I'd appreciate some advice on a coolant leak my '65 Riviera just developed. My car has its born-with 425 dual-quad engine. It was rebuilt about 12 years ago. I drive the car regularly, but only put maybe 1,500 miles on it per year. I've owned this Gran Sport since 1983, so we have a long history together. Last week I noticed coolant dripping down from the front of the engine from around the water pump area. I assumed the water pump had failed. Over the weekend I sourced a brand new water pump from NAPA and set to install it last night. All went well until I got the old pump off and upon examining it further noticed nothing seemingly wrong with it. There was no coolant coming from the weep hole and the bearings had only very minor play. While comparing photos I took of the leaking area before removing the water pump, I realized the leak was probably coming from the top passenger side of the timing cover. The coolant pools along a 'valley' formed by the webbing in this area of the timing cover, then drips down onto the water pump, as shown in this photo: This second photo was taken last night, after I removed the water pump: I'm guessing the coolant is escaping from the gasketed area between the engine block and the timing chain cover. So, to my questions: Is it common for the timing cover gasket to fail, at this location? Or, is the leak due to something else wrong with the timing cover? Looking at the front of the timing cover, it seems to be in pretty good shape, clean with no corrosion damage evident. But, maybe that's not the case where it meets the block. Is the leak coming from the gasket, or from the bolt. The bolt was not loose when I checked it. What should I do to fix this? Do I need to remove the timing cover? How involved is this to do? If it's the gasket that has failed, can I shove something in there to stop the leak? Or would it be worth putting in some coolant tablets or "Bars Leak" to try to plug the gap? Thanks for sharing your knowledge, and advice.
Gsgtx got me now thinking the leak may have come from the heater hose... Hmmm. Okay, here's two pics of the water pump I took off the engine last night. There is a fair bit of 'crud' on the heater hose connection. You'll see the coolant has dribbled down from this area over the pump: Would this be consistent with the heater hose leaking? Or, could it still be caused by coolant escaping from between the timing cover and the block above this area of the water pump? Here's the backside:
Yes, still think it is that hose and tube where the leak was, as the evidence of leaking on the front side, corresponds with the puddle behind that bolt boss. Clean that corrosion off with a wire wheel/brush. (I use bronze brush, they are less aggressive to healthy metal). Then get the "slow set" JB weld (it is stronger), use it to fill and contour the hose tube, then a flat file to shape, and sandpaper to smooth. Make sure you have the "ridge" to help retain the hose. You can also put the cover on without gasket and torque the bolts and use feeler gauges to see if the surfaces are mating well. To gasket, use I use black 3M weatherstrip adhesive to hold to pump, and Permatex "Right Stuff" on the engine side. Then I install bolts finger tight to the point the gasket sealant just starts to squeeze out, let it set for an hour, then torque to spec. Let it sit for 24 hours before filling coolant. Make sure the hoses are in top condition, and those "single wire spring clamps" are the best for fully applying even pressure around the hose. Then next best are the Fuel Injection clamps.
I would agree it's the heater hose. First off, those spring clamps weren't the best. Next, that wall of corroded crud is a guaranteed leak, the aluminum underneath is probably full of holes. There's no "landing" area for the clamp to pinch off; the fact that it's essentially floating on swollen crud means it's been compromised there. The water pattern rolling down the pump lines up directly; -just coincidental that there are two bolts there. That's where your engine vented off pressure; at first just an invisible mist, and as the crap built up, then came the actual liquid leak. You could reuse that pump, but since you have it out already, it might just be better to replace it. Old pumps don't like to be disturbed and reused, they have an alarming tendency to fail or leak immediately after re-instalation, - that's been my experience, I'm sure others have had better luck. GM built those water pumps to be used for a period and then tossed, they were a sealed non-serviceable replacement product, and unless you have the tooling to replace the seals, bearings and the packing, along with re-machining the shaft, it's usually not worth the risk to re-install a used pump. The water pump is the Nailhead's "Achilles' Heel", or a known failure point. That hose clamp may be factory, but it's crap. There's a reason why most people tossed those things back in the 70s.
I was thinking heater hose too. You just have to clean it all up and carefully watch where the leak starts. Maybe sprinkling surfaces with baby powder will help ID where it's coming from.... dunno if I read that online or thought of it myself? A more common leak point is where the cast iron water manifold fits into the alum timing cover. The alum often corrodes, requiring a JB Weld repair, a new o-ring, and some sealant. Here's a JB Weld tip..... apply it, and cover it with masking tape. That will allow you to smooth or form the repair (and prevent sagging of the JB). When the JB weld cures, just peel the masking tape off.
when you tighten the clamp make sure it is not in between the lower part of the hose and the upper ridge. i always get the clamp as low as i can, not sure if that's right or it should be on the top ridge ? but after sanding and j b weld like the guys say, it stopped leaking.
