Cast Iron Cylinder head

[glenn]

Why not use cast iron for the cylinder head? Why aluminum? If it is simply cost, then I'm sure every L300 owner in the world would pay that much more for some piece of mind.

A quick scan of the L300s for sale in delica trader shows 3 for sale with cracked heads (mine makes 4) plus at least three with brand new heads, out of 49 Vans. I know there are waaaaaay more out there with the same thing. That is a terrible track record.

I joke that the aluminium cylinder heads are a consumable part that should be replaced every couple of oil changes. So, I am very interested to ask the Delica hive mind - WHY!

[legionnair]

I agree I think only the isuzu big horn has a cast iron head. But it also comes down to proper cooling I am in the process of installing an electric pusher fan which will replace my AC fan with manual override and keeping my mechanical fan. I am also going to find a thermostat with a way lower opening temp. So this little motor is not running so warm.

I would love to source a cast head then you could ramp up the boost and get some more HP out of it.

Dustin

[thelazygreenfox]

Guys
The aluminum cylinder head is not the problem! Also lowering the operating temp is not the solution. All diesel engines run hotter when you give more fuel. It's the nature of burning diesel.

The cooling system does not deliver enough cool water to cylinder three and therein lies the problem. The block and head don't have large enough cooling water passages to cool the block and head. Additional cooling water travels around the block via a stainless cooling line, through the 2 heater cores and then to cylinder three but there's not enough total flow.

The additional cooling is a cheap alternative but the existing block and head should have larger internal cooling for the fuel consumed. Possibly you could increase the water flow in the bypass cooling line. A larger size stainless line or an inline water pump to increase flow may help.

The thermostat is partly at fault cuz it diverts all the cooling water into the bypass line when the engine reaches operating temp. The overall cooling design is flawed but it's still a well loved vehicle.

In case you didn't know I owned an L300 before I bought my gasser. The gas engines have the same type cooling but they burn a more controllable fuel. Again not perfect but I like it.

tlgf

[legionnair]

I will have a look at what you suggested but more cooling is always better. But you would have to agree a cast iron head would have been better that way you could ramp up the boost and get better power out of them.

Dustin

[glenn]

The question still remains for me. Why did/does mitsubishi continue to produce an engine with such a weak point? If it is as TLGF says, shouldn't this have been engineered out soon after the weak point was evident? In my opinion, if you drive a vehicle like a granny, you should not have to suffer such severe consequences.

I have never, never, ever had my van even up to the half way point between C and H. I'm afraid to open the throttle all the way, so never do. If I see even a hint of smoke, I back off immediately. I keep my rpms low. I don't travel over 100km/hr and typically cruise at 90. I know, I know, an EGT might have given me more info, but is it really this fragile? Is this a van that is more suited to idling in Japanese traffic rather than actually going on extended roadtrips or doing any work?

I'd be curious to know if any drivers with an EGT gauge have cracked their heads. I've heard it said that a head crack doesn't always occur as a result of a single overheating event, but rather they develop slowly over time - anyone have opinions on this? Anyone even considering pulling a trailer of any kind behind their L300 should seriously reconsider their choice of vehicle. I know I'm venting here, and many people haven't cracked their heads, but my van has made me sad - I used to really love it.

[nxski]

There actually was someone who racked a head and had an EGT gauge. While driving in hot temperature the EGT's can remain low while the water temperature spikes. Also, you say you keep the RPM's low, is this even on uphills? You'll find the EGT's spike quickly on uphills at low RPM's and you can damage something before you'll notice the change in water temperature.

I plan on towing quite a large trailer behind mine when I return and am well aware that I may crack my head, if this happens I will gladly swap in a different diesel engine that provides more power and stays cooler. In order to try to prevent this I will use my pyro and water temperature in conjunction to make sure the engine is at a safe temperature.

What I've found out from letting a few people drive my van is that despite saying they are very carefuly not to accelerate too quickly etc, they still drive the vehicle far too vigerously for my liking. I'm not saying that you do this just that this may be the cause for so many cracked heads (people beleiving they are driving carefuly while not doing so).

I too would be interested to know why Mitsubishi never did fix this weakness though, it doesn't fit with the reliable reputation that Japanese vehicles in general have.

