To RTV or not.....? Here we go...

[RustyWa]

I know I'm opening up this can of worms, but.....

Has the opinion changed on using the hi-temp (red) RTV on the pushrod o-rings? Yes or No? I think through all the threads I've searched it was pretty much 50/50.

Also, if you do use it, is it the practice that you use just a little on both ends of the tube?

Thanks.

[Bleyseng]

No, don't use rtv on the o rings. Use the viton seals, clean the pushrod tube spotless, and clean the block and heads. The o rings float allowing the tubes to expand and move as the engine expands. If everything is clean and you install the tubes without pinching the o rings you will have a good leak free seal.
Geoff

[JP Noonan]

I agree. Use a scotch brite pad to clean inside the heads and use oil on the o-rings to make installation easier.

[J P Stein]

'O' rings are meant to "Float". I use silicone grease on all of em'.

[MASSIVE TYPE IV]

Over time I have tried it about every way I can think of. Seems like the worst leaks were when i only used oil or grease and no sealants. VW designed them to work like a conventional o ring, but at the head end the made the tubes sit into a trough that leads to leaks more times than not.

I use loctite 518 "Gasket eliminator" on my pushrod tube seals. We have engines with over 100K on them without a leak, and one that rusted a hole in the tube from being too dry.

The viton seals are OK, but if the conventional seals are used, with the 518 and a "Chill" method things work better for us. I normally freeze the tubes for an hour or so with the o rings on them,use the 518 and slip them right into place with no worries...I just did a 2056 thats as dry as a bone after 23 full 6,000 RPM dyno pulls.

[norustscott]

This brings up two related questions.

1. I have several sets of seals. Green ones , Black ones and red ones,..Is one color indicative of a manufacturer?

2. Just how much does a type four engine expand once @ operating temperature? Has to be measured in hundreds of an inch...a quality gasket sealer, RTV stuff can take the expansion...

Completing the long block this week. I will go the loctite method.

[MASSIVE TYPE IV]

Expansionhas alot to do with how hot the engine gets, it is very inconsistant.

Make sure to get Loctite 518, it is not the same as regular loctite, and be prepared to pay 18 buckes per tube for it. This stuff is good, especially on oil pumps and case halves. It is anerobic, the samecomposition that Porsche recommends for 911 case halves.

[Va914]

Jake, what about the stuff (Need to watch it again fo rthe name) you used in the Bug-me-video? Is that a replacment to what you guys are talking about here?
Or are they used in different places? It seems the stuff in the video was used everywhere!

Thanks
Kerry

[MASSIVE TYPE IV]

The stuff we used in the video is god too, but is easier to use than 518, especially for a novice, like the video was aimed at..

The 518 is fast stuff, if it goes without air for 2 seconds is is set permanantly. Don't use it on cylinders, they will never come back off again!

[norustscott]

Jake, Is that the whole product number...Loctite 518...I don't see it on the Loctite Web site...?

http://www.loctite.com/catalog/product.html?ProductLine=518

[sammyg2]

Thermal expansion rate of steel is about .000006" per inch per degree (F) rise over ambient. Expansion rate of cast iron is very close to that, just slightly less IIRC. So we can measure the distance, calcumalate (word stolen from JP) the temperature rise, and determine the total expansion.
Here's where it gets sticky:
you have to calcumalate the temperature rise of the pushrod tubes and compare that to the rise of the cylinders. That will be the true change in position of the o rings, which were designed to float in the bore as the pushrod tubes expand and contract compared to the cylinders.
I have installed the o rings with and without glue, and both methods worked (limited amout of miles on each test, sold the car).
If the o rings are correct, and the seating bore is smooth, clean, and not oversized, the o rings should work as designed and seal correctly.

That is also assuming that the pushrod tube is in good condition where the o rings seat. i suspect that this is where most leakage comes from, and where sealant would help the most.

[dman]

My 2 cents,

When I rebuilt my engine I was also conserned with this seal. I cleaned my case and perchased new tubes fromm PP. When I recieved them I measured the diameter of the seat where the seal goes and none of them were the same or close to being round. If I remember correctly there is also a seam that runs the length of them. I ended up turning both ends in a lathe to clean them up an make them all the same. After checking the fit I installed them with hi-temp grease. No leaks