coolant flange still leaks!!

[92EcoDiesel Jetta]

I replaced the flange betweeh glow plugs 3&4 last week and I just noticed a little coolant collected in the block crevices below it. The bottom flange bolt din's feel right when I tightened it, felt partially stripped. A helicoil kit is $50 and I don't feel like spending that kind of money. I am thinking of cleaning out the threads real well with solvent, pack just the threads (not the entire hole with JB weld leaving the first couple of threads free of epoxy so I can get a tap started and rethread it after it's cured. Since it's an o-ring seal, the torque on the 2 flange bolts do not have to be that great. What do you think? Will it work? I have a set of metric taps but no helicoil kit.

[92EcoDiesel Jetta]

Perhaps you're right Andrew. I still think epoxy will work since it's good to 500F and the 6 mm flange bolt won't need more than 10 ft lb of torque. But the repair stud sounds appealing since I have a tap for it, that's what I'll do.

[macka]

In my experience JB weld fails within a month for this application. You are better off retapping to a larger bolt size, and if you can't retap, you need to get the gab filled with weld, and redrilled and tapped to spec.

[92EcoDiesel Jetta]

Ok, point taken. Who sells repair studs?

[92EcoDiesel Jetta]

I called NAPA and also the Nutty Company, neither has the "repair studs". Then I called Ace hardware- a woman ansewered and I was thinking to myself she's not gonna know what I'm talking about. But after 2 trips to the isle she came back and says "yeah we have it 6 x 1 one end and 8 x 1.25 the other $2.35 ea.".  She says the box they're in are marked "Automotive studs",  hehehe.

[92EcoDiesel Jetta]

Sounds like you're in business.

I wouldn't say that yet. I am sure there will be more surprises I took a closer look at what's involved and to be able to drill the bottom hole (for a 8 x 1/25 tap) straight on I have to remove the turbo oil line that's coming off the top of the oil cooler and that fitting is very rusty! I've got it soaking in penetrating oil now. Still have to find my 17 mm crowfoot for the nut on the turbo end.

While I was pokong around I lifted the upper hose a bit on the flange and coolant poured out so that bottom bolt hole is definetly not holding tight.

[92EcoDiesel Jetta]

If you have the full metric tap set, maybe you can avoid drilling by tapping to 7 x 1.25 and then tapping again to 8 x 1.25

I do have a full metric tap set. Can you do that without using a tap drill and not break the tap? I know to go easy and not force it in and all that and go in 1 turn back out 1/4 turn etc.

[92EcoDiesel Jetta]

It might not be the "right" way to do it, but I've done it more than once that way without problems.

Thanks for that idea. I'm going with it!

[92EcoDiesel Jetta]

Well, I spent the last few hours pulling it apart and now it's back together. What I found was not a stripped bottom bolt hole but a cruddy one, which I cleaned up with a tap. What was causing it to leak was pitting of the aluminum right where the o-ring make contact with the head. I did scrape it clean previously but I failed to run my finger over the surface to check how smooth it is. Anyway some of the pits were 1/16" deep 1/4" wide. I scraped it down to bare metal and cleaned with alcohol then filled with epoxy and wet sanded it between coats till it's level, then put it back together with a light film of RTV. I am waiting for it to cure overnight before filling it with coolant and test for leaks. I used a generous amount of anti-seize on the 2 flange bolts and will do the final tightening tomorrow. Hope it works. What causes pitting anyway? Wrong coolant or cheap aluminum?

[92EcoDiesel Jetta]

Did the final flange bolts tightening, put the hoses back and filled it. So far no leaks.  What type of coolant is best for this engine?

While I had the flange off, I took out the coolant temp sender, hooked it to an ohmmeter and put into a pot of water on the stove with a thermometer, turned stove on medium to slowly heat up and made a table of resistance vs temp. I can now calibrate the temp gauge with a SPDT switch.

[clbanman]

You asked what can cause the corrosion?  One possibility is:
http://www.myradshop.com/information/electrolysis.htm  Go down to the section below the yellow highlights for how to test your car for this problem.  More information:   
http://www.awrracing.com/media/electrolysis.pdf

http://www.frybrid.com/forum/showthread.php?p=44052

[Jettage1]

You asked what can cause the corrosion?  One possibility is:
http://www.myradshop.com/information/electrolysis.htm  Go down to the section below the yellow highlights for how to test your car for this problem.  More information:   
http://www.awrracing.com/media/electrolysis.pdf

http://www.frybrid.com/forum/showthread.php?p=44052

x2. 

[92EcoDiesel Jetta]

The coolant flange kept leaking slowly, until last week when I pulled it off for the 3rd (or was it 4th?) time and attempted to seal it again. The epoxy filling was still there intact, and the RTV in the previous attempt did not stop it from leaking. This time I used a Loctite gasket sealant that comes in a tube and is black in color. Very sticky stuff and tough after it dries. Used between a flange, it seals immediately. Resists oil, coolant, grease, diesel, gasoline, VO per the application engineer I spoke to. Anyway I put this stuff on both sides of the o-ring and seats between the plastic flange and head, torqued the bolts down and fired her up and ran it for the past week with no more leaks! I think the plastic (Meyle) flange is junk and deforming trying to press the o-ring down. Compared to the OEM flange that had a crack, the Meyle flange was thinner and not as strong. If the flange was aluminum, I'm sure I would not have had this problem.

One thing that baffles me is when the flange was leaking, the pressure gauge that I had hooked up in the upper hose to the expansion tank always had some residual pressure reading of a few psi's even after 5 days of letting the car sit. The coolant would leak the most after the engine was shut off and I would notice the level drop in the exp tank and coolant collecting on the nooks below the flange a few days later. Now that the flange no longer leaks, there is no residual pressure after the engine cools and the gauge returns to zero. Can anyone explain that? Makes no sense to me.