Hello All,

First let me thank you for reading my post. I purchased this truck about 10 months ago, it has the I6 300 with the 4 speed automatic tranny. After about two months of highway driving, the exhaust manafold cracked. I had it replaced and about two weeks later it cracked again. I had a very good mechanic install this one, and he noted some difficulty in fitting the manifold to the engine, but he got it on, and he said he had to use some larger diameter washers in some areas. Now it is leaking again, litteraly burned through the gasket. my mechanic also noted that there is major discoleration ( blue and white) around the manifold. A little more history, I also, after replacing the second manifold, had the truck looked at, because it was running very rough, no choke, and burned gas like you wouldn't believe, and ended up having a new Carb put on. It had all the backfiring and loss of power and other things going on too. SO, Whew, With a new carb, new manifold, and some timing adjustments, the truck ran good, for those two weeks, NOW it is running like crap again, no power, burning a lot of gas, some very minor back fires, and the exhaust leak again. My mechanic is working on it right now to fix the leaks, but he said he has never seen this type of repeat failures.

What advice can you give me? I, and my mechanic, don't have a clue were to progress from here.


Any help will be greatly appreciated.

Richard Heitzman
Boerne, Texas
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Manifold loosening is part of the drill on these motors. I have to tighten the front three bolts/nuts regularly. I get an exhaust leak and an intake leak on number 1. Makes a crappy running gas hog out of it.

One fix is to pull both manifolds. Make sure the head is true and not damaged.

New studs or fix up a set of grade 8 bolts or a combo of the two. Locktight the studs with the highest grade stuff. Now I didn't do this, but it was suggested by a FedEx mechanic who had had his belly full of loosend 300 manifolds. Bolt the manifolds together and have them welded together. Then have the mating surfaces (to the head) machined flat. Then bolt it up as a unit, being careful about the torque sequence. A follow up re-torque is probably a good idea also.

2nd fix, which I do intend to try: Again, do the stud/bolt thing, and then install the EFI manifolds. Since these are two 3 into 1 units, they don't want to go pretzel like the long fellow you have now. Some minor mods may be required, but read through the threads here--lots of folks have done it. Search farther and find the part number of the Walker Y-pipe to complete your installation.

 

The new exhaust manifold that you had installed, was it and aftermarket, or did you get it from a salvage yard?

I bought an aftermarket once, and it didn't line up right, poor quality as far as being true. If you intend on using a stock manifold, I suggest find one from a salvage yard.

The other recommendation is go to EFI manifolds. 2 sets of 3 as oppposed to 1 set of 6. The 2 pieces are easier to get to seal, plus you don't have that mate up between the intake and the exhaust manifold, that seems always prone to leak.

I changed my truck to EFI manifolds, Offy intake and a Holley 4 barrell. It cost a good bit of money to do the swap, but I have been very happy with the results

 

Well folk,

My saga continues. Picked up my truck from the mechanic on saterday. It sill has the exhaust leak and running rough, plus now it is backfiring when I shut her down. It look like I am going to need to find me a serious mechanic who understands and is competent on these engines. If anyone knows of a great mechanic here in the Boerne Texas area and would recommend them, I would appreciate it. I am tired of throwing money at this truck and not seeing any results. ( plus my wife is about ready to kick me out of the house because of all the money I have spent).

Richard

 

You mention running rough, If I was to take a gamble I would say your intake is leaking as well. It is sucking to much air, that is why it is running rough.

 

To answer the previous questions, the manifold that is on the truck right now is an aftermarket brand-new one. I have followed everyones answers so far and it really looks like I am in trouble. LOL. What I am going to do is:

1. Find a good local, recommended mechanic.
2. Remove the exhaust and intake manifolds.
3. Investigate to see if the block is warped.
4. Investigate to see if I have a head gasket blown out.
5. Check timing, timeing gears for problems.
6. have the carb ( brand-new reman) set up again
7. service the tranny.

Put her all back together and see what happens.

All I want is a good running truck with minimum of problems. From what I can tell, everyone is saying that the I6 is bulletproof. From the way my truck is running, I am about ready to put a bullet in it.

Thanks for the help

If you know a mechanic in the Boerne Texas area, please let me know.

Richard