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TxBuicks

Water Leak at Rear of Engine - 1991 Roadmaster

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My 1991 Roadmaster Wagon has sprung a leak! A big one. The odd thing is that the water appears to be coming from the top rear of the engine, up against the firewall. It is the 305 ci (5.0 L) V8, not the 350 used in 1992 and 1993, nor the LT1 used in 1994-1996. I can't even see where it is leaking. I have a bad feeling about this. I can fill it up but it starts to overheat within 10 minutes, hissing and steaming from somewhere by the firewall. There is no water in the oil, which rules out a head gasket, and I can see the heater hoses and they look all right. Any ideas where this water could be coming from?

PS: Please don't say freeze plug, because I'd have to pull the engine to fix it.

Edited by TxBuicks (see edit history)

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Could still be the head gasket even if no water in the oil. The leak can be from the water jacket to an external area rather than to the cylinder.

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With the engine cold pressurize the cooling system to about 20 PSI and crawl back there. You should see it. Stant makes an adapter for the reservoir tank.

Bernie

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The Chevy V-8s of that vintage usually did not have head gasket problems, unless somebody didn't keep the coolant changed often enough.

FIRST thing I'd do is to get a 12-point wrench and check the intake manifold bolts -- ALL of them, in normal torque sequence (for good measure). As little as 1/4 turn loose can make a seep happen, especially at one of the end-area bolts. IF there are any quick-disconnects on the heater hoses, they have been known to crack/fissure, which can also cause a coolant leak--there are "steel" ones and "pot metal" ones. As with any quick-disconnect, there are also rubber seals in there (which you end up replacing when you change the quick-disconnect fitting).

There can also be some plastic ends on the heater core pipes, which can have "age-related" issues.

IF it's a head gasket problem, I'll buy your personal lunch at Bodacious in June! (With acceptable proof of such failure)

NTX5467

Edited by NTX5467 (see edit history)

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It WAS a heater hose after all. I did not realize until I got the manual out that there is a heater hose going from the back of the intake manifold to the heater control valve. That 12" hose was the original hose, had a date stamp on it of 02/15/91. It was soft enough for the hose clamp to eat through it. Although it was tough for my huge hands to get to, it was easier than what it could have been. It's back on the road again. Thanks for the suggestions, though.

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