Leaking Oil Pump; 1969 Eldorado

[Loveofclassics78]

Good evening.

Short story, I replaced the current oil pump on my 69 Eldorado/w 472, which I believed to not be functioning.  I removed the old pump carefully, then cleaned off the mounting area very thoroughly without leaving any nicks or scrapes.  I ensured that both mounting surfaces were clean.  I mounted the new pump with a new gasket and no sealer as I have done before.  This time, I had leaks around the pump.  I pulled it off and redid the process with the old pump, just to see if there was an issue with my new pump.  The old pump actually worked, but it leaked around the mounting area as well.

My question is, is there a general rule not to use any gasket sealer with a new gasket?  I own a 69 and a 72, and I haven't not seen in the shop manual where they say don't use any.  I didn't use any when I replaced the pump on my 72 eldorado/w 500 and it ended up fine. I actually don't see any way around using any sealer this go round as I have repeated the process above several times and had leaks. I even used a new gasket each time.  Is it possible just to use sealer around the sides and bolt holes?

Anybody ever had this issue?  Any suggestions? I appreciate any advice.

Thanks,
Don

[The Tassie Devil(le)]

From what I can recall, there is a gasket, but it is paper-thin .

Bruce.

[The Tassie Devil(le)]

The shop Manual for 1972 says to discard the Pump to Crankcase Gasket when removing the pump, and when installing, replace the gasket.

As these engines are virtually identical to the '69, I think you will find the same instructions in the '69 Shop Manual.

Bruce.

[TJ Hopland]

I believe the gasket is part of the required clearances so I don't think you would want to try without one. 

It seems unlikely but when you were checking the block did you check around the bolt holes?   Maybe someone really over did it and the threads are slightly pulled out making a high spot?

If I was going to try a sealer I think I would try something thin like a loctite 515. 

[Loveofclassics78]

I have used a gasket.  I use a new one each time I replace a caddy pump.  Got extras around here on hand.  For some reason, this particular pump wants to leak.  I thought about some gasgacinch, which is also thin, but strong.  I will have to lookup loctite 515.

[TJ Hopland]

Was the one you took off aluminum?    I assume the new one is iron?   Did you check it with a straight edge?

I had not heard of gasgacinch before but it looks like pretty similar stuff to hitac or the 515 I mentioned.

I have never heard of sealing issues before with these engines so I would be looking for something damaged on the block.  If the one you took off was over torqued its possible that the block has been damaged as well as that pump so that is why neither one wants to seal now.   Like I said earlier it would be difficult to pull the threads out of cast iron but you never know how determined someone may have been in the past to stop a leak.   

[The Tassie Devil(le)]

If it is leaking with a correct gasket, then there is something wrong, either with the pump, ot the surface it bolts to.

Bruce.

[35-709]

Agreed, I have not had any leaking issues when replacing a 472/500 pump --- thin gasket only as I remember.

[Bob Hoffmann CLC#96]

Ask the guys at MTS about "off the shelf pumps"

[Loveofclassics78]

I actually have one of the “blueprinted” pumps from Cadillac high performance aka MTS. I’ve bought one before for my 72. Just can’t imagine I would run into an issue like this, but that’s the nature of this hobby.

So let me ask, the torque for the oil pump bolts are 15ft lbs. If I was to tighten them further, how much more could I go up safely? Would 20 ft lbs be too much?

[The Tassie Devil(le)]

The difference between 15 ft lbs and 20 ft lbs is taken up with the stretching of the bolts.

Or, the damage to the cast iron threads in the block.

The Gasket isn't thick enough to compress much.

5 bolts holding the pump to the engine?   And 5/16" diameter each.   The recommended torque is recommended for a reason. 

Bruce.

["Cadillac Kid" Greg Surfas 15364]

If the surface of the block where the pump mounts is not ABSOLUTELY spotless and the bolts are not tightened evenly in steps and torqued correctly the pump WILL leak. Absolutely no sealant and the thin (0.006") gasket only.
Be sure the leak is not from the relief valve/spring plug.
Greg Surfas

[Loveofclassics78]

Was the one you took off aluminum?    I assume the new one is iron?   Did you check it with a straight edge?

I had not heard of gasgacinch before but it looks like pretty similar stuff to hitac or the 515 I mentioned.

