3.0 diesel exaust tail pipe temp very hot

[bart351]

I've recently purchased a 94 3.0 diesel surf (first time of owning one) a week later and it was showing signs of head gasket problems, not overheating on the gauge but bubbling in header tank and starting from cold bubbling out of rad top on start up, none of these were showing when I purchased it. I took the plunge and removed the head for inspection, the gasket seemed fine but the head had several major cracks between valve seats and combustion chambers. Purchased a new AMC head and bolts good quality or original gaskets etc and rebuilt engine. The engine started on second crank and sounds fine there is no sign of bubbling or any water loss, temp gauge is showing ok and power is better, water flow looks good and rad was back flushed. The only thing that does not seem right is the exaust tail pipe temp seems very hot even after a short run you cannot even touch it and spit will bubble on it, is this normal I would expect this on a petrol engine but thought diesels ran cooler. May be just being paranoid after spending a lot of time and money on this new motor !

[tashtego]

I've recently purchased a 94 3.0 diesel surf (first time of owning one) a week later and it was showing signs of head gasket problems, not overheating on the gauge but bubbling in header tank and starting from cold bubbling out of rad top on start up, none of these were showing when I purchased it. I took the plunge and removed the head for inspection, the gasket seemed fine but the head had several major cracks between valve seats and combustion chambers. Purchased a new AMC head and bolts good quality or original gaskets etc and rebuilt engine. The engine started on second crank and sounds fine there is no sign of bubbling or any water loss, temp gauge is showing ok and power is better, water flow looks good and rad was back flushed. The only thing that does not seem right is the exaust tail pipe temp seems very hot even after a short run you cannot even touch it and spit will bubble on it, is this normal I would expect this on a petrol engine but thought diesels ran cooler. May be just being paranoid after spending a lot of time and money on this new motor !

Hi and welcome.
My understanding is that diesel engines run hotter than petrol ones. No particular mechanical knowledge, just thinking of the vehicles I've driven. Also I am thinking of the flammability of diesel: petrol lights up much more quickly. So, intuitively, I would say a diesel needs to run hotter to facilitate combustion. Hope my old physics teacher is not on the forum, in case I talking complete balls, as usual. My tail pipe is very hot, you definitely would not want to touch it, even after a short run. These engines get up to temp quite quickly.
Cheers

EDIT: well, after a quick poll here at work seems I was wrong. Guys here reckon petrols run hotter. But diesels seem to have bigger rads...? Oh well, no idea mate. Still your hot tail pipe shldnt be a problem.

[boma23]

might be an idea to fit a decent aftermarket water temp guage, as that's the one you need to worry about really.

if exhaust is genuinely too hot, might it have been changed for a smaller (e.g.) custom one? i've read ideally these engines breathe much nicer and run cooler with a 3" exhaust from the turbo back... I've currently got one from a V8 Nissan Frontier pickup bodged onto mine

cleaning and / or doing the EGR mode properly may well help

[tweak'e]

fit an egt gauge as well as water temp.
one of the problems with the 1kz is egt's are a bit hot for the head to handle.

[bart351]

New system fitted from Roughtrax so should be ok. Not to sure about monitoring ex gas temps, coolant temp I understand and will be fitting a aftermarket temp gauge to keep a check on it.