94 3.1 td exhaust mani warped

[rally4life[mike]]

Hi guys
I have been going through the loads of info that there is on the Isuzu bighorn 3.1 exhausts and manifolds. but this was only after my first encounter with a Isuzu, if only I knew there was all this info on these trucks, my truck developed a exhaust leak and after I took off some heat shielding I found the old sheared bolt sitting in the heat shielding. So I drilled out the old bolt [ I used a air drill these are quite compact and fit in the gap easily] then used an easy-out to take out the old bolt. Got new gaskets and put back together and found I still had a leak , after Throwing all my toys out of the cot I realized I should have checked the manifold with a straight edge and now have to go through the toucher of taking it all apart again, that brings me to my question what was the cause of the warping of the manifold in the first place? Obviously the EGT got way to high but to what cause

Thanks to you all Happy skids ;D
Rally4life

[geeves]

Interesting question for which I doubt anyone knows the answer. Its always one of the back bolts that breaks and one bolt broken shouldn't cause a leak in the short term although heating and cooling with inadequate support can cause the warping which then causes the leak.
First guesses are a design fault in the heat shield or stud but if this stud is the same as the rest we can discount the stud, A fault in the assembly process. These things are assembled by machines so on badly set up machine would mean 1000s faulty engines.
These engines also have a name for overheating and cracking heads although nowhere near as bad as a certain other brands diesel engine.
Do we have a diesel mechanic on board who might be able to through more light on this

[rally4life[mike]]

I have read on another site [sorry cant remmeber which one read so many lately] that having a exhaust system that is failing or to resrictive ie wrong muffler fiftted can result in increased back prassure and the follow on from that is a incress in maifold tempurture. this makes sence but!!!!! That is why I am asking here. By the way this site was and is the most helpfull site on the mighty Isuzu, thanks to all that have given tips and info in the past!

[geeves]

That is true. The famous 2LT has its problems more than halved by fitting a 2.5 inch exhaust. Consensus here is to fit a 3 inch system to the 3.1 and 2.5 to the 2.8 although the 2.8 has very few probs in NZ anyway although a definite performance increase is noticed

[rally4life[mike]]

The one other thing i have noticed is carborn deposits on the inlet manifold by the EGR which so I have now learnt can be blocked off with out to much hassel, i tow a rally car with my Isuzu and always felt it was quite up to my expectations of a 3.1 turbo mainly on cruising, just the slightest of hill and the auto wants to drop out of overdrive I dont go off road much as this is the family car as well but "she who must be obeyed" lets me do the shiney runs when they come up which is not to often in a AKL ----hey maybe a club day trip to get to met some other members in the top half of the north island?

[geeves]

You may already of done this as it applies to all autos used for towing big loads. The fitting of an aftermarket auto trans cooler will stop the auto overheating and add years to its life. If I was fitting one I would fit it in parallel to the factory cooler in the radiator rather than in series. The reasons are that heat from the radiator gets the auto to correct temp quicker which makes for smoother gear shifts and it reduces the risk of blockage which isnt realy a prob on Isuzus but is on Terranos which use much the same box