Scary experience yesterday coming back from the Laguna Seca Rolex Monterey Motorsports Reunion races. First the car started dragging with brakes causing me to stop. Solved that by disconnecting the vacuum reservoir and plugging the manifold hose that was now open. There must be a small leak in the brake servo to reaction valve causing the booster to apply some braking. That’s not the worst…
A few miles later the car temp started to rise from its usual “L” in NORMAL towards H. No good. Stopped when it was kissing the H and notices a little steam coming from the radiator cap hose, meaning its at 13#. Had to shut it down 3X for 2 hours each before limping back home. The last times the car seems to go from a lower water temp to close to H very quickly, say 2-4 miles. It’s as if water cooling was progressively being shut down or constricted.
The total water lost was only a few cups, so i know the engine never got overheated since I shut it down and allowed it to cool. This morning it started fine. No issues.
The car has a electric fan & aluminum radiator that was working. Water pump also seems pretty new (recently rebuilt) and spinning. No leaks.
I figure it’s either the water pump or one or both thermostats. It could be a plugged radiator but this car has been restored recently and the radiator has only a few thousand miles.
So:
Full coolant, no leaks
Radiator fans working
Water pump belts working and spinning the pump.
I did find the top of the thermostat housing significantly hotter than the radiator - as if the coolant is just not flowing.
Any insight or comments welcome.
So can a water pump spin, not leak but actually not pump much at all? It seems almost new but I thought I’d ask. How can I check is a water pump actually works? Is there a procedure to follow?
It the thermostats are closed, I think that would do it. I am ordering new thermostats. How likely is this? One or both would have had to fail progressively while I was driving…
It seems like the thermostats are the right first step. Since you have to drain the system, you may want to do a flush at the same time. With the V12, it’s possible for the left thermostat to be stuck completely closed, and you would still have the appearance of moderate temperatures, because the sensor is on the right. You’d still get a bare minimum amount of cooling, because the two flow paths are interconnected through the bypass.
Thanks for the comments. I just ordered “fail safe” 180F thermostats from Moss. They are more expensive but have this comforting statement:
“Give yourself some inexpensive insurance against overheating. Manufactured from high-grade stainless steel and copper, this thermostat locks open during overheating for added safety.”
I am a little skeptical: this feature locks open when it’s hot, but isn’t it something every thermostat does? The real question is what happens when the thermostat fails. Apparently this one cannot fail closed?
Does anybody have insight or experience with failsafe thermostats?
Standard thermostats have the ability to lock in the closed position, and while they don’t fail often, that seems to be their favorite mode of failure.
I don’t know much about the mechanics of the Fail-Safe style, but the theory is that they spring open when they fail, preventing a Chernobyl Syndrome.
Thanks for the insight. That sounds much better than the fail-close design. i guess it’s more expensive to do?
One last question before I remove the old thermostats (and test them - i want to be sure) is why not just leave them out? Since the car is garaged and in California without real winters, is there any drawbacks except for longer warmup periods? Will the engine not run as well running colder?
SV!
I would certainly replace both thermostats with NO Fail
thermostats, whether you need them or not.
Figure the Radiator can’t be to blocked up already.
Fail Safe thermostats give you no extra protection. They fail by default any time the engine is hot, so you’ll have to replace them if you overheat for any reason. If they end up failing closed, which they can, they won’t reopen for you. The base thermostats are also not the best. You’re much better off just going to the parts store and getting a pair of Gates 33188S thermostats. The Gates Superstat uses a weir gate design that gives better flow control at low temperatures, it’s actually a useful feature, not a gimmick. More importantly, it’s going to close the bypass correctly, which the Fail Safe won’t. I did exhaustive research on this last year, but it would seem to have gone for naught:
Great writeup Frank. I appreciate the information. i would have gone for the Gates or Stant Superstat part if I had not already ordered these first units. They are currently unavailable in the Bay Area for 1-2 weeks as far as I can tell so I’ll order a pair & extra gaskets for a changeout at a future time. I am hoping to get this cat up and running by this weekend. Hopefully this is what the issue was.
After taking the thermostats out and testing them, I found that both seem to work well. At about 180F, they both opened. Hmmm…can thermostats get stuck closed but somehow work when taken out and tested? I’ll assume not.
Uh oh…no smoking gun here. Well my current plan is to stick new (tested) thermostats and flush & put new coolant in the car. I hope it tests OK but frankly, that means I have done little.
Could the water pump belts be loose and slip at higher RPMs? Just wondering what else can do this…
I’ll look at the belts more carefully but running out of ideas. May I will buy new belts and install, maybe after tightening the current ones to see if things go back to normal? How hard is it to tighten or change the water pump-related belts?
After this, i could check timing to make sure it’s not really off but that seems unlikely.