I've got a 2000 F-150 4.2L that seems to have a pinhole leak in the coolant bypass tube (?) situated in the engine valley just behind the thermostat housing. This is a 6" L-shaped aluminum tube that connects to a 5/8" hose that runs down to the top of the water pump. How to repair? Is this tube pressed in? Threaded?

Any advice/help on this would be greatly appreciated.

 

Welcome to FTE yippeerider! From what I have read on this forum, the tube is pressed in. The intake manifold should be removed to replace it. This is not all bad news, as the job will entail replacing the intake gaskets that are somewhat of a problem on this engine. Good luck!

 

Thanks, John... So I've got the intake manifold all the way out of the truck... Now what? How do you normally get that pressed in fitting out of there? And, of course, got any advice on pressing in the new one...?

 

Okay, so I'm feelin' pretty good tonight... I had the problem with the pinhole leak and today I seem to have dealt with that. Sorry to say I had to go to another forum for help, but found a guy who had patched the hole with no negative results for a year. So, today I rounded up a length of 5/8" heater hose and, with the help of some water-based lubricant (okay, okay, I'll tell you it was Astro-glide---borrowed it from my wife...) I was able (with no small amount of effort) to force it completely over the 6" long, 90-degree bend in the tube and right down to the engine block. I added three hose clamps and was able to effectively seal the pinhole leak in the tubing. Now, that being said, I've only run it for a few minutes, but there is no sign of a leak now. I'll drive the truck more this week and see if it holds, but I'm optimistic, given that another guy has driven his for a year with no problem, and his was even more of a hillbilly-rig than mine, since he actually split the tubing he was patching with and then clamped it into place, although he used some JB Weld first. For future reference, and, in deference to my Herculean effort to cure this problem, we'll call it the "Modified Hillbilly Rig". Patent law aside, feel free to use this method as the need arises... It'll save you about $850 (for the dealer to remove the old pressed in fitting and replace it with a new one, after removing the intake manifold), so it's certainly worth a try...!

 

Hate to admit it but used the same type of repair on mine. My bypass blew a pinhole after replacing the radiator. After doing some checking on the tube and cost of replacement, cut out the bad section, slid the heater hose on and triple clamped both ends.

It has now been about 6 months with no leaks. With nearly 300k now on the 4.6 '97' it is tough to justify the cost of replacing the bypass.

 

Charliebravo was the removal of your 4.6 intake a hard job?I have a pinhole leak thats hitting the back of the firewall just to the right of the 5/8 heatercore tube fitting.Is this the same leak you all are talking about?I was looking in my haynes manual and it appears that the there is a 1/4 hose and fitting running horizontally behind the intake.

 

Not hard at all. Follow the Haynes manual. Takes a few hours to remove. While you have the intake off change the plugs and anti-knock sensor. MUCH easier to do with everything out of the way. You will need the fuel rail spring clip tools to disconnect the fuel lines. The bypass tube on mine had a hole at the midway point on the bottom and could not be seen. Ran my hand along the bottom and found that there was just a rough spot. Cut out that section and found the hole.

The bypass tube runs from the back of the water pump housing to the rear of the block through the valley. At the back it turns left and up as looking from the front.

The overall job of removing intake, replacing plugs and knock sensor took about 4-5 hrs as I recall.

Good luck!

 

My leak seems to be a pin hole leak that shoots against the firewall slightly lower to the right of where lower heatercore hose attaches to metal tube.I think the tube has the hole near where it attaches to block. I have the Haynes manual and will see where that knock sensor is located.Is that a dealer only item?Is that 5/8 tube the only size running back there?

 

The knock sensor is located in the valley, and to change it you need to remove the intake. It can be had at Oreilly's or Autozone. That is a secondary issue. Change it if you pull the intake. If your leak is where you describe, you may be able to clip a piece of hose over the tube from the back without removing the intake.

 

I wish.My hands are too big,its real tight back there.Thanks.

 

I used jb weld on the pin hole leak I had. Did not remove the manifold, used a bent piece of wire to reach back to it. Been over a year now and no problems. Use a piece of emory cloth to clean the tube first. Hope this helps.

 

That exactly my plan.I was going to clamp it with hose over the JB also.Wow you guys must have small hands my intake is almost off now.My leak is from the lower tube behind block maybe yours was on the upper.My engine is the 4.6.

 

Did not even try to get my hands in there. The valley was full of coolant. Thinks the worst, was ready for the worst. Had all the gaskets, tools, plugs etc before starting the project.

 

ive got coolant coming out from behind the motor above the transmisson it feels like it may but from a metal connection peice in the back of the intake maybe ?? is this even close to the pre mentioned problem, cant really see or get my hand back there very well

 

this photo might help

https://www.ford-trucks.com/forums/8...d-on-5-4l.html