I have a 97 4.2L with 76K. It has been losing coolant with no obvious leaks under the truck. It will also start rough until I apply some gas and then it runs fine with no misses. The oil pressure will also drop intermittently after running for a while when I idle. At this point, I think I have the issue with the intake gasket leaking. I wanted to be pretty sure before I took it to a mechanic to have the gaskets replaced. I looked at the oil in the bottom of the oil pan by draining a little out and did not find any coolant. The oil on the dipstick is also the correct color - no milkshake. My next step was going to be removing the spark plugs and checking for coolant in the cylinders or on the ends of the plugs. I have also read about pressurizing the system with the plugs out for an hour and then cranking the engine to see if any coolant is expelled.

Any thoughts on the next steps or other suggestions would be greatly appreciated. I am not a mechanic but am comfortable doing some poking around the engine with Haynes manual in hand.

 

Your engine/timing cover can leak too. Check for dampness around the water pump and below where the timing cover seals to the block.

 

Sorry dude but sounds like you are yet another victim of the dreaded hydrolock issue that these motors have. The following are the gaskets that will need to be replaced if you don't want to h-lock your motor. Upper & lower intake gaskets, timing cover gasket. Get the ones from Ford not the Felpro ones. Cost for the gaskets is about $100, cost of the repair...about $1000. Cost me about $1200 to get mine done.

 

Yes that engine is about to hydrolock. Flatbed it to a dealer/mechanic and get those gaskets changed before you bend a rod or crack the block

 

Update: I was able to confirm with Ford that 99B29 was performed on the vehicle in 2000. By my understanding, that should have replaced the timing gasket. That would mean my leak is most likely the intake gaskets. Please correct me if I am thinking wrong here.

 

A leaking timing cover gasket will not hydrolock a motor. It will either leak coolant into the crankcase, leak coolant externally, or leak oil externally.

Your problem sounds more like a lower intake manifold gasket leak. You might pull a few plugs and look for evidence of coolant being burned, and/or coolant in the cylinders. With a little searching, you can probably find out which cylinder the manifold gasket is most likely to leak into.

 

Roger that. If necessary to have the gaskets replaced, the TSB says to make sure the EGR ports are clean. I also saw a recommendation to clean around the IMCR as that may get stuck with years of gunk. I will have a shop do this work, so I wanted to take care of any other possible issues while they have the intake off. Any other recommendations of things to do/look at are welcome.

 

Update: No obvious signs of coolant found on any of the spark plugs. A friend has a leak-down tester so I will be using that this week on each cylinder to see if I can diagnose the source of the leak. I have not used one before, but it seems pretty straightforward if I can get the hang of finding TDC.

 

The leak-down test did not show any significant leakage on any cylinder. I pressurized the system for about 4 hours and removed the spark plugs and then hand-cranked the engine. I was able to see a small amount of coolant leak out of cylinder #1. As I was working around the engine, I also saw where the passenger side of the timing cover gasket is leaking again. This supposedly had the 99B29 repair performed, but it looks like the timing gasket is failing again. Planning to take it to my mechanic to have the gaskets replaced and hopefully solve the issue for good.

 

Had an independent mechanic replace the intake gaskets and timing gasket with the new Ford gaskets. Also had the water pump replaced since they were taking it off anyway. The intake gasket was leaking in cylinders #1 and #4. The timing cover gasket was fine and did not actually need replaced. I did see coolant on the outside of the timing cover when I was working on the truck. I have to think this was an external leak from the intake gasket that ran down the front of the engine? Anyway, hoping this does the trick and the truck is good to go.