[glenn]

Ultimately, I cracked my head, I know. I am the only one who drives the van. I'm just saying that it should be able to handle the occasional "spike." Like I said, the water temp has never gone to the 1/2 way mark, so any spike would have been very brief indeed. I feel like I'm driving around in a model A sometimes. Lot's of people like to drive a classic vehicle - but I thought I was buying relatively modern engineering. Sigh.
It would be interesting to know just how many of us have cracked their heads though, wouldn't it? Although I suppose that wouldn't really do any good to anyone. Better off to just get an EGT gauge, and drive really, really slow and be very vigilant.

[FalcoColumbarius]

I'm sorry to hear about your cracked head, Glenn ~ but for what it's worth...

ManitobaDeli brought up a good point about warming the engine up, whether sub-zero or hot weather and I agree with him. Even though I push her from time to time ~ two things I remain consistent about: Every morn I warm her up for about five minutes ~ until the needle moves, which means the thermostat has opened up and the block & head are going to be operating at temperature before I put any stress on her; secondly, I let the glow plugs cycle, even when the engine is warm. We're talking about three seconds here, not a long time.
I also whisper sweet nothings to her, which some people think odd but there you are ~ I suppose it takes all kinds... grins.

Falco.

[Diver]

Sadly there doesn't even need to be an overheating event, the head cracked on my 4M40 returning from a camping trip last month. The cooling system components are all in top order as is the coolant mix. I have a low coolant alarm and a digital temperature gauge with the sender in the top hose. The temperature never went above 94 C at any point yet coolant was being forced out the expansion tank overflow. Next morning started from cold and the expansion tank is a jacuzzi but still no overheating, probably could have kept driving it for a fair while with the cap removed.
By contrast, last year while driving my (older) Toyota Townace at 120kph, the three month old radiator fell apart and dumped all the coolant and the engine had died before I even realised what had happened. The alloy head didn't crack or even bend, just the head gasket blew.
I guess Mitsubishi diesels are just not that good when compared with something like a Toyota

[konadog]

No cracked head for me in 90 some thousand kms. No pyro either - and I tow a trailer regularly. I had the full deal refit done when I got it and that included an overhaul of the cooling system. I've not given overheating much thought since other that to go easy up big hills and
so on, but that suits my driving style just fine. I never do long warm ups either and think that's just a way to waste fuel. And I don't think my bus is remotely under powered - it has heaps to spare IMO.
Sorry to hear of your grief Glenn - I hope you get your bus sorted out find the love again...

[legionnair]

The question still remains for me. Why did/does mitsubishi continue to produce an engine with such a weak point? If it is as TLGF says, shouldn't this have been engineered out soon after the weak point was evident? In my opinion, if you drive a vehicle like a granny, you should not have to suffer such severe consequences.

I have never, never, ever had my van even up to the half way point between C and H. I'm afraid to open the throttle all the way, so never do. If I see even a hint of smoke, I back off immediately. I keep my rpms low. I don't travel over 100km/hr and typically cruise at 90. I know, I know, an EGT might have given me more info, but is it really this fragile? Is this a van that is more suited to idling in Japanese traffic rather than actually going on extended roadtrips or doing any work?

I'd be curious to know if any drivers with an EGT gauge have cracked their heads. I've heard it said that a head crack doesn't always occur as a result of a single overheating event, but rather they develop slowly over time - anyone have opinions on this? Anyone even considering pulling a trailer of any kind behind their L300 should seriously reconsider their choice of vehicle. I know I'm venting here, and many people haven't cracked their heads, but my van has made me sad - I used to really love it.

On hills you must keep you rpms high let her rev, this does one of two things makes the engine move more air that fuel lowering combustion temp and it makes the watet pump and engine fan spin quicker providing more coolant for the engine.
I see you have never driven with a pyrometer you must try it your driving habits will totally change. On the other hand the stock temp gauge is not a good indicator of water temp it does not react quick enough.

Dustin

[thelazygreenfox]

Guys
The temperature sending unit and the head crack are far from each other. There is a slight correlation to guage temp, pyro temp and head cracking temp but you'd need to install a probe at the no. 3 cylinder to check the real temp that the head cracks at.

Mitsibishi wasn't the only company that altered a gas engine for diesel use. Volvo and others did the same. Many mechanics replied then it wasn't a good idea. When aluminum heads first were used on gas engines they warped and blew head gaskets. I still maintain it engine cooling was the real problem.
tlgf