RED UFO

I am working on soom problems with my 91 L98. I was reving the engine tonight and noticed the top hose collapsed when I reved it up. I have new hoses and water pump. What would cause this?

leesvet

Top hose???

Odd..thats exit or the return hose...
well, if the t-stat is behind,. only the radiator the other way, I'd say the pump was sucking down the radiator level very quickly creating this heavy suction on the top hose. This would also mean that the system has some good air pockets somewhere...because if it were solid with water, it would'nt have space for a vac..the water would simply move.

See if you can add any to the radiator, see if that makes any difference.

86PACER

Another thing.

Not sure about the top hose but the stock lower hoses come with an internal spring that runs the inside length of the hose for this purpose. This keeps the hose open and prevents it from being able to collapse shut with engine RPM.

When I replaced my factory lower hose the new one (non GM) did not come with this spring. I tried to transfer the spring from the old to the new hose but the hole in the new hose was too small. I would not fit so I had to leave it out. I have not had it collapse on me.

If your old hose has become softened this might be contributing to it. If a new stiff hose still collapses I would call up the GM dealer and ask if the GM top hoses come with this internal spring. If they do this will solve your problem.

Is your lower hose collapsing also?

SQUIRMIN VERMIN 84

you didn't mention if the engine is cold or hot during this test. Is the engine running hotter than before? Is the top hose cool or hot? A stuck t-stat would prevent hot block water from moving into top of radiator and would make a vacuum in top hose and collapse it. Is that a high-volume pump you put in there?

GREGGPENN

Last time I saw someone's C4 doing that, I told them their hoses were getting weak and needed replacing. Less than a week later, the top hose BLEW out!

OEM top hoses have (had) a spring inside to prevent collapse. Most aftermarket's do not. You should transfer the old spring over. Maybe yours has been replaced w/o the spring? I'd get one from salvage (if possible). Better flow if the top hose doesn't collapse.

86PACER

Easier said than done based on my experience when I tried to do it. I cut my old hose to remove the spring to transfer it. But it wasn't going into the new hose no matter what. It just wasn't happening.

mgroshong

Can someone explain why there is an issue with hoses collapsing? Or why there needs to be preventative measures taken? I guess i have never seen that happen on a car.

JackDidley

Thermostat upside down ??

anciano

Waterpump on backwards??

ecorse66

Wrong water pump, (reverse flow)? Serpentine belt routed wrong, spinning pump in reverse?

GREGGPENN

I had to cut my old hose too. But it went right in the new one (from Rock Auto). I can find the brand if anyone cares.

Everyone else, I saw this on an LT4 motor. LT's have reverse cooling.

RED UFO

The new pump is indentical the the one I took off and the belt is routed properly.

ecorse66

It that's the case, leesvet answer makes sense to me.


The only other possibility I can think of is a stuck or reversed thermostat. The upper hose shouldn't collapse unless there is an air lock or a serious restriction. Search for a thread on 'burping' the cooling system. The radiator is lower than the coolant outlet on C4's and it sometimes difficult to get all the air out.


Dave T.

RED UFO

I drained two gallons when I did the water pump. I put 2+ gallons back. How do I get rid of air pockets?

golfkng

Last time I changed hoses on a C4 and added new antifreeze, topped up the rad and then let run with the front end still up on the wheel ramps, then added antifreeze as needed. Also made sure was at the hot level in the overflow. Seemed to burp the rad and no air pockets.

GREGGPENN

Seems like I read where people open the radiator cap JUST after the stat opens -- but before it gets anywhere near 220ish. As the fluid circulates the air can escape. Top it off when it returns to cold.

I never worried about it.

aklim

It was a long time ago but when I did mine, I thought there was a reverse rotation pump for the corvette? I think I had an Edelbrock one for the Firebird but I couldn't use it for the Vette.

They did look similar IIRC.

86PACER

Because the bottom hose is the suction side where the water pump sucks water out of the radiator and pushes it into the motor. The lower hose can collapse in on itself and close off by the suction of the water pump. For this reason GM put a spring inside the lower hoses (not sure if uppper hose to) to keep them open.

So for this reason I say to the OP with the L98. If your lower hose is not collapsing also then most likely your upper hose has simply become soft and flexible.

SQUIRMIN VERMIN 84

totally! Are we getting all of the story? The O.P. says in post #1 he has new hoses...how new, Red?

86PACER

I was under the impression that he bought a new pump and hoses but hasn't installed them since he's "working on soom problems".
Meaning this was one of the problems he was trying to fix and had parts sitting on the bench.

If it's a new upper hose that is collapsing, again I would call GM and ask if their upper hoses come with the internal spring like the lower factory ones do. If they do then one of those will end this problem.

I can't say weather the upper hoses came with springs or not with certainty since mine never had one in it. And I'm the 3rd owner so anything could have been replaced by then. But I know the lower ones did.