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Overflow bottle overflowing, while thermostat housing dry. In GT6 MK1 original euro setup.

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RolandB Avatar
RolandB Roland Beernink
Eindhoven, NB, Netherlands   NLD
Overflow bottle overflowing, while thermostat housing dry. In GT6 MK1 original euro setup.

I have done some basic maintenance since I got the car (2 years now) . new brake lines , pads, fluids, new oils. Replaced all rubber radiator tubing, Flushed and put new coolant in the system , new thermostat.
Before I start a drive I make sure the overflow bottle is halve full.
And while driving I keep an halve eye on the temp gauge. Always just before halve.. and while standing still or a longer drive. It’s at halve, or just over it. (Full gauge reads nicely from empty to full).

I notice when I stop the car after 30 minutes. To 60 minutes’ drive. The bottle is always completely full. And overflowing because its wet around the bottle. (I even saw small bubbles coming from the tube today)
It even happened a view times (like today) that while driving I see water droplets rolling over the bonnet.. Looking under the bonnet its completely wet coolant has been pushed out of the bottle by force it seems. (underside bonnet completely wet)
I stopped for an hour and i removed the filler cap and filled the system again with +/- 200cl water/coolant (I keep a bottle in the car and can re-use water from the overflow bottle, making sure the end of the tube is fully submerged).

I drive home from there (30 minutes). i let it cool off a few minutes while measuring some temperatures with a IR/laser thingy.
Thermostat housing .. 90 C degrees (194 F)
Radiator housing .. 76 C degrees. (168 F)
Cylinder head between plugs.. 73..78 C degrees. (163 .. 172 F)
Inlet manifold (water tube) between.. 63.. 90 C degrees… (145 .. 194 F)

After measuring, I very carefully removed the radiator filler cap (expecting pressure, and maybe even steam).. but I think I felt some slight under pressure..
and it looked empty again. I also removed the thermostat housing, only a few droplets…. And the thermostat is fully open at that time I removed it with a rag being still pretty hot. And put it in some colder water , it closed nicely.
How can I trust a temp gauge If the sensor is in an empty housing?

I refilled the system with +/- 100cl I see the level of the radiator and thermostat housing rise at the same time! (they seems to be ‘communicating’ which is ok I think).
I have putt a pulley to a drill and I see water coming out of the thermostat housing.. (at least the pump is doing something).

Anybody has any idea of what is going on… is there some kind of blockage in the system?
Why is the system not pulling back water from the bottle, but pulling air in somewhere..
Did I not fill the system correctly?
Wrong type of radiator cap?
Any ideas are welcome!

(Sorry, English is not my native language i might have typed stupid things.).
Roland

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spitfire50 Avatar
spitfire50 Paul Mugford
Rochester, N.H., USA   USA
Roland,
The first thing I would suspect in your case is indeed a bad radiator cap. The cap must not only seal pressure in, it must also allow the coolant to return when the system cools. The hose between the radiator filler neck and the overflow bottle must also be airtight. If that hose leaks the vacuum in the radiator will only draw air in when the coolant cools. Since radiator caps are relatively inexpensive a new one might be worth trying. Some repair garages have a tester to check the pressure relief valve in the radiator cap, but I don't know if the vacuum return valve can also be tested.
Best of luck,
Paul

JFB Joseph Byrd
Dunn, North Carolina, USA   USA
expanding on what Paul stated....ALL parts of the coolant must be air tight so that when the coolant cools, it draws from the bottle and not air.

the thermostat being above the radiator cap can cause a wierd observation. as when the radiator cap comes off, the coolant level can rise, drain into the bottle and leave the thermostat dry.

