SL65MONSTA

My cars been driving fine up until recently the top radiator hose comes off anytime I put my foot down, seems as if there is too much pressure in the cooling system ( I may be completely wrong) and that is the weakest point in the system to give, the hose has previously blown I could not source a hose or find one in Australia , So i put a temporary pipe with two clamps to fix it which I dont think should be the issue here, but Im no expert maybe it affects it somehow.

Although there are a few strange things which should give someone on here an idea of what it might be, I just cant figure it out! here is what happens before the top hose comes off. When I put my foot down, intermittently the power steer feels as if its lost "power" (hardens up) maybe for a second or two if that, and I hear like a belt noise also happens at the exact same time for a couple seconds, then I look in the rear view mirror and see a mist of water hitting all the cars behind me, which means the top hose has just come off , all these things happen at the same time. Someone should know what is happening.

What I thought was is the water pump seized up , however the water pump was not replaced long ago ,maybe 5000-8000kms ago, I have also completely removed the thermostat previously not sure if this is maybe to blame. The fan runs perfectly fine and is not overheating at all (until the dam hose comes off).

I have taken out the fan, removed the serpentine belt and all pulleys have no play or seem seized at all. My other thoughts on this are the AC compressor clutch is "intermittently" seizing , or the water pump ??? it could also be the tensioner but none of the pulleys seem to be hard or have any play on them.

How does one resolve such a complicated matter?

When I drive before the top hose comes off , you hear the belt grab (screeching noise) for a few seconds, I then lose power steering for a couple of seconds (pulley or belt disengaging) and then it seems as if the water pump is also disengaged too , hence it blows of the top hose. Or maybe I am blowing of the top hose and the coolant is then spilling onto the rubber pulley making the noise.

Does the thermostat control the pressure or regulate it in anyway, also does the water pump or could it intermittently seize ? the ABC pump seems to be hard to turn but I'm thinking this is normal as I also took of the serpentine belt of my S600 to check and the pulley resistance is very similar.

I am hoping to god it is not head problems or head gaskets.

is there a way to figure this out without pulling of the heads etc?

Rommies

I am no expert on this but it sounds to me like a tensioner issue. The fact that you hear the belt slipping (when accelerating) tells me this. What is the condition of your drive belt? (v-belts)


Also the hose pipe that you replaced, can it handle the high heat water temperature & pressure? Is it the same diameter as the OEM one?

Please also take a video & maybe some pictures

SL65MONSTA

Replaced pipe is maybe about 3inches long and very close to the original hose pipe diameter. The screeching noise happens at high acceleration only for a second or two then I lose power steer at the exact same time and the top hose releases, or the top hose releases and then the water causes the screeching not sure and probably impossible to tell which way it's happening. I might just replace the radiator cap and the tensioner and see if that changes anything. I just don't wanna have so much downtime on these cars!

next2pool

Is it possible you have a bad engine mount allowing the engine to move and pull the hose off? The power steering squeal may be a reuslt of coolant on the belts.

SL65MONSTA

issue turned out to be wrong radiator cap, got my s600 mixed up with my sl65 one thanks much guys though

SL65MONSTA

turned out to be the thermostat sensor is different on the S600 to the SL , which was sending the wrong numbers for the shroud fan to turn on, in effect causing pressure build up to burst and leak.

FxFormat

I'm having this same issue but it's not the hose popping off, it boils out of the radiator expansion tank cap. I've tried 2 other caps, one i bought on ebay that supposed to be for this car but it didn't work, i thought the cap was bad so i bought one from Advance and it seems to seal tighter but still coolant spills out of that when i get on it. Car doesn't overheat, but coolant is lost through the cap and would throw a low coolant light. Any ideas?

Rudeney

Are you sure it's coming from the cap and not the reservoir itself? There is a seal between the two sections (black top and translucent bottom) of the reservoir and over time it will fail. You have to replace the reservoir. It; snot too bad - under $100 IIRC.

FxFormat

Rudeney

The cap is rated for a given pressure. If it exceeds that, it will release pressure. Maybe you have another issue that is causing excessive pressure.

FxFormat

Rudeney

I assume the coolant level is correct? It should be at the top of the translucent section of the reservoir when cold. Also, I'd still inspect the reservoir carefully to make sure it's not cracked - that is not an uncommon problem on all MBZs (they almost all use the same reservoir).

FxFormat

Rodney, i think you might be right, today i did a test, i draped the mouth of the reservoir with a towel and drove around until it got home. Then popped the hood and noticed the towel was dry, then inspected the area where white meets black, seems to be seeping. I'm going to order a new tank from online and see how it'll do. Thanks again, can't believe this tank on ebay cost more used, than buying from the OEM website u linked me.