Overheating / Overheated Riddle - What happened?

[spannercrab]

So over Christmas, while towing a 2t camper up a hill in CQ, I sucessfully managed to completely hand grenade my gas-injected TD42 Intercooled Turbo engine - pistons and rings have become one entity, so compression loss is severe on 3 cylinders, and bores are somewhat scored; hence full rebuild required. This aside - I'm still trying to piece dogether what heppened ... any ideas appreciated.

1) Was running pretty hot, drank 3L of coolant on the trip there, but no excess pressure (in fact no pressure of any sort) in the radiator. Circa 45 degree day ....

2) Drank another 3L of coolant in the next few hundred km, but completed the trip and side trips etc. without overheating or other problems - no furthur leaks / mysterious disappearances until the trip home. Coolant remained full (and wasn't running as hot - possibly due to no load)

3) Temp started to climb on the way home, but never reached the upper mark (not the top upper mark, the one underneath that which I used to take to mean "upper operating limit")

4) Radiator cap was replaced just in case this was the mysterious reason that the system wasn't building pressure. Can't remember what the coolant recovery tank was doing at this stage.

4) Checked the coolant level only a few minutes (10 minutes maybe?) before the engine let go. It was full - or at least was to the top of the radiator cap (again, no pressure in the system, even though temp gauge was 2/3 of the way up the scale).

5) No evidence of damage to head after she was stripped down (at least not yet, it's being crack tested as I speak), it almost seems as if there was still water in the head.

6) Looking through the hole into the water jacket where the oil cooler assembly is, I've noticed some distinct mineral deposit lines about halfway up the bore liners - seemingly as if the water level has been about halfway up the liners and the line demarks the point where the water was boiling.

7) Definately no evidence of external system leaks. No water in the oil, no steam, no marks on block etc to indicate system leak.

8) Radiator is now going to be replaced anyway because it's in pretty poor shape - i.e. crumbling away

8) Coolant overflow was full to the point of overflowing (at time of engine failure) - not sure how this is directly related to the problems.

9) When the sytem was drained post incident, there was maybe 5L in it? Around 2L came out when the radiator was drained, the rest was in the block (came out of the turbo coolant feed). So low coolant was the root cause - even though the system appeared to be full only a few minutes earlier.

10) There is no evidence to suggest water made it into the cylinders - i.e. no discolouration on pistons etc. Piston protrusion is normal.

11) Head Gasket looks to be intact with no bypasses or breaks


So, the obvious question to ask here is - where did the water go?

How is it that there was no pressure in the system, even at 45 degree heat pulling a load up a hill when the system was obviously low on juice, which should have increased system pressure to nearly an extreme point?

How is it that there was water in the top of the engine / radiator - but there was a "steam void" in the bottom? (this is the only logical conclusion I can come to based on what I've seen)

I am yet to test the LPG converter, heat exchanger and cooling system for pressure loss, but there were no obvious external leaks in these components.

[300WinMag]

Have you tested the termostat and checked if the water pump is leaking?

[spannercrab]

WinMag,

Have not check the thermostat as yet ... it LOOKS really shiny tho'

No leaks that I could see from the water pump - weep holes were dry and nothing around the gaskets ...

[300WinMag]

Hows your hoses and are there any pinholes in Radiator. If it is not holding pressure there must be a leak some where. Mine was leaking out of one of the bolts that holds the thermostat housing on. The water was pushing its way up the thread and coming out the gap in the spring washer took me forever to figue it out as it only leaked when on hwy. I saw the trail of coolant coming from around thermostat housing. Anyway theres lots of info here if you search overheating lots of tips. Make sure you put bigger radiator in. Good luck.

[spannercrab]

Thanks Winmag - as soon as the engine goes back in, I will definately pressurise the system to make sure there are no leaks.

As you say, all signs point to a leak but I just can't think where there could be a big enough hole to release all that energy!

[IN24BZ]

i work for a nissan dealer , rarely see a problem with a 4.2 , altho they did have a bit of a run of overheating at one stage there was a buliten on it , the viscous fan coupling if i recall correctly needed to have oil added but anyhow... the things i see here that ring alarm bells is " So over Christmas," the hottest time of the year.... " while towing a 2t camper up a hill in CQ, " Two tonnes uphill " gas-injected TD42 Intercooled Turbo engine " Gas injected..... thats probably a recipe to hand grenade anything especially if the air con was on... i might be wrong but with a already semi borderline cooling system that might have just been a bit much... unable to explain coolant loss but cracked block or such maybe but thats highly unlikely.

[coxy321]

Almost sounds like a water pump failure to me. Very strange. Have you checked the water pump yet? Or the viscous fan coupling as IN24BZ mentioned?

[spannercrab]

Viscous coupling ... I have heard various stories about the coupling to the point where people have somehow retrofitted (cough cough) Toyota 1HZ fans / coupling onto their TD42's ... not sure how easy or difficult this is, or even if it's a good idea. The fan "seemed" to lock up the last time I looked at it, but then again I wasn't really paying much attention at the time.

I don't think it was the water pump it seems to be ok ... both belts intact and the impeller (beautiful stainless steel job - assuming this is factory) is firmly attached to the shaft.

IN24BZ - point taken re: overloading with gas + turbo @ 15psi with fuel to match - and yes the A/C was on, towing a 2T camper on a 45deg day ... if everything is not working just right ... well ... I already know the rest

[AJS]

Do you have a boost and EGT gauge? If so, what were the readings at the time? And did you still have good oil pressure at the time? I know that with my old GQ, when we were in the Pilbara, once the temp got up to a certain point, I would see the oil pressure start to drop on the aftermarket gauge, which to me meant time to slow down. I was always worried that lower pressure would mean less, or thinner, oil getting to the pistons and valves.