Suggest this method to try to remove ALL air from the coolant system. with the radiator cap off, run the engine and make it get hot so the thermostat opens and you see coolant flowing in the top of the radiator. slowly and completely fill the radiator till coolant drains to the bottle. One now ASSUMES the top hose was full and no air when the radiator cap is put back on. with the car hot, fill the bottle. Let the car cool down and see that the bottle levels drop

the amount of coolant expansion detremines how much the bottle should hold. I just know the thermal expansion of water is 0.042 times the coolant system fill capacity from cold to hot. Now this amount of expansion will be less is the ambient temperture is warmer.

Is the bottle volume large enough?

if the bottle vloume is too small, of course it will overflow when the car warms up, BUT worse will be that it will suck the bottle dry when it cools

I marked up a radiator cap illustration just for discussion. and repeating Paul's statement. the top cap seal MUST be perfect.

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Lizzard d id
san jose, ca, USA   USA
Maybe take it to a shop that has a "sniffer" , then ask them to sniff the radiator . If there is exhaust in the radiator then you need a head gasket .

another way is to test the fluid itself

Tonyfixit Avatar
Tonyfixit Tony M
Duncan, British Columbia, Canada   CAN
I was thinking Head gasket also.

gfe05111952 Avatar
gfe05111952 George Earwaker
Falls Church, Virginia, USA   USA
Roland, I had a similar problem with my 1968 Spitfire a few years ago. As others have said, the overflow/recovery system must be airtight. I replaced the usual suspects: radiator cap & overflow hose. This didn't help. I took the radiator to a shop specializing in radiator repair. After relating my problem, the specialist looked at the area where the cap attaches (blue arrow) and noticed an irregularity that was preventing the cap from making an airtight seal. They replaced that part, fixing the problem. Another area where you may have an air leak is where the overflow exits the radiator (red arrow). That part is subjected to a lot of pulling, pushing and wiggling up and down as owners pull off and push on the overflow hose. I have had air leaks occur where it attaches to the radiator. All it takes is a pin hole to allow air to be drawn back into the radiator instead of coolant from the overflow reservoir. I hope this is helpful.



George
1967 Triumph GT6
1967 Triumph Spitfire4 Mk2
1968 Triumph Spitfire Mk3


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Manana Avatar
Manana Steve Wten
Thornhill, Ontario, Canada   CAN
All awesome points guys.

The only elaboration I'll make, although super-obvious to those with experience, but for any novice reading this thread.... The only part that is NOT air tight is the overflow bottle, fluid needs to go in an out of there with no resistance. The hose just needs to go to the bottom of the bottle so it can extract fluid as the system cools.



Steve
http://stevew10.wix.com/spit16

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mykeeb33 Avatar
mykeeb33 Silver Member Mike Bostwick
Puyallup, Washington, USA   USA
Not sure it matters , but is the radiator cap pressure correct?.... 7 or 13 lbs.

JFB Joseph Byrd
Dunn, North Carolina, USA   USA
for my education...

Is the radiator cap LOWER then the thermostat?

I found the coolant capacity as 4.5 l, thus the maximun thermal expansion volume in and out of the bottle would be 190ml. If you are blowing out more than that, the mentioned head gasket.

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RolandB Avatar
RolandB Roland Beernink
Eindhoven, NB, Netherlands   NLD
Thank you all for the good advice,

As I know I had low compression on cylinder 2 and 3 , and with minimal difference when putting I bit of oil in the cylinder, i wanted to remove the head and inspect valves and head gasket any way.
But I wanted to postpone this as the next winter project. Not realising this could also be the cause for the coolant problem.

By reading the posts, I pulled the project forward. (I have a spare engine block and head In unknown state KC400. So I spend my time yesterday removing the head and carefully drilling out a broking stud.
This morning at 8:00 I will be dropping it off, to get it cleaned at flatten the surface.
Hoping to get it back soon, is my vacation with this car starts at the end of next week….. (Or I have to go with the Volvo…).

As I side note, the radiator cap, was already a new one LBS 7 is I think is the correct one…. Replaced it for this problem already.
The length of the tube to the bottle. It just correct, to the bottom of the bottle.(not flat. So it could pull vacuum on the bottom. With a slight curve.)

