Current Water pump Sealant Options

[t36]

Searched for a bit, and found a lot of answers but products have changed names and formulas since those old posts.

I know the WP can be installed with a dry gasket but I’m going to install with a bit of sealant as the previous gasket had sealant and it did not leak.

Hylomar Universal Blue is the most common recommendation. It’s difficult to find in North America and expensive if you can.

Permatex Permashield 85420 this is Permatex’s version of universal blue. The specs appear identical and the package says “comparable to Hylomar Universal Blue”.

Curil T2 previously, Curil K2 was a popular recommendation. T2 specs look similar to the Permatex option, and actually appear to outperform it in temperature range. It also is not solvent based so there is no flash time required.

Or

A standard silicone rtv type product

The specs of each appear to be fuel resistant and non hardening. Specs are one thing, but what are you guys using and enjoying?

I enjoy wrenching, but I don’t enjoy redoing things so all of your experience with the above is very valuable!

[AudiSport]

I've been using Loctite gasket adhesive on rubber and paper on 2 Audis so far. I think I used it on the cam tower gasket and also the intake gaskets....

https://www.fcpeuro.com/products/gasket ... ite-234910

[walfreyydo]

I thought the water pump comes with a gasket and should not need any additional sealant.

Personally, thats what I would do, making sure the surface for the gasket is completely clean with no residue or corrosion build up. Plastic scraper or roloc(sp?) wheel work well for these situations, or very careful usage of a razor blade.

Sometimes adding sealant where its not needed can actually cause bigger issues, especially if over applied, such as pieces of the sealant breaking off and getting into the system and clogging ports and so forth, or actually being an impediment to getting a good seal (cam tower gasket for instance).

Heres a good guide in case its needed
https://www.pelicanparts.com/techarticl ... 4tt62HY-RC

[951tom]

I had problems with leaks when I replaced my water pump. The block surface looked immaculate after cleaning & the pump was new (not rebuilt) so never figured out what my issue was. Upon reassembly, I smeared a thin layer of Permatex water pump & thermostat housing sealant on both sides of the gasket. Problem solved.

Tom
'87 951

[Tom]

Knock on wood -- I've never used sealant and never had a leak, so I imagine any of the water pump sealants would be belt and suspenders. I just wouldn't use RTV on it myself.

[t36]

Knock on wood -- I've never used sealant and never had a leak, so I imagine any of the water pump sealants would be belt and suspenders. I just wouldn't use RTV on it myself.

About a year ago I put a tiny bit on both sides of my oil cooler/filter housing. No leaks, so I did a similar application on my water pump. Sure makes positioning the gasket easy. I’ll report back if it leaks.
I went with Curil T2.

[whalenlg]

One other note - i used an oil stone on the block surface to make sure I had a level surface.

[dr bob]

I've been watching this thread for a few days, and after some deeper thought...

My decision to use a sealant is almost completely dependent on the quality of the surfaces. Specifically on the engine side, scrapes, gouges and grooves seem to happen when an old gasket needs to be scraped off, maybe because a fabulous sealant was added at a prior pump change. For my own cars that haven't enjoyed prior care from others, there's no sealant needed since tools never touched the block' gasket flange. For others with even just some small scratches, the requirements change. Definitely follow @whalenlg's guidance to test and smooth any scratches with protruding material. A small oil- or ATF-wetted oilstone is excellent, with a reminder that you just want to remove the part of the scratch that's proud of the main surface level. Any more, like trying to polish the whole area, risks more leakage.

For water pumps especially, using a progressive torque-limited tightening pattern is essential to getting a nice even squeeze on the gasket material. Sort of the same guidance shared for oil sump gaskets, where an uneven squeeze risks leaks. If you aren't already a religious torque wrench user, at least use one for water pump bolts.

I've gotten into the habit of 'chasing' the threads in pump bolt holes in the block. Use a real thread chaser for this, rather than a plug or bottoming tap, and some brake-clean to flush. A thread chaser looks a lot like a regular bolt with a slot cut along the threaded length; carefully run in and out to remove any remaining crud, old sealant, etc., then flush and let dry completely before fitting the new bolts and washers.

