Hi Nodge. thanks for the excellent info as always. If it is not a PCP issue, then it is interesting that the 1.4 does not seem to suffer from the same problems.
IF it was a thermal suction issue (with partial collapse of the intake circuit ducting) then I am (at the moment) at a loss to understand how this could be ?
The 1.4 would (IMO) surely 'suffer' the same thermal circuit hose / intake depression / or to look at it another way - atmospheric compression due to a reduced internal pressure differential. Are you saying that it is simply the inability to circulate the coolant to adequately cool the engine ?
The pressure differential in the coolant circuit would be - more or less - the same - apart from the increase in temperature necessitating greater thermal transfer.
If that is the case, then why does the KT not
still suffer as the thermal differential due to massively increased PCP cause the system to overload (
if - as you say - the flow rate through the system is 'inadequate' or 'marginal' at best ?)
This scenario does not add up to me.The increased PCP and hence
massively increased thermal transfer requirements in a super / turbocharged unit would require a
very verygood coolant system. BUT - If - as you seem to be eluding to - the system is barely adequate - indeed - just about comfortable - / marginal - then at massively increased PCP, the only logical assumption - in this hypothetical discussion would be that the cooling system is superb ! - and any issue with the warm up phase and pressure differential issues- are 'causing' issues - and not afterwards - !!!!!!! . IF the system is perfectly OK for a massively different PCP hence massively different thermal transfer needs then flow inside the physical structure of the water passages is simply excellent - to say it is not is simply not logical. One cannot have one without the other.
IF there is an issue in warm up phase due to recirc' / blockage issues then that is one thing - however - trying to say a coolant system has issues due to passage way issues etc is totally contradictory when you look at the far higher PCP and thermal transfer needs of the T unit.
IMP _ It really DOES NOT add up
It really is illogical.
Joe
K series cooling issues are complex and many.
The HG doesn't fail at the fire rings. Well it does, but only because the coolant level has dropped. So fire ring failure is a secondary result of coolant loss.
Coolant loss is a result of the breakdown of the elastopolymer bead applied to the stainless steel gasket substrate. The elasto basically delaminates from the stainless steel.
The primary reason for elasto delamination is movement between the stainless and the alloy of the head/ block castings.
This was originally attributed to the head being located to the block with plastic dowels.
Later post 2000 engines were fitted with steel dowels. However gasket delamination still caused HGF, albeit after a few thousand miles more than before. The later thinking was delamination occurred due to expansion differences between the alloy block/ head and the stainless gasket substrate.
The engine has always has cooling system issues. Not with the cooling capacity being to small. The cooling system capacity is overly large for the engine. This coupled with some design issues means the engine doesn't warm up in a nice smooth ramp. What happens is the temperature climbs rapidly from cold to well over the thermostat open temp. The stat opens and coolant flows from the over sized rad, through the stat and quenches the block. This is cooled rapidly due to its low mass and low coolant volume. This cool coolant then hangs around in the block in various stagnant pools, before making it's way through the badly cleaned out coolant ways in the head.
Simultaneously the thermostat has now had time to react to the deluge of cold coolant that passed through it, so it closes again, cutting off the flow from the rad. The engine temperature now sores again and the over hot, quench cycle is repeated, over and over again, until it reaches an equilibrium.
Now let's look at the thermostat it's self. This is the standard stat, not the PRT.
The thermostat is on the return from the rad. It blocks off all flow from the rad, unless it's open.
The thermostat is a conventional wax stat with the normal sensing bulb.
Because the stat is in the return, the bulb has a dedicated flow of coolant directed at it via the bypass circuit. This is the next problem with the design. The pump draws on the thermostat bulb end of the stat housing and the bypass pipe fitted to it.
The bypass is connected to the top of the head and is supposed to circulate the coolant round the engine. However when the engine is revved hard, the pump can outstrip the flow capacity of the bypass circuit, causing the hoses to collapse inwards. This substantial reduction in flow compounds the coolant stagnation in the block and accelerates warm up massively. However because the flow of coolant past the stat bulb has now reduced, it reacts slowly and engine temperature sores once again. Then the stat opens and the block is quenched once again.
This continually cycling engine temperature is what causes the gasket's elastopolymer seal to break down and fail.
If the engine was to warm up in a smooth temperature curve and stay there until shut down, then the HG would last much longer that it actually does.
There are some installation factors that change the working life of the HG. For instance, in the MGF, the bypass circuit is very long. This is why the HGS in those seem to fail at very low distances. Coupled to the fact that sports cars are often driven hard when cold. The HG life is seriously reduced when driven like this.
I think that's it. Hopefully it explains some of the problems with the design.