May be worthwhile checking the oil pump anyway.

[spannercrab]

I have both boost and EGT - boost was running around 13psi and EGT was sub 500degC, oil pressure was also fine (around middle of the gauge, no sign of sagging etc.). The only thing that was up was the engine temperature gauge - and even then not to the "upper operating limit" mark.

I just got the results back from the machining place I use, and pretty good all things considered:

No damage apart from normal wear and tear (plus the obvious pistons, rings & bores)

Head was ok - not even warped, decking not required, no cracks
Block is ok - no deck required, no tunnel bore required, no cracks
Crank requires grinding to 25 thou due to factory grind tolerances
Cam is ok - polish only
Tunnel is ok - polish only
Rods are ok - polish only

Pre-comp chambers need to be replaced (x6)

Valve guids are worn - need replacing (x12)


+ the usual welch plugs, bearings etc ...


My theory is that it seems as if the water only "went missing" in the top half of the cylinder liners - i.e. the head was still being cooled, but there was a "steam void" in the hottest part of the engine - i.e. around the upper liners

I'm nearly sure all this is related to the system losing or not being able to build pressure which led to the void around the top of the liners. If I can find the hole, then I've found the cause of the problem. Shouldn't be too hard to pressurise the system once it's all back together.

[stokedapollo]

new hoses all round????

[spannercrab]

Haha ... yes, quite possibly.

The radiator height is mismatched to the engine because of a 50mm body lift at the moment, so I may end up making up some solid pipes in 316L to get the "required" fit ...

[bogged]

1) Was running pretty hot, drank 3L of coolant on the trip there,
2) Drank another 3L of coolant in the next few hundred km, but completed the trip and side trips etc. .

I would have parked it there.. cars dont drink 6ltrs of coolant in 2 days without good reason.

theres a small drain hole on water pump that dribbles out coolant when the seal goes...

did the engine bay smell of coolant?

[spannercrab]

Not sure bogged, there's a few interesting smells in my engine bay

I'll have to admit I didn't specifically pay much attention to the weep hole, but I had a pretty fair look all around the place and didn't notice any coolant stains etc. down the front of the engine / timing covers etc.

I'll be sure to check when it goes back together. I'm hoping that if I pressurise the system to say 15psi, any leaks will show themselves up.

Although I agree, it's something that probably should have happened before I needed to rebuild the engine. Expensive lesson I suppose.

[bogged]

I'll be sure to check when it goes back together. I'm hoping that if I pressurise the system to say 15psi, any leaks will show themselves up.

If I was spending thousands rebuilding an engine, I'd spend a few hungs and replace the water pump even if old one was good. Cheap insurance.

[ozy1]

Haha ... yes, quite possibly.

The radiator height is mismatched to the engine because of a 50mm body lift at the moment, so I may end up making up some solid pipes in 316L to get the "required" fit ...

wow i knew a bloke who had over heating dramas, he tried it all, ended up lowering the radiator and all his dramas were gone, yes he did have a fan shroud,
remember this if it still overhgeats when its all up and running again,

[its aford not a nissan]

as for what happened , i recon you boiled the coolant ,even though the temp guage read ok , with out it being pressureized there will be hot spots in the head and possibly the turbo boiling the coolant , but when mixed with the rest of the water circulating in different parts of the motor it cooled down again to give a reading of below " too hot "

my theory anyway

[macneil]

I'll be sure to check when it goes back together. I'm hoping that if I pressurise the system to say 15psi, any leaks will show themselves up.

If I was spending thousands rebuilding an engine, I'd spend a few hungs and replace the water pump even if old one was good. Cheap insurance.

i got my pump for 130 at bursons.. not really that much epecially if your rebuilding.. mines only a second hand engine and im still not taking risks..

[IN24BZ]

i did read somewhere about the fitment of a 1hz fan to a td42 i cant recall where but , however the nissan buliten lists a toyota part number viscous fan coupling oil to fix a nissan problem... ill dig it up tomorrow at work... .. ps keep your eyes off my 1hz its so slow id be making my getaway and you would still have time to steal my fan

[bogged]

however the nissan buliten lists a toyota part number viscous fan coupling oil to fix a nissan problem... ill dig it up tomorrow at work..

Toyota P/N 08816-03001.

[azzad]

I'll be sure to check when it goes back together. I'm hoping that if I pressurise the system to say 15psi, any leaks will show themselves up.

If I was spending thousands rebuilding an engine, I'd spend a few hungs and replace the water pump even if old one was good. Cheap insurance.

i got my pump for 130 at bursons.. not really that much epecially if your rebuilding.. mines only a second hand engine and im still not taking risks..

Genuine are about the same price; I was suprised when I bought mine.

Dazza

[IN24BZ]

[quote="bogged"][quote="IN24BZ"]however the nissan buliten lists a toyota part number viscous fan coupling oil to fix a nissan problem... ill dig it up tomorrow at work..[/quote]Toyota P/N 08816-03001.[/quote]

Check mate..... =) see i wasnt going silly

[bowtie landie]

I'd test the thermostat BUT replace it anyway.
If it wasn't building up pressure then it was definately releasing the pressure (and coolant) somewhere.
If the thermostat wasn't opening fully then you could end up with overheating in the engine, and higher pressures. Coolant loss maybe through a pinhole in a heater hose - usually spraying onto a hot engine and evaporating almost instantaenously, whilst retaining good coolant levels below the cap. Let it sit & settle for a while & you'd probably find that it would have taken another 3 litres.
You can have a brand new pump but if there is restriction to the coolant flow then the heat can not escape quickly enough into the coolant and overheating will occur.

Peter K