View Full Version : Coolant leak

09-13-2004, 02:38 AM
I helped my friend pull his engine today. 1997 Cobra, about 100K miles, stock engine.

The car was spewing coolant and steam out the exhaust system. When the engine was off, coolant we peeing out the mufflers. And the coolant reservoir cap was removed.

After pulling the head, there was coolant in cylinder 5 (forward most cylinder on the driverís side). Upon inspection of the deck, head gasket and head surface, we could find no signs of a coolant leak path.

When we looked into the exhaust port, we noticed that one of the valve guides was wet. We think coolant is leaking down this guide.

What are the chances of this? Is the valve guide in a dry bore or wet? Has anyone ever heard of this happening? Is this repairable?

Any comments welcome.


09-13-2004, 07:10 AM
The probable bad news is that you may have a cracked head. Either that or the head was defective from the factory. More than likely, the head probably had a weak spot when it was cast due to trapped air in the casting.

09-14-2004, 02:02 AM
With the coolant ports all taped off, the head was filled with water and the cam rotated to open the exhaust valves at cylinder 5. Water began seeping out at the valve seat/runner interface. We are pretty sure the valve seats are not exposed to the water jacket, so we feel it is a casting flaw. Any opinions if this is repairable? The thought is remove seat, TIG weld the seat area, machine a new seat counterbore, insert new valve seat, machine/lap the new seat. Seems plausible. We'll be getting a second opinion shortly.

09-28-2004, 05:07 PM
The head was taken into a local engine shop. Shop says they have seen this problem before (not necessarily only on Cobra heads). It is repairable (TIG) and they are working on it.

10-24-2004, 12:12 PM
We are done with the repairs. The head came back from the shop. They TIG'd(Heliarc) the area around and between both exhaust valves, machined and pressed in new valve seats. They cleaned up the whole head and threw everything back on. One interesting tidbit, some valves will be open (when they are not suppose to) after reassembly due to the lifters holding things up. This is normal per the engine shop and will settle down (i.e., close normally) after engine startup. The engine reassembly went without incident. All new head bolts and headgasket. All replacement parts were stock. Before starting, we cycled the ignition serveral times to build up fuel pressure and cranked the engine over a bit to prime the oil system. Reconnected the coils and fired it up. The engine started with a little bit of valve clatter, which went away quickly and the engine settled into a amazingly smooth idle.:thumbsup: :D There was a lot of white smoke (steam) from the exhaust because all the coolant was still in the mufflers. This will burnoff after a good long run. No check engine light!:D No coolant spitting our the exhaust pipes and mufflers.:D Took the car around the block and everything is functioning normally. Had to top off the coolant but that's it. Very cool!:cool:
Again, this is my friend's car and I started this post to try to get input on the initial problem. If you ask me a lot of questions, I may not be able to answer, but I'll try.:) THE COBRA IS BACK.