69 L68 Water Pump Leak

[Grahame M.]

I finally got the beast running after years in the garage and it sounded nice and smooth for being dormant for so long. Sooo, i went on holidays for a couple of weeks only to return to find a puddle of green coolant on the garage floor.

After doing a pressure test (Cold), which held at 15 PSI for about 10 mins. However, i saw a small buildup (a seep) of coolant on top of the water pump from around the backing plate area. Looking at the pics attached its also coming from the bottom as well.

This pump was purchased, date correct from a US re-conditioner out of the NCRS newsletter.

My questions are:

- Do i pull it out and replace the gasket?
- Do i need to reset the sealing area on the backing plate?
- Is it ok to use Fel-Pro gaskets?
- What sealer is best to use for this area, including the pump to block gaskets?
- Should i put his pump away and purchase a new style GM replacement, Aluminium or cast iron? If you have purchase alternative pumps, supplier and P/N's please.

Also, do the backing plate bolts look too close to the timing chain cover?

Thanks for your help.
Grahame

[Leo G.]

Re: 69 L68 Water Pump Leak

Grahame,
I do not know much about big block Chevrolet engines, however a water pump is a water pump. A similar post (67 bb water pump) at the bottom of the page answered all of your questions I believe. Torque value, sealant,etc. Personally I have used fel pro gaskets with good results, however if you are having the car judged you may want to try and locate a gm replacement. The fastener to timing clearance seems to appear normal. Hope this helps.
Drive em safe

Leo 11875

[Mark E.]

Re: 69 L68 Water Pump Leak

I had the exact same failure by a pump a couple of years ago sourced from a restorer in Arizona who advertises in Driveline.

When I called he said they began using a new sealer which may not be working well. So I pulled the pump and returned it to him for replacement. His replacement pump is leak free so far.

The pump's cover bolts should not contact the timing cover.

[Grahame M.]

Re: 69 L68 Water Pump Leak

Thanks Leo,

I appreciate the response and will read the post you suggested.

Cheers
Grahame

[Grahame M.]

Re: 69 L68 Water Pump Leak

Thanks Mark,

Yeah, it looks like the sealer has failed or maybe the gasket was thin or not used. I'll pull it off the car(again) and check everything. If I'm not mistaken I believe I need to remove the thermostat to pressurise the whole system to check for leaks in the entire cooling system?

If only it was that easy to take it back, very costly from the land of Oz.

Cheers
Grahame

[Mark E.]

Re: 69 L68 Water Pump Leak

If only it was that easy to take it back, very costly from the land of Oz.

Cheers
Grahame

If I'm returning a part for a reason that's the responsibility of the vendor (poor quality, defect, wrong part sent,...) I ask the vendor to pay for shipping to return and replace it. They often will. It's worth asking, especially in a case like this.

Also, once you take it apart in an attempt to repair it, its warranty (it does have a warranty, doesn't it?) is probably void and now you own the problem.

[Grahame M.]

Re: 69 L68 Water Pump Leak

Hi Everyone,

I finally found some time to take the pump off and have attached some photos below.

Looking at the timing case cover the backing plate bolts have definitely been touching and may be part of the reason for the leak, not completely convinced. To fix this is it practical to add additional gasket, pump to block, or replace the backing plate bolts with smaller or flat heads? Car won't be judged.

The leak was definitely coming from the backing plate gasket but it looks like it has a reasonable seal and bolts are tight. Maybe not enough sealer and poor plate (if its the original) sealing area are to blame.

I'm looking for some suggestions on the best way forward, I've also purchased an aluminum water pump as a back up plan.

Can someone also please confirm the timing case cover is correct and not the culprit, and should I take the opportunity to replace the Harmonic Balancer (some suggestions please)? I'm going to hate the answer to this question but should I also take the timing case cover off (if it is the correct one and I don't change the balancer) to check/replace the timing chain? It the original motor but I'm not sure anything like this has been done to this motor. Motor runs smoothly so I don't suspect anything sinister behind the cover but the engine has always seemed down on power for a big block.

Cheers and as always thank you for any help you can provide.

Pump Date Code.jpgTiming Case Cover.jpgPump Backing Plate Leak Area.jpgPump Casting Number.jpgPump Backing Plate.jpg

Grahame

[Mark E.]

Re: 69 L68 Water Pump Leak

I've run into interference between the water pump bolt heads and timing cover on big blocks a couple of times. I solved the problem each time by using a different water pump. My theory is some rebuilders reface the surface that mates to the block and thereby make the pump too short. Again my recommendation is to return the pump...it now has two defects (leaks and doesn't fit properly).

I believe these engines originally had nylon timing gear teeth. So given its age, if you suspect the timing set is original, it may be a good idea to replace it.

The harmonic should be okay if it passes visual inspection.