I'm in the 'always new bolts' club for water pump bolts. While some preach about using stainless for these bolts, I still use plated steel bolts, and add a VERY THIN film of Teflon thread sealant to them starting one or two turns from the tip of the bolt. Keeps the sealant from the bottom of the hole, and supports removal with the thread chaser next time. On the 928 anyway, a couple of the pump bolts go into oil or coolant galleys. Plus the thin coating virtually guarantees that the bolts will come out effortlessly the next time you want to remove them, as it reduces possible galvanic 'welding' and corrosion in the aluminum block.

If I do decide to use a gasket sealer, it's a very thin film of Hylomar, and usually to hold the gasket to the pump only. The block side stays dry unless there's damage. You can buy Hylomar in small tubes in card packs at most plain old local auto parts stores (POLAPS), with a Permatex brand. Hylomar doesn't dry out in service, and is removable with brake cleaner and a paper towel after disassembly. I can't overemphasize the "very thin film" application. Squeeze-out generally means too much, plus it looks a bit tacky to have blue stuff showing after the job is done. Remember that we use it only to fill scratches and tool marks in the metal; the gasket itself works amazingly well dry when properly and evenly squeezed between parallel metal faces.


So far, this strategy has prevented leaks on more than a few places on cars that have passed through the workbay. Whether you choose to use Hylomar, Honda-/Yama-/etc. bond products, or non-hardening regular Permatex sealants, the thin-film guidance still applies. Just enough, and no more please. And Not Silicone please, regardless of how tempting it might be.

Several plus one or two decades ago, I bought a spiffy Tokiko torque-limiting "driver" that's scaled in lbs/inches as well as NM. Like a fat screwdriver with a vernier scale for the torque setting. Critically it has a 1/4" drive extension included, and has been my go-to for things like the water pumps, plus any other covers and duties that include 6mm or smaller threaded fasteners. 5-6lbs/ft is common spec for the 6mm bolts used on the water pump, and I sometimes reduce the spec by 5-10% when the threads are lubricated but spec'd dry. These values are smaller than you might want to guess at with a regular ratchet driver. Overtightening into an aluminum block risks pulling slightly on the threads, maybe distorting the sealing face around the hole. Absent the lubrication on the thread, there's also the risk of plain old wear and maybe galling on the thread in the block, something that doesn't seem like a big risk. But it's so easy to avoid, why not just do it like you mean it? Incidentally, the oilstone trick is pretty darn good at identifying damage and distortion of the sealing face around the threaded holes. A few gentle strokes with the stone will highlight that distortion, and help drive your decision on whether or not a sealant is a good idea on the gasket.

Hope this helps someone.

[t36]

Dr Bob, excellent excellent info there! Great things to be mindful of.

I approach anything that has multiple fasteners like tuning a drum.
And I used brand new bolts/nuts on my new pump. Plus, a very thin smear of non-hardening non silicone sealant (Curil T2).

After lots of googling I came to a conclusion among mechanic friends that the new Curil T2 and the Permatex "Hylomar" equivalent are essentially going to be the same. The one drawback of the Hylomar is that its solvent based - so if you apply the gasket too quickly: the acetone will not have had a chance to evaporate. The T2 however, has an often redacted SDS. And I 100% agree, you nailed it, thin is better! Just filling scratches.

I have a nice little 1/4" torque wrench with an inch pound scale. I honestly use it on all small fasteners. The small ones break the easiest - so I don't really use "hand tight" on those ever.
I brought my water pump fasteners up to their final torque spec at 4 or 5 torque intervals. Part of the fun of these cars is the wrenching, so I enjoy adjusting the torque wrench a couple times!

[cda951]

I use a very thin coat of Curil T on every paper or fiber gasket that I install, have done so for 20+ years. Not so much for the sealing capability (it helps a small amount, clean and even surfaces are the primary factor), more so since like Hylomar, the Curil T's tackiness makes it stick to the part upon installation, and the non-setting properties makes the gasket much easier to remove in the future. That is a concern for someone who does this for a living .