I had the very same symptoms on my 425. It was leaking at the o-ring on the bottom of the thermostat housing where it goes into the timing cover. Mine was badly corroded and had to replace the timing cover.
Thanks Michael, Marc, and others who piped in! You've convinced me to ditch my old water pump and put in the new one I have on my shelf. Plus the new one is a 5-vane pump vs. the 3-vane that was in before. That should help with engine cooling on the few super hot days we get here in the Northwest. I'll update you all once I get the new pump installed. Wish me luck!
Update - Last night I finished installing the new water pump. I used a torque wrench to ensure all bolts are tightened to spec. Getting the pulley, hub, and fan on to the water pump hub was fun. First time I put the pulley on backwards (it was getting late) . Putting it on right took rather less time. While I was at it I cleaned up the valve covers, gas deposits from dual carbs, degreased all around and ensured all wires and electrical connections were good. By now it was almost midnight, so I went to bed. This morning I refilled with a 50/50 mix of water and undiluted antifreeze. Car started right up. Went to examine water pump.... To my chagrin I saw the small puddle forming again atop the timing cover - Drat! Then got the idea to try some radiator stop-leak, what the hell, nothing to lose, right? So I drained the coolant and dissolved a canister of powdered AlumaSeal stop leak (from a small tube of brown metallic flakes) into the recovered coolant and re-filled the radiator with the new mixture. I took the car for a drive to fully warm up the engine to circulate the coolant with the leak stop. After about 15 minutes drive there was NO LEAK! I'm pleased the leak appears to have been plugged, at least for now. I'm under no illusion that the timing cover won't leak again, but hope to get a few miles out of the car before having to tear into the engine again. Had I known my initial suspicion about the leak coming from the timing cover above the water pump was correct, I could have put some JB Weld along the flange between the water pump and timing cover at the leak location. Is this what I should do if the leak comes back? Or should I dump another tube of stop-leak powder into the radiator? I know the answer is probably a new timing chain cover, but in the meantime just wondering what you would do, if you were in this situation. At least I know I have a good water pump now! -Alex
AND, when you finally get a new timing case cover it will probably leak as ALL the ones being made at the moment are porous.
Good to know; I was thinking of buying one. Now, not to hijack this thread, but do you know if the timing covers for the Big Block Buick are porous as well?
You mean the 400-430-455's???? They have been around for a LONG time so any deference's have been worked out. The "Nail" covers originally which I had helped to design were an excellent piece. Then the molds got sold & a lesser expensive casting manufacturer was selected. So this is where we are today. The provider I'm sure will be taking a loss on the ones in stock, unless they come up with a way to test them BEFORE they go out to the public for resale. OR until they get the problem straightened out. We'll have to see what transpires.
Hi Tom - thank you for the heads-up about the repro timing covers! Does this mean there is no real fix at the moment for a leaking timing cover? So far the Stop-Leak fix seems to be holding on my motor. But, if the leak returns, what would you do?
Alex, 1st. thing I would do is to find EXACTLY where the leak is originating from. I've done this in the past with, so far, good results. I let the engine heat up to the point of just overheating to try & get the aluminum as expanded as possible. Then I immediately drain the coolant, clean the area with Brakleen & coat the area with JB Weld. As the aluminum cools & shrinks the JB Weld will be in the pores of the aluminum & when it drys should be just about be an integral part of the timing case cover. BUT we must 1st. positively identify the location/ source of the leak. If it's coming from the O-Ring area in the water crossover manifold that will be another different repair. Tom T.
Hi Tom, Thanks for the tip about using JB Weld to plug leaks in the timing cover. How do I "let the engine heat up to the point of just overheating it? Would I remove the belt driving the fan to accomplish this? Would it overheat this way if I just left the engine idling? Or would I need to take the car out on the road? As these cars only have an 'idiot' light to indicate overheating, I'd use a IR Temperature gun to read the temperature at the engine water neck. But, at what temperature should I shut the motor down? The leak in my timing cover appears to be coming from the gasketed surface between the engine block and the timing cover. See first two photos in my first post above. Would I just smear JB Weld into this area. overlapping the gasketed area, in hopes it would seal the leak? Thanks for sharing your experience with me.
If that is where the actual leak is, the proper repair would be to remove the timing cover and replace the gasket. If you then find corroded aluminum, the damage can likely be repaired with JB weld.
