Diagnosing a whistling sound from the engine under load.
Our Ford F-150 is half of our home. Specifically, it's the half that can move our home! Because we tend to boondock in the middle of nowhere so often, without our truck we'd feel very isolated and vulnerable. We need it to be 100% reliable.
But last week it developed a noise. We had stopped to take a photo by the entrance sign at Great Sand Dunes National Park. As we drove away, it started making a strange whistling sound under acceleration. We only drove a couple more miles on road before we hit the Medano Pass Primitive Road - what would turn into an incredibly eventful trip, but that's a different story. We shared the full story on our Facebook and Instagram pages, as well as in our newsletter.
The next day, when we recovered the truck from the trail, I noticed it was making a ticking sound when I first started the engine. To be honest, my first instinct is there was some dirt or debris from the trail on one of the belts. Regardless, we had little choice but to drive the truck 140 miles back (the long way round) to the RV park, pick up the trailer and drive another 200 miles to Denver ready to drop off Diana's brother, Jānis, at the airport for his flight the next day.
The whistling sound seemed to disappear as the engine warmed up, and nothing else felt amiss - the truck towed fine over the mountain passes, with no apparent loss of power. Regardless, we called around several dealerships in the Denver area - the earliest appointment we could find was a week later in Silverthorne. I explained the situation over the phone and he suggested it sounded like a blown exhaust manifold gasket.
I watched a few videos on YouTube and the symptoms were identical: ticking at idle turning into a whistling sound under acceleration that would lessen as the engine warmed up.
Roll the clock forward a week, and yesterday I took the truck into Summit Ford in Silverthorne for diagnosis and investigation. The staff there were very helpful, and after 2 hours they gave me the prognosis.
Turns out I didn't have a blown exhaust manifold gasket. I had blown both exhaust manifold gaskets.
Sadly, from conversation with them, it sounds like a common issue - they see about 1 vehicle per week with this issue, and although most are Ford Transit vans, it's common on the F-150 too.
The issue is that the engine block and exhaust manifold header are made of two different metals - and hence they expand and contract at different rates as the engine heats up and cools down.
Although the front 2 exhaust ports on each side are secured with 3 bolts each, the rear port has just 2 bolts holding it together - this rear bolt is the weak point. If the engine gets really hot, as this twin-turbo 3.5L EcoBoost likes to do on the long climbs up I-70 towing a trailer, the stresses in the metal are enough to shear the bolt at the back of the manifold! And our truck had sheared the rear bolts on both sides of the V6 engine block.
In my opinion, this feels like a huge design flaw in the part, but sadly there's no option but to replace the two failed exhaust manifolds (plus gasket, studs and bolts) with new, identical parts. Fortunately all this work is covered under warranty.
Unfortunately, the earliest they can get the work done is in 2 weeks time! So for the next 2 weeks, they've advised us that we're OK to drive, but to stop if the problem worsens. Then I'll need to take the truck back in where they'll have it for 2 days - they need to lift the entire body off the frame to do the work!
There's no doubt that Colorado has been tough on the truck - towing a 7,500lb trailer up long, steep interstate climbs at high elevation (~11,000ft) in uncharacteristically warm weather (up above 80F). Even so, I'm somewhat disappointed that the truck couldn't handle this - after all, we're within all weights in terms of GVWR, towing capacity, and we're running on 91 Octane fuel as recommended.
Still, I guess these things happen. The true test is how well it's handled - although Summit Ford are booked up so we can't get the work done as soon as possible, their service so far as been great and I'm confident they'll do a good job. We'll find out in 2 weeks I guess.
Meanwhile, I've been ogling over the news that Ford is planning to release a new 7.3L V8 gas engine this fall in their Super Duty lineup - which is looking very tempting. Couple that with the new Tremor package on the F-250 which promises off-road upgrades, that could be a very interesting vehicle for us…!