Foaming expansion tank at revs/ coolant overflow/ what tank do I have?

[fatallightning]

I've had an issue lately where with higher revs and longer WOT pulls, the expansion tank seems to foam/aerate to the point where it starts to push coolant past the cap. Once I use more sensible throttle the level settles back out. It seems to be aerating via the top bypass hose. I've tried repeated bleeds and burps. Rad did some have a small leak I had professionally repaired. I've taken some coolant out of the level to try and prevent this, picture show is level at full cold. I may just replace the header tank and cap just to be safe. Any ideas?

 

 

[ashyers]

I was having some weird cooling level issues that turned out to be the cap. The cap on your Birkin appears to be the same as the one on my Caterham. The two p/n's I found for a replacement were PCD100160 and GRC184. The cap I ended up with was an OEM Rover cap. I'd suggest you try that 1st as it's inexpensive and easy.

[panamericano]

Too long in isolation??? That tank looks like good legs and a cute butt to me.

 

Too full would have been my suggestion, but the photos do not look like it. However, if the temp gauge is not reading hot, maybe you shoule lower cold level at tank even more and think of it as an expansion tank. Changing cap, as suggested, is always a cheap try.

 

What does it do if you loosen cap (pressure)? How hot is it really running?

[Dave W]

You my be seeing cavitation at higher rev's. If the engine is not over heating, slow down the water pump speed.

Dave W

[Vovchandr]

You my be seeing cavitation at higher rev's. If the engine is not over heating, slow down the water pump speed.

Dave W

 

I'm having cooling woes myself and starting to think that cavitation is my problem. Original 19 year old Zetec water pump and it has plastic fins. Only thing I didn't change (and timing) during last tear down.

 

My coolant seems to never get rid of bubbles coming out and also dramatically expands once it gets hot and over flows out of cap.

 

I do suggest getting one of these , just don't buy the generic Amazon one or you'll have to make your own adapters like I did.

 

I had to butcher a spare cap and Dremel existing adapters to make it work. Not recommended

 

Edited July 22, 2020 by Vovchandr

[fatallightning]

I'm having cooling woes myself and starting to think that cavitation is my problem. Original 19 year old Zetec water pump and it has plastic fins. Only thing I didn't change (and timing) during last tear down.

 

My coolant seems to never get rid of bubbles coming out and also dramatically expands once it gets hot and over flows out of cap.

 

I do suggest getting one of these , just don't buy the generic Amazon one or you'll have to make your own adapters like I did.

 

I had to butcher a spare cap and Dremel existing adapters to make it work. Not recommended

 

 

that appears to be the same tank I have, any idea where it's sourced from?

[yellowss7]

It’s from a rover. Caterham used to stock them

[FE07]

Have had the exact same problem in the past with my Zetec powered SLR. High revs lead to bubbles into the overflow tank (same tank as depicted) and then overflow out with loss of coolant and overheating. Initially thought must be air in system. Bled everything-no air and same problem. Then began to note black slightly oily residue building up in the overflow tank. Given overheating and now what appeared to be exhaust fumes in the overflow, figured blown head gasket. Took the car to George Alderman who replaced head gasket and made some other 'while were in there' changes. Seemed to run fine for a while afterwards. Then back on track and same thing as described with high revs. Back to Aldermans. Both George and Paul seemed stumped as to whats up. They decide to look at how the cooling system was arranged on the Ford Contour/Focus and rearranged what was initially the stock plumbing on my car for a Rube Goldberg rearrangement of the plumbing. Also jumped the temp sensor which controls the radiator fan so it now runs constantly. When I picked it up- wasn't thrilled at what had been done but too late at that point. Car seems to run fine. No overheating or spitting out through the overflow tank however- I haven't tracked the car since the plumbing was changed. Bottom line- before I did ANY of that- I'd get a new overflow cap AND only run the car with enough antifreeze to just begin to show in the bottom of the overflow tank, not halfway up. It will still bubble into the overflow but wont leak or likely overheat.

 

I know you'll want to see how the plumbing was rearranged. Will try to get some pictures.

 

TurboTom lurking on here? Any thoughts?

 

Jim

[Vovchandr]

Have had the exact same problem in the past with my Zetec powered SLR. High revs lead to bubbles into..

Jim

 

Pretty much same problems as me to a T right now on my Zetec.

 

I thought had gasket for sure, gas escaping into coolant.

