion is related to the age of your hoses. New hose=strong, takes a lot of pressure to rupture. More pressure=bigger bang.

 

The entire system is pressurized- the weakiest point will pop, even if it is a soft plug or the radiator itself. Steam will go somehwere.

[Tony D]

I posted this where you posted this before...

I hope you didn't loop your 5/8" heater hose from the head to the return line.

If you did, and you have a thermostat that is stuck, or even slow to open, you allow a dangerously large recirculation line to remain open, so that the waterpump circulates coolant into the head, then out the BACK of the head, right back to the inlet of the pump!

THIS can cause the steam buildup you expenienced, also.

Most people get away with the loop because they kink the line and through dumb luck cut the flow off. But if you are anal (like someon who will remain nameless...), and made a nice loop of free-flowing 5/8" line, you set yourself up for a mobile boiler setup!

Remember, the return from the heater core is supposed to be COOLER than the coolant that came out of the head, so recirculating a large ammount would not be a problem. But letting hot water that came straight from the hottest part of the head to be directly recicrulated to the inlet of the waterpump will cause a shunt of the radiator, and it will just recirculate until you boil it out, or blow the radiator cap.

Plug those hoses with a couple of sparkplugs and see if your heating problem goes away!

I posted this here cause it doesn't look like you came here yet to read the replies, and at ZC.C it looks like you already jumped the thread to check out the suggestions proffered there---and you mentioned your heater hoses being disconnected, so I thought.. hmmmm!

[slownrusty]

Tony - thanks bro! You guessed it, I looped my heater lines, did a nice job too. So THIS is the culprit - yikes!!! I will definately plug those passages with proper plugs. Sheesh, never thought about that when I looped them.

 

Thanks a bunch! I need to take you out for a cold one, surf AND turf!

 

Regards - Yasin

[Z-Gad]

Hmmm...if I am reading this correctly, then if the heater core is bypassed, then you could plug the pipe coming from the rear of the head (#6 cylinder) and plug the pipew on the inlet of the front cover to eliminate a recirculation of the hot water making the cooling system more effective. Is this correct???

[Tony D]

with the heater OFF, you have full capacity in the cooling system.

withthe heater ON, you MAY reduce the capability of the system to reject some heat IF the coolant coming OUT of the heater to the return line is HOTTER than the coolant coming into the inlet from the bottom of the radiator. But it shouldn't make that much difference.

 

You CAN block those passages though, AS LONG AS YOU KEEP A RECIRCULATION LINE IN THE SYSTEM! You need SOME way to recirculate coolant to the inlet of the pump while the enigne is warming up and the thermostat is cold. Otherwise you can cavitate the pump something fierce, and cause all sorts of uneven heating.

A GREAT compromise is to use the thermostatic valve from a late 240Z or 260Z in the bypass line. This valve stays open until it reaches 176 Degrees F, then it closes. This stops the recirculation line altogether to let all the coolant go from the (by now) open thermostat to the radiator.

Notice this is on smog engines where they needed all the cooling they could get. Open bypass when cold, closed when hot.

 

With the L28, there is simply a 3/8" line that bypasses all the time. But the mixture control is temperature compensated, so it really doesn't matter there, eh?

 

Hope this clears it up. My personal preference is to run Water Wetter to make sure there is no spot-boiling back in the rear of the head (which is where they put the head temp sensor on torbo cars...hmmm there's a reason huh!). This is also the reason for placement of the ehater hoses too---you get the absolutely hottest water from the hottest part of the head as quickly as possible for quick heat when starting from cold.

 

You can decrease warmup time by increasing the size of the bypass hose, but must temperature control it to close once up to operating temp so you don't recirc too much and overheat.

Cheers!