My experience with chasing temp to high
 

Thought I'd share a recent adventure with my 280GE and it's very germane to all, not just G-wagen owners.

Chasing a temperature gauge registering higher than I am comfortable with.

Symptoms: at idle temp slowly rises towards the right 3/4 mark. At highway speed, okay in the middle to 1/8 right. Confirmed with digital temp gauge. Been chasing it for awhile.

Cooling system condition. When I purchased the vehicle many years ago I knew that it needed a radiator and hoses. So all new plus new pump, deoil, decalicify, etc. Yes I can be picky, especially when I want to baseline a vehicle. Fan clutch checks 100%. All was well for a couple of years.

I don't like replacing stuff in a hunt so I've been patiently running various troubleshooting methods.

Last week I was working under the hood and caught a wiff of exhaust. Not a good thing. Looked and looked and couldn't find anything. So step one for me is to hook up my trusty shop vac at the tailpipe, and pump high volume low pressure air into the exhaust system. Made up a bottle of soapy water and went hunting. Didn't see any bubbles at first but when the solution ran under the exhaust manifold for the forward three ports BUBBLES!!!. I put my hand underneath and a very large volume of air was pouring out. Looked at it with a mirror and this was not a small crack.

Pulled the forward exhaust manifold and wow, there was a huge crack that had been previously repaired via welding. Frankly, I've never seen a weld job, even one done by the pros, hold forever on a manifold. I did notice that the manifold took a tug to get off. I found that the 6th bolt back was stretching port three back, which is probably how the crack manifested itself. Cast iron doesn't like stress. So that hole got reamed a bit to allow proper fitment.

I use POR-15 products a lot and decided to try their Fireseal 2000 manifold repair. A new manifold is $250-$350. (If anyone has one used for a 86 280 GE let's talk). I followed the instructions to the letter. So far so good. We'll see how long it lasts. Anyone ever use this stuff?

But the bottom line is, no more overheat. All of that very hot exhaust gas was pouring/pumping out and hitting the side of the block and then hitting the top right of the block where the temp sender is. And to make matter worse, the fresh air intake for the motor was most likely picking up some extra heated air.

Longest term problem I've ever chased.

I can't believe I went this long without getting carbon monoxide headaches. Says something for the cockpit sealing. Pretty tight. Scary though. Carbon monoxide is bad juju.

Where can I get some of that stuff? I have a cracked exhaust manifold on my 72 280 SE 4.5 and can't seem to find a manifold handy (the salvage yard crushed the one they had before I could get it off, bastards).

Pretty nice crack, but I think I can reach all of it with the manifold on, or should I remove it? I sure don't want to have exhaust up there under the hood!

I patched the block with JB-weld, and that seems to be holding (no long trips yet).

Peter

You can order it from http://www.por15.com/puttys.html

Based on m recent experience you'll want to pull the manifold. You'll need to drill 1/8 inch holes at the end of each crack to stop further cracking. Then you'll need to grind a small v groove. Then apply the material.

The material is surpising easy to work with and my first worry that it would run out before setting was not founded.

Best of luck.

And in the end.....
 

After a few months of use, a stress cracked formed right where it had been with the original in the casting. I knew in advance what had caused the original crack (manifold bolt hole spacing was too close, so I filed out some material and it fit fine.

However, I could have included a thin piece of metal screen over the crack when I used the POR-15 material. But I didn't

Decided that if I was going to pull the manifold for the 4th time (first was to weld, second was Fireseal, third was refireseal 'cause I didn't follow instruction) that I might as well install a new manifold. Fit like a charm. Original must have been bad workmanship by the OEM.

The second batch of Fireseal was impressive. I would not hesitate to use it and should I have to use it in an area where there is stress, I would certainly use the recommended metal screen. FOLLOW THE direcitons. My first mistake was to think I could add more material after the first dry. Not so. This stuff has to heat cure (not dry).

Best of luck to all who use this stuff. I'd be glad to help where I can.