Knocking noise when over 80 degrees after 15 min

My '03 Ranger started making a knocking noise last summer after 15 minutes of driving but only when the temp. outside is over 80 degrees or so. It stopped during the cold months but has resumed this summer. It is a low knocking sound and a) the vehicle must be moving, b) it has to have been moving for 15 minutes or so and c) it must be over 80 degrees outside. I can feel it under my feet and thru the steering wheel but mechanics say that they don’t hear it and can’t find it because they are getting into the vehicle after it has had a couple of minutes to cool down. Mechanics tell me that they have checked the universal joint and that it is fine. I need a brave mechanic to drive along side of me in another vehicle, going 45 miles per hour for 15 minutes and then they need to jump over into the driver’s side and take over the wheel (like in the movies - haha) so that maybe we can find what is making the noise. Can anyone help me? It makes this noise whether the vehicle is in 4wd or 2wd or the A/C is on or not.

does the truck pull right or left when going down the road or braking?

This may be far out, but I wonder if your problem could be a motor mount. My other guess is that there may be something in the exhaust system that allows the pipe to knock against the floor.

@wesw: Yes, it pulls to the left! What do you think this could be?

I had a similar prob with my jeep and just successfully fixed it.

it was a combination. I don t know which came first or which caused the other but I had to fix two problems

first, I don t know if, your ranger has u- joints on the front axle or CV joints? if it has the the u- joint, it may need replacing, im not too familiar with CV joints, but they may have the same effect, IDK

second, my brakes were dragging, due to stretched caliper pins. IDK if the dragging brake caused the universal joint to fail, or vice-versa

I replaced the caliper pins (4.99 a set) and pads on both sides, and replaced the one bad u-joint and now the jeep handles like a dream. I can let go of the wheel and it goes straight and I can stomp the brake with no pulling.

I also inspected all the steering and suspension stuff (luckily it was good, except one broken sway bar bolt which I just welded back together)) and greased everything while I had it up and apart.

You Tube had videos of the repairs (jeeps are popular) and I had a repair manual and the guys here helped a lot.

hope this helps,wes

some times its hard to tell if a u-joint is bad until you relieve the tension, I could not tell mine was loose until I had been hearing the noise get worse and continue for a couple months

the mechanic you used could have done more to check what the prob is, anything that makes your car shake and clunks should be investigated for safety.

also, check your tires carefully all around for bulges indicating a burst steel band

Has anyone checked the universal joints?

@wesw and @the same mountainbike: thx for yr responses and suggestions! Coincidentally my colleagues have recommended that the u-joint be checked. I have had 3 mechanics check it only to say that it is fine…I may just replace it anyway. @Triedaq: Thx for your response and suggestion…I will have motor mounts checked out this week.