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Discussion starter · #21 ·
Memorializing what I found today. The thermostat original OEM is 66 1/2 mm diameter but it fits in a milled out female area in the housing on the engine block, at least for the 96 and beyond models, at 69 mm. The net effect is the thermostat left to right up and down is loose by several millimeters. Also, when you mate the thermostat housing on to the engine block in this location there is several millimeter gap inward that houses is the thermostat. If the thermostat has no seal around it it will vibrate left right up-and-down, but also if there is no gasket or seal in front of or behind it, it will jiggle forward and aft by several millimeters in each direction. Needless to say, the gasket needs a rubber seal around it that wraps over front and back, a cross section would look like a C. What I found out today is that seal when wrapped around the OEM thermostat is 71 mm total. The seal without the thermostat in it is exactly 68 mm and fits Inside perfectly. When you put the thermostat in it due to the interior dimension of the seal itself it stretches to 71 mm. This presented a conundrum. I spent time with my Dremel tool literally milling the OEM thermostat down to millimeters in order to have the assembly fit within the female housing on the head. this way the thermostat housing meets directly up to the head with the gasket in between and you don’t need to force it. What happened in my case was a prior mechanic jammed the thermostat in there with the seal around it and used the four bolts to seal the assembly which cut the seal and resulted in the photos above. done properly, what I did tonight, is the thermostat with seal should mate inside the female housing before you put the thermostat cover housing and gasket on it. Hope this makes sense. If you send your car off to get a new thermostat done by a mechanic I guarantee you he didn’t take these extra steps.

The first photo shows the thermostat with seal does not fit properly. The second photo shows this more clearly. The third photo shows the seal itself fits perfectly inside the female housing on the header.

as is clear to me, my car had a clutch job done with the prior owner at 10,000 miles and I suspect they replaced the thermostat with an OEM thermostat but the seal did not fit. They jammed one in there that failed. This explains why I have some new OEM hoses in the coolant system and some original OEM hoses. My belief is the one that blew forward of the engine between the firewall was original 1997.
 

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Discussion starter · #22 ·
I have on order OEM belts and hoses because while you are in there for this project particularly at the thermostat is a perfect time to do the belts. My belts look like they’re starting to dry on the edges and get cracked which means they are ready for replacement.

I studied and studied and studied again if there was an easier way to do the belt replacement than having to disassemble further the vehicle. The answer is no. Off came the wing and then the muffler heat shield and then the aluminum top and bottom coolant pipes and tomorrow I think I will have to take the transfer bar off all in order to get visibility and 17 mm wrenches in this area in order to get the belts replaced. lambowebb.com has a great write up on replacing belts but the author assumes these things have already been removed. I don’t see a way to do the belt project while leaving the muffler heated shield in place. On top of that, the triangular bracket that the engine cover with the bull logo and firing order attaches to should be removed. If you remove that bracket you will leak coolant everywhere because it sits on the screws that hold the flange for the water pump, which is why I decided to do this belt project while my coolant system was disassembled.

The first photo shows the flange with 90° elbow in place that I simply put back finger tight in order to prevent anything from dropping into the water pump. Notice underneath the missing coolant hoses which provide access for your 17 mm spanners. The second and third photos show how tight the dimensions are between the 17 mm nuts at the power steering pump and The distance you will have to gap in order to get the belts free. I thought long and hard about removing the power steering hose in this location to make things easier. This of course would have presented its own problems with leaking power steering fluid all over the place so I opted to leave it in place and use thin 17 mm spinners.

this entire area needed cleaning so I spent time spraying it all down with multiple sprays to test. I must say of the many I tried I was equally happy with purple power and griots engine cleaner. This is messy, tedious, and good old-fashioned TLC.
 

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Discussion starter · #23 ·
Of the many photos I’ve seen of diablo
Engines, I have noticed different hose colors and it’s driving me crazy. Note my own hoses in the center part leading to the water pump were gray but the new OEM hoses received yesterday are this color. I have seen blue, gray, black, and now orange!?!
 

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Discussion starter · #24 ·
Now also notice the OEM hose that burst on my car, between the engine and the firewall, when I bought it a few weeks ago came out of its original OEM package in a slightly grayed, almost fuzzy condition. (First photo). My order yesterday mistakenly included the same hose again, OEM from the factory in its original packaging, (second photo) but it came back in perfectly good shape and with what looks like the heat shield on it. This leads me to believe the second photo is actually a Murciealgo hose but it’s the same part number OEM from the factory. I already replaced that hose up by the firewall and given the scars on my arm (!!) I am loathe to replace that hose again with what arrived yesterday! I suppose I now have a hose on spare which I will replace proactively again one day if I have an engine out. It is just odd that OEM from the factory can deliver two hoses in dissimilar condition.
 

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Discussion starter · #25 ·
So that this is all memorialized in one thread, see also these notes regarding changing the belts.
 
Discussion starter · #26 ·
My beautiful Sunday was just fine until I started smelling coolant coming out of Clyde. Remember that hose that I replaced in this thread last year? THAT one!? Well, I must not have gotten it all the way on the impossible to reach, horribly narrow, arm-slicing, Italian-curse-word-inventing, incorrectly angled metal pipe nipple in between the firewall and the front of the engine ... because it just vibrated off. I write this bored out of my gourd sitting on the side of the road waiting for the flatbed. This car is going on a one-way trip to Josh at Veloce to have this hose fixed because this time I’m going to pay him to shred his own arms. 😡

courteous reminder to every Diablo owner: have that hose fixed proactively!
 
Jeez. What an utter horror. Sounds like every attempt I make at fixing anything on a car. Good luck and let us know how Veloce manages to fix it (hopefully without pulling the motor!)
 
Discussion starter · #29 ·
Veloce here in Kirkland Washington really is great and knowledgeable and gives excellent service. Josh has been on the phone with me all afternoon to ensure I got the car safely to the shop, and that’s on a Sunday. Great customer service.
 

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Discussion starter · #30 ·
Four hours labor, which sounds about right to me when it’s up on a lift. Josh was able to get the hose back on from underneath the car whereas I tried it from under on jackstands and on top after having removed the bonnet. Back together!

Look what was right ahead of me on the next rack. Clyde’s twin.
 

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Look what was right ahead of me on the next rack. Clyde’s twin.
Oh! Looks to be three Diablos even! Clyde's twin, and what looks to be a silver 6.0 in front of the 360.

And I wonder if this is very similar to the coolant hose problem with the Murciélagos. I mean, likely so because of the engine being carried over, but you know what they say about assumptions! More importantly, hopefully this problem stays fixed for you for many years to come.
 
Discussion starter · #33 ·
The other cars in the shop were not there for the same reason, but Veloce does many Diablos and Murchies. Every time you take an engine out you should replace that hose. Period. And yes, Murch goes or at least early ones had the same issue. I believe, but I’m not certain, that they changed the design in later models but I’m not sure.
 
You got caught by the hot-dog algorithm. Nice write-up. My Noble has a large turbo in a very small place and destroyed all its coolant hoses and wiring with some modest-trackwork. I use DEI shielding on all exposed hoses now.
 
if anyone is contemplating this job in the future, here is another tip in addition to what Mark has written up.

remove exhaust and all components from header back.
remove rear diff bolt
remove two main engine mount bolts.
remove front transmission mounting bracket and drop down shifter box

with this done, you can rotate the engine backwards by jacking up the front gearbox (put wood under jack to protect casing).

this will give you plenty of access to the offending hose in question.
 
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