My guess is you're experiencing the thermostat to the coolant in the engine block opening, then closing back.

 

Thanks for the feedback. I think what's odd is that if the thermostat opens up you would think it would just draw more coolant in and not push it back into the expansion tank. So I have it full and I'm getting heat so I know the thermostat is opening up. So far no leaks. I'm essentially read to start road testing it but I have another question for the group here.

How do you know for sure that I have all the air bubbles/pockets sorted out. How can I tell if I've bled the system enough or properly? Or is there now way to know for sure? One thing I'm also a little concerned about that I mentioned earlier is what if the system is overpressureized or possibly overfull?? Could that do damage, blow a seal, gasket etc... I actually have the expansion tank only about half full right now since I'm concerned about it pushing more coolant back into it at some point??

 

Hi @Trainingdragon

For the underlined part above - Just the opposite. There is already coolant in the engine behind the tstat. That water is hotter then the water on the other side of the tstat. When the temp of the coolant in the engine is too hot for the tstat to hold, it opens and that hot water (which is expanding) pushes out, then the cooler water backfills that gap. And, I think that is the "push/pull" oscillation you're seeing in the reserve tank.

If the system is full to the required mark, the system should be taking in more and more new coolant just oscillating.

If the tstat is good, there should be no overpressurizing. Even if the tstat goes bad and stays closed you would get an overheat message. As long as you respond to the message, you should not do damage.

On air in the system, do you not have a bleed screw on the highest coolant pipe? I did on my F-Pace (albeit the V6). This bleed screw is on the pipe going to the heater core. With the system up to operating temp, opening that screw slightly so you see coolant dribble out usually has the air in the system that escapes first. My refill and startup after the pipe replacements went without a hitch. I've hears some say they needed to open/close the bleed screw a couple of times.

 

Thanks Dionysus that's helpful to know. So brings up a couple of more questions then. Can you operate the bleed screen (on the expansion tank for me V8) while the coolant is hot - is it safe to do so?? And, if the systems seems to be filled properly, can you explain why at different times the system pushes coolant back into the "fill bucket" that I put on top of the expansion tank only for fill and burp purposes. Ive seen that bucket almost fill to the top, then when I shut down the car, it pulls it all back in. My concern is that once I put the cap on and seal the system, what if it needs to push that coolant back out and theres no where to go with it. Will it break a seal somewhere?? Right now I believe the system is burped and the expansion tank cold is a little under full but not low in the thank. I'm still concerned that last time when I had it this way, maybe the system was actually too full and needed to find a place to get rid of coolant so maybe blew a seal or gasket somewhere??? So last question, if there is too much pressure, do you know if there is a part of the system that properly relieves pressure?

Sorry for all the questions but I"m really trying to do this right and not have to take it all apart again

 

Hi @Trainingdragon

To answer this Q, YES, there is a pressure relief for the system. It is the fill cap to the tank. All of these caps will have the max pressure before the cap releases the "air" that is in the space of the tank between the max fill line and the top of the tank (in this case 200kPa), and why you don't want to fill the tank past full as then if pressure needs to release, it will be liquid and not air. On the bleed screw, you only need to open it part way, not take it all the way out as it is slotted so air starts to escape before liquid does (when liquid appears to be bubbling around the screw the it is bled). Hope this helps.

 

Thanks yes that's helpful. So the cap will release pressure before a seal will blow (hopefully). So any thought why the system will push so much coolant back into the fill bucket at times (used while filling and bleeding only)? Is it because the cap wasn't on or possibly something else?

 

One more thing about these pressure relief caps. They are matched to the system requirements so if ever replaced, they should remain the same kPa

In this pic, the yellow caps is from my F-Pace V6. The red one from my Aston DB11 V12; the white one was a cap I replaced years ago, I believe from either on of my XJs or maybe my XK8

 

Coolant is circulating through the system via a water pump. When the tstat opens, it pushes the hotter coolant out of the engine block and into the system. With your fill bucket attached the coolant doesn't stay under pressure, instead finds the easiest passage with is the fill bucket. With the cap in place (system capped off and system pressure allowed to build), the coolant level in the fill tank and the gap above the max fill line allows these coolant surges to occur under the allowable pressure. When a void exists in the system bc of the surge it creates a vacuum there and when things normalize the gap is filled with the same fluid that surged earlier.

 

Hmm interesting. It makes sense and I'll have to think about that a little more so thanks for the explanation. I think the part that I might be having some trouble with is that the system is filled to the max line when cold, draws in coolant when the engine starts so lowers the level in the expansion tank, when needed, it will push coolant back into the expansion tank and probably shouldn't go over the max line if filled properly. There's only a small space between max line and top of expansion tank. My bucket filled almost to the top (maybe 20+ ounces) which seems like a lot of coolant to push into that bucket if the system was filled correctly. Unless what you are saying is that the cap keeps pressure so the coolant pushes through the system instead of overfilling the expansion tank while running. Sorry for all the questions but I'm trying to wrap my head around how this operates to see if I've done it correctly.

