Zerex G05 Coolant

[Joseph S.]

In the past few months I have had the water pump backing plate, on at least three occasions develop coolant leaks on my '66 L36. I would have assumed it was a poor quality rebuilt (done by me) but the third leak was a different pump, rebuilt by a professional rebuilder. On initial rebuild the backing plate gasket was installed dry (as I have done in the past with no issues) and subsequent rebuilds were done with a blue RTV and grey RTV from a GM dealer (in combination with the paper gasket).

I use Zerex G05 coolant in this car. First car I have done so, upon reading recommendations from others on the forum. Now I have heard (unsubstantiated), that G05 coolant 'may' undermine some paper gasket material.

There is only so much torque you can achieve with the slotted screw head backing plate retainers.


Before I try this again, has anyone heard anything about G05 not being compatible with certain gasket material?

Joe

[Leif A.]

Re: Zerex G05 Coolant

In the past few months I have had the water pump backing plate, on at least three occasions develop coolant leaks on my '66 L36. I would have assumed it was a poor quality rebuilt (done by me) but the third leak was a different pump, rebuilt by a professional rebuilder. On initial rebuild the backing plate gasket was installed dry (as I have done in the past with no issues) and subsequent rebuilds were done with a blue RTV and grey RTV from a GM dealer (in combination with the paper gasket).

I use Zerex G05 coolant in this car. First car I have done so, upon reading recommendations from others on the forum. Now I have heard (unsubstantiated), that G05 coolant 'may' undermine some paper gasket material.

There is only so much torque you can achieve with the slotted screw head backing plate retainers.


Before I try this again, has anyone heard anything about G05 not being compatible with certain gasket material?

Joe

Joe,
Nothing negative whatsoever. All I ever used was a 50/50 mix of Zerex G05 and distilled water. Again, no adverse effects. I, think something else is in play here.

[Joe L.]

Re: Zerex G05 Coolant

[QUOTE



Before I try this again, has anyone heard anything about G05 not being compatible with certain gasket material?

Joe[/QUOTE]

Joe-------


I've never heard of any such problem and never had such a problem using it.

[Duke W.]

Re: Zerex G05 Coolant

I've not heard of any issues with G-05 and paper gaskets, but it's very important to make sure the mounting surface for the back plate is level along with the sheet metal cover.

Many of these pumps have been rebuilt multiple times over the years and surfaces can get warped. The back plate can be a particular problem because, like oil pan bolts, multiple bolt tightenings, especially if overtorqued can upset the material around the hole.

What i do is lay a good straight edge across the line of bolts and use a very thin feeler gage to check for level. You can usually even see how the material is upset around the bolt holes. Then use a flat face body hammer to tap them down so all are level with the rail.

I don't think there is a torque spec for those cover bolts in the service manuals, so get a chart off the internet that lists a "standard torque" for the bolt diameter, thread pitch, and SAE grade. I doubt if it's much more than 10 lb-ft for those cover bolts.

Duke

[Joseph S.]

Re: Zerex G05 Coolant

Thank you guys for the input- I'll most definitely rule out G05.

Next maybe check the pressure cap-

Joe

[Gary B.]

Re: Zerex G05 Coolant

Thank you guys for the input- I'll most definitely rule out G05.

Next maybe check the pressure cap-

Joe

Joe,

Are you saying you think the pressure cap is out of spec and allowing the cooling stystem to over-pressurize? Which is then leading to the leak at the water pump backing plate?

Gary

[Joseph S.]

[Jim D.]

Re: Zerex G05 Coolant

My thought is that could be a possibility.
After two different water pumps and 3 reworks, two different RTV sealants - I want to be sure I don’t miss anything when I put it back together
Your thoughts?
Joe

Don't use a RTV sealer where anti-freeze is concerned. I've used Permatex 2 or Permatex anaerobic without issues for 50 years. Especially important for C-1 front engine mounts.

[Joseph S.]

Re: Zerex G05 Coolant

Thanks Jim
I've used Permatex anaerobic on my transmissions for some time with good results. I'll be a little more thorough checking for warpage and insuring the plate securement screws are sealed along with trying Permatex.
Joe

[Mark E.]

Re: Zerex G05 Coolant

Hi Joe,

You can save time by pressure testing after the cooling system is put together but before other stuff is assembled (pulleys, fan, belts, etc.).

Testers are inexpensive and locate leaks in a snap.

BTW, your car was my favorite at Frisco.

[Joseph S.]

Re: Zerex G05 Coolant

Hi Mark,
I've been using the same tester for 40 years - never even started the car after the last rework. Backing plate leaked on the pressure test.

[Gary B.]

Re: Zerex G05 Coolant

Joe,

Just curious. Do you know the pressure value when it started to leak?

Gary

[Joseph S.]

Re: Zerex G05 Coolant

Honestly no. It is possible I applied too much pressure on a cold system. I think the system s designed for a 15psi.

[Mark M.]

Re: Zerex G05 Coolant

About 10 years ago I had a 67 427 car water pump back plate leak with a number of different sealers tried. I used permatex right stuff, let it set over night and it leaked no more.

[Joseph S.]

Re: Zerex G05 Coolant

thanks Mark
Joe