The famous head crack on a 3C-TE

[spectra]

I faced the situation on my 3C-TE

Head got cracked on these spots.

I have been doing my research about the reasons for this but am unable to conclude exactly what causes this.

Need expert opinions

[PKTUN]

janab keya aap nitro use kartay hain high compression & overlapped valve timings ki wajah sai tou aysa nahi ho gaya hamary fleet k 1 shehzore diesel ka bhi aysa kuch haal tha 80000 km run k baad shehzor workshop in karachi said k yeag driver petrol mila kar chalata ho ga

am subscribing so i know what masters say in this respect

[spectra]

No nitrous or modifications were done. It was running on stock CT9 turbo. This happened gradually and all 4 cracks appeared one after another.

[spectra]

Also, Shehzore engine (Mitsubishi 4D56 adaptation) is not known for head cracking. Toyota 2L-TE in Hiace and Prados are famous for doing this followed by 3C-TE in Estimas.

[Xulfiqar]

the major cause of such cracks is high EGT as the area heats up, warps and cracks - high EGT is caused by too much advanced timing on a hot engine, hot intake charge and overfuelling either one or a combination of all - they are acceptable till a certain width, because after that these cracks open into the cooling gallery.

In some cases these cracks are also blamed of excessive coolant pressure while infact the coolant pressure is caused by badly sealing headgasket or stretched head bolts.

That is why I always speak of correctly timing a diesel engine with correct tools. Its not in human capability to measure by feel movements of 0.1mm increments.

[spectra]

This one is EFI and engine management is not fiddled with. Timing also not disturbed at any time. Can air bubbles cause this?

[Xulfiqar]

even with EFI the timing needs to be checked and adjusted with a dial gauge adapter anytime the timing belt is replaced or taken off.

you would need to have quite a lot of airbubbles to cause such heatup incident in your engine. btw is the cooling system overpressurizing? or do you have residual pressure in the cooling system in the morning?

[spectra]

There used to be residual pressure in the reservoir. Bottle used to develop leak often. On investigation we found cracked head. Dial gauge is not possible because that part of pump is flat its all ECU controlled.

[Xulfiqar]

Is this a singapore export model? the transmission this is using and the pump being fully controlled was on the singapore delivered models of the previa and lucida. The A/C compressor would be the toyota hiace variety. The american versions are spectacularly a PITA

anyway - as your cooling system is fully closed and not vented, I believe that you are telling me the presence of residual pressure in the cooling system after first depressurizing it then starting it with a closed cap and then checking after 2 minutes of running?

[spectra]

Residual pressure was tested same way as u suggested. Now head is replaced and all is well. No pressure of any sort.

[Xulfiqar]

install an EGT gauge in the exhaust, so you dont go into "cook" zone

[spectra]

Looking for a good one. Should it be placed before the turbo or after the turbo? Does that bring difference in readings?

[Xulfiqar]

always before the turbo

[spectra]

Ustaad jee, what is EGT threshold? I see it go as high as 750 if revved hard on a climb (like motorway salt range) or on hard acceleration (full throttle) Tested this on way to hospital with a dear friend having heavy bleeding after he had a glass c rash on hid hand. Haven't seen it go beyond that point though.

[SER_GTR]

High EGT Is Mostly The Cause Of Crack Like These........The Wall B/w Both Valves Is Quiet THIN And The HEAT Just Kill These Zones

Easily....!

High EGT Can Be Caused By Many Reason As Xulfi Bhai Stated....!

[Xulfiqar]

unit of measure please?

[spectra]

Unit of measurement is centigrade.

[Xulfiqar]

is this before or after the turbo?

[spectra]

Before the turbo on the point where 4 headers are merged as one.

[Xulfiqar]

its normal for a diesel to heat up when lugged, you could look into investing into a nice intercooler to cool the charge down.