Mystery coolant leak

[johnunit]

I've inspected repeatedly for cracks. there are no cracks or significant pits, and it is leaking from right past the gasket surface. I think this time was again partially the fault of getting stuff gooped in the bypass hole, causing excessive pressure. I will try not tightening it down quite as much before letting it dry.

The partshouse I went to today had no The Right Stuff, or I would have bought it. It's the standard stuff at the custom shop I worked at briefly and it seemed to work well. I did, however, find some stuff specifically for thermostat housings and water pumps, so I'm going to try applying that and leaving it overnight before putting coolant in. After that leaks I'll probably see about getting a ride to a speed shop for an o-ring housing. I assume they don't require modification to the intake side? I didn't get a housing for my 4-barrel intake so I guess I sort of needed a new housing anyway.

[1987cp]

Yes, the longer you can wait before topping off the coolant, the better. I think the nominal cure time for Ultra Black is 24 hours, but I've had good luck with doing it in the afternoon and then letting it sit overnight, maybe 12-16 hours.

I'm sure you know, you never "need" to buy a new T-stat housing unless your old one is damaged.


As far as O-ring necks, I'd forgotten about you Kanucks not having AutoZone handy ... but before getting a ride, try calling around to see who can order one for you if even they don't normally stock it. Can save several oodles of headache that way. You'll probably want to ask for them by PN only, as IIRC nominal applications are 1969-1976 model years or some such stupidity.


I think these are the two PNs I'm familiar with:

Mr. Gasket 2662 -- http://www.jegs.com/i/Mr.%20Gasket/7...0002/-1?CT=999
Spectre 4232 -- http://www.summitracing.com/parts/SPE-4232/


Amusingly, this Summit search revealed several way to spend LOTS more on your SBF water neck if you so choose!
http://www.summitracing.com/search/M...?Ns=Rank%7cAsc


Oh, and here's the replacement O-ring from Mr. Gasket. Good to know about, since typical parts goons seem to think it doesn't exist. Probably other brands have one available as well. http://www.summitracing.com/parts/MRG-2669/

[johnunit]

sweet. if I dump coolant on the driveway tomorrow I'll give a call to Karbelt in Pickering with the Mr. Gasket number. It's more than a little annoying that in a city with a metro population north of 5 million there's exactly one general performance parts place in the city proper, and about 4 within an hour's drive from me...

I realize I don't ever "need" a new one, but the current one has that funky temp sensor that switches from ported to manifold vacuum advance, and is aluminum, so it would look more than a bit odd on an iron-intake holley-topped engine.

Thanks a bunch Mike.

[johnunit]

just updating this

I got it fixed a while ago.
I used the thermostat specific RTV. I also was more careful about getting all the coolant out of the intake I put it together and tightened it just enough to create a consistent seal all around, and using relatively little RTV (that stuff is expensive anyway). I then left it for about 20 hours and then tightened it up and filled it. It's held through about 1000KM of driving, lots of high-rpm blasts and stop-and-go traffic.



I think a big part of my problem before was using too much RTV and resulting in this:



As you can see, the crossover is mostly blocked, and this is almost impossible to tell from the outside. I believe that this was causing the pressure from the water pump to blow the RTV out around the crossover, but the pressure was relieved when the t-stat opened, causing my issue of finding evidence of a leak but no actual leak after some of my failed attempts.


Thanks for the advice in here, I'd probably still be washing the driveway with a 4000lb blue-and-chrome sprayer if it werent for this.

[GM_Guy]

Yeah, you'll want to go a lot lighter on the liquid gasket. =-) I would only put on a thin bead around the neck (and around the bypass hole) and slap it on, and then let it sit for as long as I had time to wait before refilling.

Alex.

[johnunit]

yep, that's pretty much the summation of what I learned lol.

[1987cp]

Good job getting that fixed up! As is probably obvious, I still remember pretty clearly how much headache my chronically-leaking water neck caused me back in '97 or '98.