 

Thank you @Dionysus for the complete explanations and watchpoints.



That said, all the cars I have ever owned (including the two mid-engined ones, with the engine at the back and the radiator at the front, and coolant lines that run low on the floor) will purge air within 5 - 10 drive cycles. It helps to remove air if you hold the RPMs a bit high (say, 4000 RPM) for a continuous minute or two, for the next couple drives.

The F-Type's header tank / reservoir where the '200 KPA radiator cap' is, is the highest point. You can either remove the cap (cold) to monitor the coolant, or look carefully at the front side of the reservoir.

Our bleeder looks like the one you pictured in post 383, but it is black plastic. IMO no need to fuss with it.

 

Thanks Carbuff2. That makes some sense as well that I just need to drive the car around to circulate the system. But, question, are you suggesting that I drive with the cap off to allow air bubbles out or, drive it with the cap on and then re-bleed the system after a few drive cycles??

 

NO. Leave the cap properly in place.

Just monitor the cold coolant level, top off if needed...but do not overfill, that will just waste coolant.

 

got it. Thanks. So is there any sure way to know if I've gotten all of the air bubbles out? I.e. properly burped the system? Or just assume that if it doesn't get hotter than normal it should be fine?

 

I will say: PROBABLY

That is because modern cars have 'dampened' temperature indicators, that typically stay in one indicated place until the engine overheats, and blows up...



An OBD reader would probably display accurate coolant temps...but then you will risk the battery discharge if the Hazard triangle doesn't extinguish after 10 minutes. <<sigh>>

Best, just to monitor cold coolant level over the next few drives!
You should be checking all the underhood fluids periodically, anyway.

 

ahh thanks. I didn't realize that the temp indicator/gauge may not provide real time data. I thought it would. And as far as the fluids go, there's really not a lot to check. No power steering pump and oil is checked by the dash instead of a dipstick. So for the moment I'm running the cold coolant level a small bit below the min level line to ensure it doesn't overflow at some point. I'm wondering if I may have had it overfilled before leading to the significant leak under the supercharger but still very hard to tell what really leaked. I'll watch it after each short drive and see if the level stays stable when it cools down. If so, I'll top it off up to the min level and go from there. That's my plan at least for the moment.

 

So a little update. I drove the car around for a little while yesterday and all seems good so far LOL. Interesting though and maybe somebody might be able to explain this. When the car was cold, I checked the coolant level and it was at the same level after a good drive cycle and cool down cycle. Since I left the level a little low (expansion tank half full), I opened the cap to add a little more. When I did I heard a pressure release and a bunch of coolant got sucked into the system lowering the level in the expansion tank. Before I fill it up, I was wondering if that same coolant will push back and I run the risk of overfilling it. ????

 

I hope you're back in business by now🤞. its a good (and bad feeling sometimes) working on our own cars haahaa. Far from a master mechanic but with google/youtube and this forum our capability is increased by a lot👍. My f type is back up and running! Got the new wheels and big brakes on..last thing will be to tint the windows 😎. Fun ride..wish they made the v8 with a manual but I think the vap stage 2 tune can keep me content for a little while..just love the looks of em.

 

Wow that's a nice ride and I'm glad you got it back and hopefully everything is ok and no issues moving forward. At least since you had a shop do it you can go back to them if you have issues. The big brakes look great. While I'm not a big fan of black wheels, these look good.

Mine is up and running but I only have limited confidence so for now I only drive it locally where if there's an issue I"m not far from home. I have vehicles so I'm good not making this my daily. So far so good though. Fingers crossed. I'm actually and have been thinking of selling and moving on to another car. I've had this for about 5+ years now and have enjoyed it but I have my eye on so many cars and can't have too many at one time. I may be putting mine up on BAT in the near future after I give a some really good drives to ensure it's good to go.

 

Car looks fantastic! @Ksducati

While wheel choices are always controversial, (kinda like Boxers or briefs...haha), I happen to be on the "like" side of black wheels. In fact, I just changed the wheels on my Aston DB11 to black last month, as I did on my Bentley, my AMG and my C6 Corvette.

 

I was very hesitant on the black wheels..didn't know so many were against them now and that they aren't as "cool" as they once were🤣. I'll tint the windows this week sometime and that should help with the theme.. just didn't want anything too flashy but thank you!

I hear ya on the desire for something new-cars usually only last a few years for myself as well. Garage spots are limited and in order to put something else inside one has to go👍 anxious to hear what you go for on your next ride-if you remember please let me know. Always curious to hear what folks go for from one ride to the next.
Kevin