I also tried to search for the coolant check set. But that seemed quite expensive (88,- euros). Could have been nice to confirm the head gasket problem.. but as it seems logical it’s the head gasket.. I didn’t want to delay).

Again thank you all ! I will post an update, with what I find. And the results…

Roland

scardini1 Avatar
scardini1 Gold Member Jim Moscardini
Great Mills, MD, USA   USA
1968 Triumph GT6 "Rocinante"
2003 Jaguar XKR "Kitty"
Hi Roland,

I had the exact same problem when I put my car on the road 2 years ago. What I found was the radiator cap specified by all the FLAPS was too short. See the pictures. The distance from the inside of the cap to the seal surface, was almost exactly the same distance as the depth of the well in the radiator. So regardless of whether it was a 7 or 13 lb cap, because the spring wasn't getting compressed at all, hot coolant and/or steam would just easily slip by the cap and into the reservoir. I went to the parts store and made them show me other caps (regardless of what car they for) until I found one that would fit and that was just a little longer. Everything has been fine since. No overflows. Not even when the Temp Gauge is right at the red-line (205 degrees F on my car).


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Lizzard d id
san jose, ca, USA   USA
In reply to # 1463498 by RolandB Hoping to get it back soon, is my vacation with this car starts at the end of next week….. (Or I have to go with the Volvo…).
Where to ? Will there be photos ? Can I go along as a riding mechanic ? What kind of Volvo ? An "Amazon" ?

RolandB Avatar
RolandB Roland Beernink
Eindhoven, NB, Netherlands   NLD
Hello Jim,

That’s sounds interesting, i will double check that. And compare it with the old cap (which had the same problem, but that had worn-out seals..).
But wouldn’t it pull back the water from the bottle when cooling as long as the highest seal is still air-thigh


Lizzard , Sorry only 2 seats available, One seat for the beautiful girl. And I am supposed to be the tech support….
But If the GT6 fails and we have to go with the Modern 2014 Volvo V40 then there are 2 extra seats if you like to go on Holiday From the Netherlands to England for 2 weeks..


Roland

scardini1 Avatar
scardini1 Gold Member Jim Moscardini
Great Mills, MD, USA   USA
1968 Triumph GT6 "Rocinante"
2003 Jaguar XKR "Kitty"
Hi Roland,

The spring and internal seal don't even need to make contact within the well for reverse flow to occur as the engine cools. All that's necessary is that the cap itself is sealed to the lip of the well. With my spring and internal seal only slightly compressed (as in: "barely"winking smiley, it yielded to pressure that was much less than 13psi when the engine was running.

Take a look at my pics again. It's possible that the seal wasn't even in contact with the bottom of the well. And remember: I also had a stock GT6 MK1 radiator and tried two different radiator caps, from two different sources (Spitbits and a FLAPS) that were BOTH listed for the GT6 MK1. The MK2/3 cap had the higher pressure rating, but it had the exact same dimensions.

Lizzard d id
san jose, ca, USA   USA
In reply to # 1463568 by RolandB Lizzard , Sorry only 2 seats available, One seat for the beautiful girl. And I am supposed to be the tech support….
But If the GT6 fails and we have to go with the Modern 2014 Volvo V40 then there are 2 extra seats if you like to go on Holiday From the Netherlands to England for 2 weeks..
I'm already sitting in the back of the GT6 . A tour of England in a GT6 !!!
Can we go to mouse hole ?
https://www.google.com/search?q=mousehole+england&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjXl4W1obnUAhUL8GMKHS__BMMQ_AUICygC&biw=1600&bih=794

And then you should maybe take the head off the motor that is in the car now and get it reworked at the same time as the other one , that way you will know its one that fits and works with the engine in the car now . It would be less that fun to find out the other head doesn't fit / work when time is running out .



Edited 1 time(s). Last edit at 2017-06-12 04:45 PM by Lizzard.

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