I have never heard of sealing issues before with these engines so I would be looking for something damaged on the block.  If the one you took off was over torqued its possible that the block has been damaged as well as that pump so that is why neither one wants to seal now.   Like I said earlier it would be difficult to pull the threads out of cast iron but you never know how determined someone may have been in the past to stop a leak.   

The one I took off was the original aluminum pump. I’m almost certain the original pump has never been off the car, but you never know.  This is a low mileage car that has sat for a while. It runs good and even though the pumps leak, the oil is moving through the engine. The pump bolts torque good as they should, so I didn’t have any indication that bolt threads were damaged previously.  I cleaned the mounting area thoroughly.  Throwing out ideas, would new bolts help?

[fishnjim]

Just a general technique comment when replacing items that seal pressure;
If it didn't leak before, then it should be able to go back without a leak. 
Bolting is done to apply an even clamping force across a surface of sufficient force.   
Inspect mating surfaces for cracks, pits, unevenness, etc.   Dress as required.
Make sure the bolts & threads are in good condition, if reusing.   Some are non-reusable.   If replacing bolts (recommended) make sure the proper size, grade, and length, "chase" the bolt hole threads, and make sure the bolts go all the way in past the top surface before assembly/torquing.  Oil the threads or use a dab of proper locktite, if torquing.   
Make sure it's the right gasket material and thickness for the application.
Snug up tight by hand, before torquing.  There's a normal torque range by bolt size, don't exceed.  Save the impact wrench for other tasks.
As far as sealants, better to use the thick ones designed to "make a gasket" without gasket, if appropriate, or use gasket adhesive(thin layer) on one side to hold gasket in place, such as permatex, etc.  If you gob on a bunch on both sides of a gasket, it may not compress properly and still leak, then you have an unsightly mess to clean.   Make sure it "cures"(if appropriate) before warming up the engine.   Check the manufacturers literature for the proper application.
Just because the torque wrench reads "spec", doesn't mean the bolt has reached the correct tension.  It just shows it took that much torque to get where it is.   They're correct only if the bolts don't bottom out, cross thread, or have debris in the holes preventing proper tension/tightness/depth.   There are "wet" and "dry" torque specs.   Wet tightens more than dry at same reading, so dry are often higher valued.

The earlier engines, used older generation materials, and weren't as leak tight as today, but you can make them that way with proper sealing techniques.   

[TJ Hopland]

Good thought about chasing the holes and making sure there isn't something like old sealant down at the bottom of the holes that is preventing the bolts from actually clamping down on the pump.    Since the gasket isn't very thick you can't really try fitting it without the gasket to check the bolts but maybe just threading them in and looking at the gap would be the next best option.

[Loveofclassics78]

Appreciate all the advice coming in. I will check the bolt holes, make sure the holes are clear.  I wish that there was a set of new oil pump bolts for sale. I would match up the old bolts to some new grade 8 bolts, just in case the old ones are stretched.  but I’m afraid I wouldn’t find the appropriate lengths.

["Cadillac Kid" Greg Surfas 15364]

Don,
I personally have never heard of the oil pump mounting bolts stretching enough to cause leakage. I will repeat that the mounting surface has to be absolutely hospital clean and the bolts have to be tightened evenly.
Greg Surfas

[Loveofclassics78]

I agree. I’m just considering all options. Only thing I can see that I did different than the shop manual instructions, was I didn’t start at the bolt closest to the regulator.  Perhaps that actually made a difference.  The shop manual also says let the pump mate to the block by turning that screw in. Going to clean the surface off and try the instructions to a t.  Dry gasket first, then if necessary, I’ll pull out some gasket sealant.

[chrisntam]

Make sure it's the oil pump that's leaking, not something else.  Front seal, valve cover gasket.

Use a new gasket and no sealer.  The gasket is very thin.  Make sure both mating surfaces are clean and burr free.

I've only had to do it once, mine sealed the first time.  I too used an MTS pump & gasket.

I didn't read all the responses, sorry if I doubled up on advise...

[chrisntam]

Appreciate all the advice coming in. I will check the bolt holes, make sure the holes are clear.  I wish that there was a set of new oil pump bolts for sale. I would match up the old bolts to some new grade 8 bolts, just in case the old ones are stretched.  but I’m afraid I wouldn’t find the appropriate lengths.

Talk to MTS (now Cadillac High Performance), I got my bolts from them in 2014.  Who's Marty's brother?  He does the Cadillac stuff now.