Hi,
My 88 is at my mechanic’s getting the clutch done (5spd conversion). It belched a half a litre of coolant from front of engine overnight while up on hoist. He is thinking water pump, but hasn't investigated yet. Just looking for any general thoughts from anyone who has had a water pump go on a V12. Hoses done fairly recently and water pump done 40k km ago, so no obvs reasons spring to mind........bit like the clutch which only has 10k km on it
It did this weird thing a few weeks back. Driving in traffic and coolant temp fine. Parked it for 5 mins (20 deg C outside). When I went to restart it kept stalling and needed lots of gas. Temp was up to 3/4 on gauge........ heat sink? I turned on twin auxiliary fans and drove it home and temp gauge fine. I then parked it in storage for a couple of weeks and it did lose a half lite of coolant from front of engine. Thought it was AC water from my LR4 which I also parked in same spot. Now I am wondering if the leak is related to the heat sink episode and trying to dispel any contemplation of head gasket issues (its at 150k km). Or the heat sink episode related to leak? It has evans waterless coolant if that matters any.

It has had a new radiator fairly recently (previous owner) and generally has had a lot of TLC from previous owner (i have owned it for 2 months).

My mechanic noted that it was typical behavior for a cat in marking its territory by spraying. Humour not appreciated! I can't work on it now that its stored for winter, so will have to rely on mechanic to sort it out.

Any thoughts based on personal experience very welcome!

 

Check out the three rubber hoses that connect the crossover pipe to the two thermostat housings and water pump. Those are often skipped when the hoses are done on the V12. All the small bleed hoses can dump a surprisingly large amount of coolant in a short time as well.

The stalling on hot starts could be vapor lock from high fuel temps (heat soak) on the fuel rail. When you give it lots of gas it clears the vaporized fuel from the rail. If this is happening regularly it's a sign you're running too hot.

It's common for the V12 to heat soak after shutdown, and it's a very dangerous time for dropped valve seats. You park the car and everything is fine, then come back and hear the clatter of death on start up. I have witnessed heat soak temps as high as "top of the N" on warm days, which drops after the engine is running again. 3/4 up the gauge is Danger Zone. It should NEVER be that high under normal operation. Before I overhauled my cooling system I used the crack the bonnet after parking on hot days. When in doubt, go around the engine with an infrared thermometer. Make sure both water rails are similar temps, check incoming and outgoing temps from the radiator, cylinder heads, and might as well hit all hoses with the thermometer.

It sounds like you have two problems which may or may not be related. 1) Your engine is getting too hot on shutdown 2) It's dumping coolant after shutdown. The leak could be a separate issue, or the coolant could be coming out the cap (or someplace else) if the system is over-pressurized.

 

Hey, thanks for your thoughtful reply.
yes I wondered if the stalling issue after heat soak might be fuel vaporization.
I have driven it half a dozen times since buying it but always parked it back at the underground parking spot which I park it in over the winter (rented). So that was the first time I let it sit and then drove it again. When returning it to its parking spot I put the dust cover back on (parking spot 20 mins from my house) and was worried about that hindering cooling further - valid concern it seems.
It has the auxiliary fans and will use those more diligently going forward after determining if there are any issues that require fixing re. Cooling system. The manual fans can stay on after engine turned off obvs, but I wonder how effective they are if coolant not circulating?
good tip re. IR thermometer!

 

So thinking about this some more.
What doesn't make sense to me is why the temp gauge went so high after I turned the engine off. The concept of heat sink I get, but once coolant is no longer circulating (engine off) the heat sink characteristics of an engine with pristine cooling system or neglected cooling system should be identical? I wonder whether temp gauge is reliable? (Assuming it is until I know otherwise)

 

The heat sink will be the same if the system is full. It sounds like you have a leak somewhere and if coolant is getting out air may be getting in, assuming it wasn't just overfilled to begin with. Its possible for an air bubble to have formed around the coolant temperature sensor and that hot air is what you see when you start the car. Then once the coolant starts circulating the gauge drops because the coolant is cooler than the air. I would get the cooling system sorted and then deal with the heat soak.

 

The temp gauges on these cars will reliably show an increase or decrease in coolant temperature. However, it is impossible to know actual coolant temperature from the gauge reading alone. First off, obviously, there are no numbers. Secondly, there is no consistancy. The "middle of the N" might be 180º on one car and 200º on the next. That's why so many use a hand held infra-red thermometer to get some sense of the temps really are.

Cheers
DD

 

Better than nothing.

Some very diligent owners will shut the engine off, let the aux fan do its thing for a couple minutes, then briefly restart the engine to circulate the coolant a bit. And perhaps repeat a couple times.

You'd never catch me going thru this routine. But I'm not diligent

Cheers
DD

 

Your mechanic will almost certainly do a pressure test which will pinpoint the source of the leak.....although sometimes the source is obvious on simple visual inspection.

Sadly, the quality of replacement parts has been getting iffy over the years so seemingly low mileage/time since xxx-parts were replaced really can't be relied upon to eliminate them as possible faults.

With any luck your leak is just a hose failure. Or maybe even a loose hose clamp. Water pump replacement on these cars is not a minor thing.


Starting and running issues due to fuel vaporization are indeed "a thing" on these cars. Higher coolant temp = higher engine bay temp = hotter fuel rails = greater chance of fuel vaporizing.

But there are others possible problems that might cause similar symptoms to fuel vaporization.

All you can do is repair what obviously needs repairing (cooling system in this case) and then see how things shake out.




Well, when dealing with 34 year old cars, espeically something like a V12 Jag, a sense of humor .....or philosophic attitude, at least.....can be helpful

Cheers
DD

 

Yes, Doug is 100% right, a pressure test is called for and will show up the leak for certain.

 

My mechanic said the same thing re. Replaced parts can fail prematurely.

It has evans waterless coolant. Thinking of ditching that as I don't want to ever be in a situation where I need an emergency top up and have none available. Any general thoughts on pros/ cons of waterless coolants?

As ever, big thank you for everyone's thoughtful responses!

 

My limited research on waterless coolants has shown that opinions and experiences are all over the board.

I'll stick with the coventional old fashioned coolant. I'll admit, though, to having become a bit jaded about the real-world benefits of specialty products.....especially in cars that clearly don't require them.

Let's hear what others have to say.

Cheers
DD

 

Concensus on past posts here re. Evans and topic investigated by living with a classic on youtube is that due to poorer heat conductivity, engines run a bit hotter on Evans. Living with a classic also noted increased heat soak and higher gauge Temps after parking and restarting. He then switched back to reg coolant.
Thats good enough for me! Will be ditching the Evans and will revert to ethylene glycol / water mix.

 

Quick update:
turns out the coolant loss was due to several hose clamps needing tightening. Guess they were not retightened after hoses were last replaced. Also, one lower hard to get at hose had no clamps fitted!