 

However did leak down test. Good. Then did the exhaust fumes in coolant test. Also good.

 

Engine is healthy.

 

A friend of mine is suggesting fitting a swirl pot as a solution instead of overflow. I'm hesitant but likely will try it.

 

I might try running less fluid and getting another cap ordered up.

 

The drastic expansion of the fluid while at temp and revving is puzzling

[papak]

Stock water pumps will almost assuredly cavitate at high rpm. All fixed pitch propellers are optimally effective in a fairly narrow rpm range. To deal with this, you can either run an electric coolant pump (Davies Craig or others) or plumb in a swirl pot to de-aerate the coolant before it continues through the system. The guys who run Evans NPG coolant are advised to reverse the coolant flow for best performance but this strategy really only works for NPG coolant due to it’s fluid properties. I have run the Evans stuff in a 944 at Willow Springs in the summer with no problem but most sanctioning bodies won’t allow it any longer. If you spill some on the track, it is REALLY greasy. I believe the Evans website has a couple of excellent technical articles on coolant plumbing.

[Croc]

that appears to be the same tank I have, any idea where it's sourced from?

 

Its off a Rover 200/400 up to 1995. The Rover was derived off a Honda in a pretty basic form of engineering, so there is a Honda part equivalent out there. The tall back leg is cut down to suit where mounted.

https://rimmerbros.com/Item--i-EAP8713

[coffee break]

Does the overflow tank need an overflow tank? :banghead:

[yellowss7]

Guys not to be a downer, but I chased bubbles at high revs pressurizing my coolant tank for a couple of years. Tried Evans coolant. Replaced water pump,radiator, installed one way valves and moved the headertank to the highest point. Tested for exhaust gases in the headertank. Negative I installed a higher pressure cap which worked a little better but I still got pressure build up at track revs.

 

After each track session I would winch my car up the trailer ramp to put the tank as the highest point. Bubbles would bleed up into the tank and the level in the tank would go back down to normal. It did appear that the higher pressure cap prevented it blowing out the cap. I would do that after every session and the car ran fine and did not overheat. BTW. I ditched the Evans and went to straight water with water wetter.

 

I had enough of this so I did an experiment to see at what revs the pressure built up. I ran successive session on track at fixed RPMs starting at 3000 and cranked it up 500 RPM in each following session. No bubbles/ pressurization at revs under 5000 rpm. At 5500 RPM. The pressurization and bubbles in the system showed up.

 

No loss of coolant. No gases in the tank. But after all the time, money on part replacements and huge denial. I finally pulled the head and replaced the head gasket. There was a small area that appeared to cause the issue. After reassembling, it runs great with no pressurization or bubbles in the system.

 

May have no bearing on your issues but just felt the need to share. Best of luck. Tom.

[Croc]

[Vovchandr]

Guys not to be a downer, but I chased bubbles at high revs pressurizing my coolant tank for a couple of years. Tried Evans coolant. Replaced water pump,radiator, installed one way valves and moved the headertank to the highest point. Tested for exhaust gases in the headertank. Negative I installed a higher pressure cap which worked a little better but I still got pressure build up at track revs.

 

After each track session I would winch my car up the trailer ramp to put the tank as the highest point. Bubbles would bleed up into the tank and the level in the tank would go back down to normal. It did appear that the higher pressure cap prevented it blowing out the cap. I would do that after every session and the car ran fine and did not overheat. BTW. I ditched the Evans and went to straight water with water wetter.

 

I had enough of this so I did an experiment to see at what revs the pressure built up. I ran successive session on track at fixed RPMs starting at 3000 and cranked it up 500 RPM in each following session. No bubbles/ pressurization at revs under 5000 rpm. At 5500 RPM. The pressurization and bubbles in the system showed up.

 

No loss of coolant. No gases in the tank. But after all the time, money on part replacements and huge denial. I finally pulled the head and replaced the head gasket. There was a small area that appeared to cause the issue. After reassembling, it runs great with no pressurization or bubbles in the system.

 

May have no bearing on your issues but just felt the need to share. Best of luck. Tom.

 

Thank you Tom. That is very constructive.

 

Luckily head gasket isn't too big of a job on a car like 7.

 

I wouldn't rule it out in my case at all as I know my engine got very hot quite a few times during troubleshooting my fan circuit/wiring after buying the car and ironing out the kinks. Not out of realm of possibility to have gone bad.