Just the thermostat gasket or more?

dgeist · **Posted:** Sat Jan 31, 2015 12:57 pm

So, I've been nursing a small leak in my cooling system for some time now (possibly over a year). I've checked multiple times and it's only on the outside and is manageable with periodic top-offs. When I finally got a chance to add some fluorescent additive and chase it down with my UV light, I found it was not where I though it was...

Turns out, the leak is originating near the front of the block just over the front the the exhaust manifold. There's actually a small pool beneath the thermostat housing:

So.. I need to get in there and pull the thermostat. Thankfully, i have my custom remachined unit from our pal (currently) down-under that's been waiting for a rainy day to install. what I don't know is if the other residue in the area indicates an additional leak or just "wicking" along the exhaust manifold and the seam of the head/block. take a look:

In the second pic, the area above the housing that's glossy is fresh. The additive turns green in UV light and it was fairly sunny out. The only spot along the head gasket that showed any coolant was right near that spot, so I'm hoping it was just a symptom of having some spray out from around the leaking gasket and not a greater problem.

Thoughts?

Dan

gmctd · **Posted:** Sat Jan 31, 2015 1:14 pm

Your seam of particular interest is between the head cover and head, not the head\block seam which would be beneath the exhaust manifold - your leak is somewhere above the head, as in heater hose connections, T-stat hose connections, T-stat housing, viscous heater, radiator hose, etc

Hi-pressure wash the engine in that area, blow\let it dry, crank it up and observe as engine temps increase

dgeist · **Posted:** Sat Jan 31, 2015 1:59 pm

The engine was still warm from the last run cycle and the only spots that had any wetness on them (or any green tint from the dye) were right at the thermostat/head junction and then below that pool that has formed. There's some green-tinted items down below, but I suspect that's due to having been dripped on for some time. I'm going to replace the t-stat housing after a good clean water rinse and hope for the best. I think that's the most likely culprit. what have folks used in the way of RTV on that joint? I don't trust the wafer gasket except on a factory clean/smooth mating.

Dan

papaindigo · **Posted:** Sat Jan 31, 2015 3:33 pm

I would strongly recommend against a hi-pressure wash. Way to high a risk of getting water into critical electrical connections; much high then in the olden days when all one had to worry about was the distributor and spark plug connections. A garden hose rinse is quite sufficient followed by a brief run of the engine, around the block so to speak, to start drying.

I suspect you are right about the leak source but would recommend that when you replace the tstat you also replace all the OEM hose spring clamps with stainless steel worm clamps; at least for the spring clamps you have to remove to change out the tstat.

I uses a bit of Ultra Black RTV on ones I've done but mainly to hold the gasket in place while I got the tstat bolts in place.

FYI if you have not already done this in my experience bits of the old gasket tend to stick to the aluminum head. A "safety" paint scraper razor (http://www.thepaintstore.com/American_L ... -04481.htm) does a good job of removal but be careful as the aluminum head surface where the gasket seats is easy to scratch.

Hexus · **Posted:** Sat Jan 31, 2015 3:38 pm

I used a small die grinder and a light wire brush disk to clean mine. Then I used the Wafer gasket as well as a small smear of black RTV to hold it in place.

I've used the black RTV twice as that's what people wanted done, and had no issues reported yet.

I have heard of many using simply the black RTV, and having no issues.

dgeist · **Posted:** Sun Feb 01, 2015 10:28 am

Thanks for the input, guys. I gave it a good hose-rinse and then put everything back together yesterday so I can order some fresh parts and do it right later this week. I don't want to drain ALL the coolant, and most of the hoses appear to be in good shape, so I'm going to get new ones that actually connect to the t-stat body (with worm clamps) and just clean the rest. I may just do some high-temp grease to hold the gasket in place. It shouldn't mess with the sealing properties of the wafer like RTV (could). With a clean and unscathed surface, I'm sure the surface prep and bolt torque matter more than anything else.

Also, I noticed in Squeeto's write-up, there appears to be a little hole just above the exhaust manifold where it bolts to the head:

What is that (drain hole for accumulated scree, perhaps?)? It is suspiciously located RIGHT where my little pool of coolant was in the above pics, so I want to ensure that's not a potential leak source, but rather something intentionally designed as a drain, etc.

Dan

gmctd · **Posted:** Sun Feb 01, 2015 11:27 am

Appears to be a drain relief - it's external, so try running a piece of baling wire down between the head and exh manifold
FYI: I dug around in mine, found no thru-passage - looks sorta like a freeze plug

Just the thermostat gasket or more?

Who is online