Maserati V8 engine health questions - comp results & pistons photos

A lot of thanks to all of you for stepping in and providing insights. This was super helpful and put me on the right track, even if I took the longer path. I am now happy to report that the problem has been identified and is being taken care of.

As you know I started replacing almost every component of the cooling system that was prone to failure, all hoses, O-rings, hose clamps, caps, etc. but that didn’t really fix it. At that stage I was suspecting a small and harmless compression leak past the head gasket(s) resulting in bubbles appearing in the cooling system. I say “harmless” because this never led to an overheating episode so the risk of damage to the engine remained low.

But over time the amount of water that was being lost at every drive started to increase and become a concern. I could not reasonably continue to drive a car that loses 4 liters of water over a 200 km trip, even if it does not overheat. I have been intrigued by many of your comments pointing at how tiny the overflow tank is, compared to the whole cooling system capacity.

This is where I made a little detour. I designed a header tank to address the shortcomings of the original overflow tank. Key features include 3.8-liter capacity, an outlet directly connected with the lower radiator hose to allow water recirculation, a tangential inlet paired with barrel shape to achieve swirl effect and separate air from water, and a float level indicator to monitor the level. The tank was fabricated by Allisport in the UK which did a fantastic job (I’m happy to provide photos and measurements here if someone is interested). The inlet was connected with the small port below the radiator cap. For good measure I also added an overflow tank to collect extra water that might be pushed out, if any. It worked beautifully and exactly as intended: bubbles of unknown origin were still entering the cooling system but they were continuously being pushed out no while water was lost anymore, and the whole system kept under operating pressure at 0.5 bar per the book. The radiator level warning light stopped turning on altogether, meaning that at any given time the radiator was full of water top to bottom. I also replaced the cap with a Stant Lev-R-Vent cap with a small lever for easy venting of extra pressure.

I was thinking of this as a medium-term solution, since the bubbles would need to be addressed at some point and/or if their volume increased substantially, but the new header tank was supposed to buy me enough time to diagnose the issue, find a competent workshop, and continue to drive the car without worrying about radiator level.

One of the things that prevented me from a definitive diagnosis was my inability to perform a consistent and repeatable block test (chemical test for CO2 in coolant). This is because with the original set-up, expansion and contraction of coolant was quite jittery with some air being pushed out, then air sucked back in, then pushed out again with a drib of water, etc. I constantly had to make sure that no “outside air” was being sucked in through the tester while avoiding water contamination with the chemical product… but now, I simply had to put the block test on the overflow tank and slightly lift the pressure cap lever to get a nice and clean (“free of water”) stream of air through the block test. And this made it very clear that the gas that was pressurizing the cooling system was 100% combustion gas, consistently making the block test turned bright yellow every time.

I decided there was no point mickey-mousing it any further so I delivered the car to Franco Tralli in Bomporto, a specialist featured in the Classiche Masters book, who seemed qualified for this job.

Still wanting to live dangerously, I drove the car myself to Bomporto some 400-kilometer away from Rome, 50% for the pleasure of the drive and 50% to see how the car handles itself. The trip was uneventful for the first 300 km, but the water pump seal failed near Firenze and caused a continuous stream of water leaking through the weep hole on the water pump. That’s a tiny hole so the leakage rate remained manageable, but I’ve had to top up about 5 liters of water for every 30 kilometers during the final part of the trip. I nonetheless made it to Bomporto safely and the water temperature never exceeded 75 degrees Celsius during the whole trip. Fortunately Mr. Tralli had just received a new stock of water pump seals and bearings from a US-based friend of his, so they will be able to rebuild the pump in no time.

His team will be pulling the heads next week and let me know their diagnosis and proposed course of action at that stage. Best case scenario, this is an ordinary head gasket leak requiring an ordinary head service. But when discussing over the phone and again when I met him this morning, Mr. Tralli kept telling me that his fear with these engines is a drop in cylinder liner level. He reminded me that cylinder liner protrusion should be positive by a few thousandths and that it sometimes happens that a cylinder gets lower than that into the block, which requires much more work than a regular head service. I hope that’s not the case but for the sake of curiosity do you have any experience of thoughts about this cylinder liner protrusion concern? The WSM says that the tolerances are from 0 to 0.010 mm so of 0 is an acceptable value, that means it would be fine if the liners were flush with the block. But I trust Mr. Tralli and his experience if he says they need to protrude.

