GT-40 Over Heat Temp Indicator

[farmerandy]

While running at about 2500 RPM in my 1996 Super Sport and in fairly rough water out on Lake Bridgeport (TX) yesterday, the over temp / low oil pressure light came on. This was preceded by the engine sputtering as if it was running out of gas (which is wasn't). While searching the instrument panel for an indication, I saw that the water temperature was just over 200F and the over temp indicator light was on. This sputtering only went on about 10 seconds before I shut her down. I then opened the hatch and heard popping that sounded like metal expanding under heat. The exhaust manifolds were very hot. After letting it cool down for about 10 minutes, the engine would not even turn over when trying to start it although the starter was attempting to turn the engine (i.e., there didn't appear to be some sort of electrical protection interrupt circuit preventing me from starting the engine). I haven't changed the water pick-up impeller in two years. Did I have a total melt down or is there something minor going on here?

[Erik]

RE: GT-40 Over Heat Temp Indicator

Definitely change that impeller immediately, clean out the waterpump housing and basically give it a thorough cleaning. I did the same thing to my boat yesterday. I overheated it twice but it only briefly got to 200. Total bummer. I am told that Fords can take an overheat better than most, so you are probably ok. As am I, I hope.

[farmerandy]

Update

Update: I took the drain plugs out of the engine block and manifolds and what appeared to be normal amounts of water came out of both. The water was clean and didn't appear to have any oil in them. Also, I just changed the impeller and it was definitely in need of changing. The vane were all there but chipped and pieces missing. Additionally, it appears that the inner spline shaft was spinning inside the impeller mating rubber spline; at least you could hold the impeller and turn the belt pulley and the impeller would clock on its spline.

Additionally, the oil on the dipstick is clean and full and from that brief inspection there doesn't appear to be water in the oil.

The engine will still not turn over this morning. I'm going to pull the spark plugs next and see if the engine will turn absent of any compression resistance.

[farmerandy]

EXTREMELY BAD NEWS: Removed one spark plug and it had water on it. OK maybe it's just the heads. Nope, drained the oil and water and lots of it came out.

Where should I start looking for a short block?

[farmerandy]

Whoops sorry, I need a long block. Suggestions?

[richard]

GT-40 die

Your problem may not be serious, think this way: it may be manifold leak, change the manifold and riser and use new gaskets,

[farmerandy]

Well my sons and I spent the day pulling the engine and taking it down to the block and valve assemblies. The cylinders were full of water. But there was no oil in the tops of the pistons. I think this is indicative of blown head gaskets? A couple of the valves looked warped. The cylinder walls don't appear scored but are rusted. The engine turns by hand with about 10 ft-lbs of torque.

Anyway I've got the block and valve assemblies in the back of my truck and will be taking them to a machine shop on Tuesday. What all should I do with the engine stripped down to this level (e.g., timing chain, cylinders honed, etc) The engine has 340 hours on it.

[farmerandy]

OK I've determined the root cause. Both housings that bolt on top of the exhaust manifolds had one broken bolt each. We thought that we broke them while getting them out. But on further inspection, the failed surfaces are completely rusted over so they didn't break yesterday. So water has been spilling over at this interface down the exhaust manifolds, into the heads and down into they cylinders. Also the insides of the exhaust gas portions of the manifold have serious amounts of rust in them. My theory is that over the winter the gasket got hard and dry and while using the boat for the first time this year it just didn't have any sealing capability at all. We had been running the boat at idle for about 15 minutes before the failure, so there wasn't enough heat to boil the water off and the cylinders finally just filled up with water to the point that the engine died.

I'm not going to take the block apart now that I think I know what happened. I'm getting the heads checked to make sure the valves are all OK and I'm getting the exhaust manifolds pressure checked to make sure there's not an oil water path internally.

Thanks to Richard for making me think this through. Probably didn't need to remove the engine but hey it was fun.

[farmerandy]

The more I think about this, I'm not so sure that water in the exhaust manifold could get into the pistons. The only time the exhaust valve is open is when the piston is coming to TDC. Any water that would try and get into the piston would be pushed out. Hmmm.

[nms1991]

The water leaked in after shut down of the engine causing the hydrolock condition, but still have the cylinder heads checked for bad valves and being cracked. Also check the surfaces where the exhaust risers mate to the lower manifolds for staightness and retap the bolt holes and if the bolts have any amount of wear of rust on them replace them with new bolts. Also use the newer style PCM riser gaskets that are graphite based as they seal better than the oldert style paper gaskets.

[farmerandy]

Thanks NMS1991. I've got the heads at a machine shop getting checked. Good suggestion about the manifolds and risers; I'll get r done.

From a visual inspection of the block and the ease of rotation of the crank, I plan on going back together without taking it down to a bare block. Thoughts?

[DavidF]

Make sure the connecting rod(s) are not bent from the engine being hydrolocked.

[farmerandy]

I got my boat back together and except for a couple of small hick-ups, it's running like a champ. Nothing like pulling and engine, tearing it down and getting it back together successfully to give one a great sense of accomplishment. Thanks to those of you who made suggestions. :grin:

[surroundsound64]

Good to hear!

Did they have to machine the heads?

[farmerandy]

No just cleaned them up real good and made sure the valves were still sealing.