New head or rebuilt used head?

[TallGuy]

Hello everyone,

Happy New Year!

Just prior to Christmas, driving my loaded 1992 L300 (auto) over the Coq to Kelowna, the head blew (cracked). Prior to that trip, I had done a cooling system check as my upper hose had blown not too long beforehand. Suffice it to say, with the coolant loss it ran hot a few times. I wanted to ensure that the cooling system was intact, the water pump wasn't leaking, and the heat exchange was decent prior to travel. That and a new timing belt, I thought, was a good pre-trip service.

It was running great for the week prior to the trip; even on the trip it was running nicely with good power. Note that I do not have a pyro-gauge. The temp gauge held steady even up to the summit but on the descent I noticed it was running a tad hotter than normal. Coolant loss. A pressure test the following day showed leaking from the head.

So then, a new water pump & thermo, new rad, and a machined head, as the machine shop asserted the head wasn't cracked at all. Turns out it was, so the question is:
Do I get a new head (from Rocky Mtn.)? He has just imported 10, which gives an indication that heads are overly sensitive on the L300's. (I've heard this is true for the Pajaro's and the Tyota Hilux as well... Shouldn't diesels be designed to run hot?)... OR... Do I get a non-cracked, used head and have that machined?

I ask to see if anyone has any expertise/knowledge with this. I might imagine a new head, possibly made in China, going sooner than a rebuilt used one made by Mitsubishi. Who knows?

Anyhow, this is an unexpected and unfortunate repair bill.

Many thanks, as always...

[jessef]

Sorry to hear about your situation.

The L300/2.5 heads are solid. They do not have the same issues as the 2LT Toyota heads from overheating.

With that said, if your cooling system is not operating at 100% efficiency and you push the motor too hard (which is very easy to do), then you end up with broken bits.

I would recommend to get a new head from RMI and go over the whole cooling system prior to driving it again.

Either that or just buy a complete used engine from Mardy. Whichever is cheaper and easier for you.

Most importantly, I cannot stress enough that you install a pyro/EGT gauge to monitor the temps.

Most 2.5 cracked heads/blown rods/overheating issues are caused by the driver pushing the motor too hot and hard.

The stock temp gauge is useless.

Get a good pyro gauge and save yourself more grief and money down the road.

Good luck !

[MardyDelica]

hi, dont go with the replacement head if this is china or taiwan. get the original as the metal is soft when it made in china or taiwan.
not owrth to do the job.
if need help pls call me.
Cheers;
Mardy

[Green1]

I had done a cooling system check as my upper hose had blown not too long beforehand

To be honest, I think your head was already "gone" before this last coq trip, this trip just finished it off... the rad hoses usually don't "blow" unless there's a head or head gasket issue to start with. (the coolant system doesn't have much pressure in it unless you have a problem)

The heads on the 2.5L mitsubishi engines are "adequate"... by this I mean that they aren't the ticking time bomb that the 2L toyotas have (many dealers will tell you that on the toyota with the 2L engine it's not about "if" the head will crack, but when.) but the mitsubishi heads aren't indestructible like the mercedes heads either (now those are bulletproof!) you do still need to care for the engine, if you overheat, you will still crack the head.

My advice would be to get a good used head, and a professional install job. and probably a pyro gauge and a lighter right foot on the long steep hills.

[TallGuy]

Update:

String of Bad Luck...

My original head was re & re'd twice. After the first machine job in Kelowna it went back on then they noticed after some test miles that it was cracked. The machine shop insisted it was good when they finished the job... Precision Auto has a good rapport with the machine shop so the shop did a weld repair job and back on she went. More test miles and it seemed good to go...

I picked it up early March and drove it back over the Coq... Heater hose leak after I got back... Tightened hose clamp... Then white smoke the next day, out of the pipe. Burning coolant... Head is toast.

I'm not sure why they chose to repair the head... The word is these heads are sensitive. So it's probably best just to replace it with a good used one.

So now I'm left with an A/M head from Rocky Mtn. Imports or machine a good used head. I'm inclined to go with the latter given the metal softness.

Cheers... J.

[thedjjack]

I would go used head off an other original motor.

With a coolant leak the head runs out of coolant first! That head probably got very hot fast!

Also, Aluminum head on cast iron block = Very different rates of expansion rates. My rule for engines is to bring them up to temperature then drive them hard never push a cold motor it will blow up.

When I was younger had a friend who work at a dealer and they would blow up motors with rod knocks so they could warrenty the whole motor not just fix 1 rod (new car dealer). He said if it came in warm it would run all day with a brick on the gas knocking away at RPM limited of the exhaust system. But in the morning cold, few minutes after the brick hit the gas pedal...BOOM.

Warm up nice and slow and then go...