 

Thanks for the replies, I won't have the opportunity to watch him work since I'm in another city but he still sends me some pictures.

Both heads were pulled yesterday and the amount of damage seems limited. At first sight, the mechanic did not find any obvious crack, and liner protrusion appears to be right. He's waiting for the machine shop to measure things more accurately but seemed confident, so if everything goes well this might be no more than a "normal" head gasket failure. More on that next week.

Below are a few pictures sent by the shop. The head gasket leak is distinctly visible on the edge of cylinder 5 in the first picture, in keeping with what was already visible from the piston pictures earlier on this thread. Interestingly, compression results for that cylinder weren't particularly bad.

As mentioned the water pump is also getting rebuilt and the impeller looks in good shape.

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Here is a quick update. The liner protrusion is a bit on the lower side but within tolerances for all cylinders. The right bank is fine. On the left bank there are 2 cylinders where there is a protrusion imbalance when taking the measurement at 2 different locations on the same cylinder, but apparently still within tolerances. Addressing this properly would require pulling the engine out. See attached pictures for more details.

However the workshop considers the issue is not critical enough to justify a full engine disassembly. They recommend proceeding with the heads service and head gasket replacement.

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The workshop called me yesterday evening, everything is back together and the car is running fine. The mechanic drove it about 20km to warm it up and he only found that the water temperature is running a bit low according to him, at about 70 degree Celsius. I told him I had just replaced the thermostat and that that's where it used to be since I purchased the car so more likely the sensor is out-of-calibration. He will test-drive it more extensively next week and if everything goes well I'll pick it up next Saturday.

He also strongly recommended rodding the radiator and re-painting the heads so I said OK. I was initially reluctant about the rodding because I had flushed the radiator at least 3 times over the past few months and the car never overheads, but judging by the picture I was clearly wrong. The existing paint was so bad every time I removed a spark plug I think I was dropping cracks into the cylinder.

A few photos and a nice video.

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All is well that ends well. I drove my car from Modena back to Rome this afternoon, and as far as I can tell the workshop did a top-notch job. The engine never purred so smoothly, it feels like new. Acceleration is smooth and powerful, temperatures and pressures are where they should be.

The engine job list includes:
- heads removal
- checking cylinder deck height
- valve removal and lapping
- heads resurfacing
- pressure testing heads
- valve clearance adjustment
- timing chains tension adjustment (they checked the length and ensured they had not stretched)
- new Elring head gaskets
- new Viton valve stem seals
- repainting heads and camshaft covers in correct black crinkle paint
- carburetor adjustment

For peace of mind they also replaced the thermostat (even though I told them I had replaced it only a few months ago) and the radiator temperature sensor. As mentioned they also rebuilt the water pump and rodded the radiator.

I also have to say that their invoice was VERY fair. I was impressed to get such a low price given the shop's reputation and expertise.

It really feels like the end of a cycle for me... It's actually been a year and a half now since I first noticed the symptoms of what was later diagnosed as a HG leak. I still have a few more projects for this car (upgrading rear suspensions is at the top of my list) but I don't think I will be starting anything major in the next year or so. For now I just look forward to enjoying some hard-earned reliability!

 

Hi Tony,

I have been there and been through exactly the same reasoning. The cooling system design is unique but if you have pressure build-up in the radiator, switching caps won't change anything. Pressure will build up in the radiator instead of building up in both the radiator and the expansion tank, and water will still continue to overflow. It will accumulate for some time in the tank giving you the impression that the issue is solved, but when the tank is full it will overflow on the ground.

My suggestion would be to investigate the cause of this pressure build-up in the first place. It may not necessarily come from the engine. A leaking hose clamp upstream of the water pump, where pressure is low, will suck outside air in the system, were it will be trapped once circulated through the water pump. A chemical block test showing the presence of CO2 is also helpful - you've probably seen my report, in hindsight this was the only test which confirmed the presence of a HG leak when most other tests (compression, leakdown etc.) didn't show anything abnormal. I would strongly suggest doing it, there are cheap kits on Amazon which are more than enough. In my experience the best location to perform this test is at the neck of the expansion tank, when the radiator (non-pressure) cap is closed on the radiator neck. Any pressure build-up will go to the expansion tank where liquid and gas will separate, and excess gas will be pushed out. Test to be done with engine fully warmed up.

Good luck and please keep us posted!