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Coolant Over Pressurising


Henry Boler
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Hi All,

 

I know this is kinda similar to another thread on the go at the moment but I didn't want to hijack it so here goes...

 

I have a problem with my cooling system at the moment, it wont keep the water in!

 

This problem annoyed me enough to rebuild it all the last few days. So as far as I'm aware there are no leaks, there are also no blockages and it's all lovely and clean inside, always has been, which I guess would make it obvious if there were any contaminants getting into the coolant.

 

What happens is I start with an empty system, I fill it up, fire the engine up run it for a few seconds which blows the trapped air out, I then top up with water and pop the cap on. Then from cold I go for a drive, within a minute I've got interior heating working just fine as you'd expect, I warm her up a bit more then as she gets hotter the heating fails, i.e. air in the matrix and then gradually everything comes out through the pin hole in the top of the expansion bottle at a very high rate, I then switch off and watch the expansion bottle sit there bubbling...

 

I am stuck for ideas, I've tried everything I can think of, is there anything I might have missed? Or am I getting the fill procedure wrong? I've done this for years, my spitfire never had a problem, this GT6 has never been as easy to fill but I've never had this much grief...

 

Henry

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Sounds like an airlock to me, fill the system really slowly letting air escape as the water displaces it, then with the rad cap off run the engine until no more air bubbles are seen. Can be worth getting the front of the car higher so it encourages the air to vent and possibly loosening the top hose replacing it once water is running freely.

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That's what my initial thoughts were/still are sort of...

 

I ran the engine and kept filling it up until air stopped coming out, then I left it and did the process again and again. To be fair I did get more out every time. I drove her to work today 10 miles, and there were bubbles coming out again, but the heating remained on. When shes cool I'll see if there is room for more water. The water is definitely running as there is a massive water jet from the hose that enters halfway down the filler neck.

 

I'll keep you posted!

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make sure the thremostat has a jiggle pin in the rim to let air out when filling if missing drill a 3mm hole in the support rim .

 

as GT6 has a low level filler below the top hose always best  refill with engine idleing  ,heater open and if poss get front of car up  much higher than the tail

 

 

just some thoughts 

 

Pete

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Hi Henry,

I had a similar problem on a non Triumph and it was caused by a failing hose (the inlet hose into the pump in this case) collapsing at higher revs, thus blocking the flow of water. All seemed fine idling on the drive.  

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Are there any give aways that this could be head gasket related? Would there be any smells or colours in the coolant?

 

The car has always made a few bubbles from the overflow, it's never caused me a problem and I do long journeys no problem, I have tried very hard to stop the bubble in the past, instead I have a sight glass halfway down the hose that shows me that it is still drawing water back in after a run.

 

When my old spitfire bubbled it meant it wanted a new head gasket within about 50 miles but the GT6 has done a good 10,000 miles this year with no problems at all.

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I thought when I read your first post, head gasket. :(  You say you have no visible signs of leaks but are you loosing any water? That would indicate head gasket.

 

Interior heating within a minute sounds a bit soon. What does the temperature gauge say? My GT6 need at least 5 or 6 miles to get to normal operating temperature.

 

Is your thermostat working? Take it out and boil it up in a pan. Try running without a thermostat what happens?  Might give you some more clues.

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Try running the car from cold with the rad cap off, see what happens. If the HG has gone, I would expect to see bubbles and the water getting hot/overflowing pretty fast. In a normal car it should tick over happily for quite a while without getting too hot, 5 mins at least.

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I'm not sure if I'm losing water or not at the moment. I'll chech in a few minutes when the system has cooled and is below atmospheric pressure.

 

I checked the heating on the way home from work, 2 minutes from startup and there is warm air coming out of the vents, the temperature gauge still reading cold at this point. I'd say that was a good sign of a functioning system. Still taking 5-6 miles to get to operating temp as you say.

 

Yes thermostat is fine, I boiled a pan of 5 of them together on the hob this Sunday and they all functioned in the same way at the same time...

 

I will try running the car tomorrow morning with the cap off from cold. I have done it for a little while whilst I was topping up the system and there was no sign of air coming out or any water being forced out either...

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Update, I couldn't get the cap off it's still got loads of pressure in it which is unusual for my car at the moment... And nothing but a bit of water came out when I turned the cap so thats a good sign I guess as well. I'm off to southampton for dinner now, 15+ miles each way, I'll let you all know how she goes later!

 

I had a load of old spitfire ones I found! So I thought whilst I was at it I'd see if any or all worked!

 

It's funny as all this started on the way home from my local ish meet in Petersfield, the Southern club! Actually rather a long way for me, almost an hours drive each way, but I like driving so that's fine!

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That sounds like a plan. How safe is it to do that? Is there any chance of damaging the fire rings or anything?

 

I seem to recall doing it on my spitfire years ago not long after a gasket change and it then blew, but that might just have been the unlucky spitfire engine that didn't like head gaskets...

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Will do. I think you might be on to something there anyway as I ran it this morning for 5 mins with the cap off and every 10-15 seconds there was a small cluster of bubbles coming up, and the water level never went down at all which I guess if it was air locks escaping it would do...

 

Just a quick question, I'm sure the answer is yes, but does the rocker shaft have to come off for this?

 

I'll tighten them up tonight when I get home.

 

Henry

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Okay, so I got home, backed all the nuts off and re torqued one by one. Then topped up the system and ran the engine with the cap off, bubbles came out and then I think they stopped. Went for a really quick drive round the block and there was air in the overflow pipe but it wasn't bubbling. So I let it cool down and have topped it up again and removed all the air in the overflow pipe and the cap so it will be obvious if there is any new air in there. Gonna drive down the motorway soon and see what happens.

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Thermostats that have been cooked dont always work well after a good boiling

 

if youre getting localised boil causing air to expand and push out a good volume of water theres

realy only 3 likely ...air lock due to a filling problem or partial blockage or the gaskets letting combustion pressures into the jacket, or radiator tubes blocked at the top, these trap air which expands when heated and the change in volume pushes out coolant

with your continuing bubbles its looking more like gasket

 

just some ideas

 

pete

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I think the thermostat is fine as the car maintains normal operating temperature, also I can see when it opens as I get a visible water jet coming in half way down the filler neck.
 
Radiator wise, how would I know if the tubes are blocked? I've cleaned the radiator out very thoroughly numerous times over the last few years and it has always cooled very efficiently.
 
Head Gasket I hope isn't the problem but who knows... The thing is all this only started when I decided to flush the cooling system the other day... Which implies something related to that has changed to cause the problem but I don't know...
 
Last night after my post from Southampton, I just decided to get in the car and just drive it home it was fine, heating was back on and all... This morning is worked fine as well but was bubbling when I got to work. It seems that driving hard down a motorway, even for a short run like today which was about half a mile on the motorway gets the system bubbling... Head Gasket?
 
Stupid Car!!

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you could make sure the flushing hasnt moved some crud to block the tube under the manifold and its union in the back of the pump  

these have been known to clog, and the bypass doesnt work .

 

if you get bubbles ? when under pressure of loaded faster drives then gasket is still up in the top culprits

 

 

as for the rad , not easy , do the tubes you can see in the header look clear,  the tubes often get sort of capped ,and quite visible

 

doing a flow test needs 2 gallon at a good 15ft head and a 2" pipe to feed the rad then time how long it takes to empty a known amount

without any spec. its not going to prove much. 

a garden hose job is a waste of time  just not enough volume /flow .

 

if the rad is blocked it will have cold zones in its centre ,(as it cant get hot water down a blocked tube  but how to tell as the rad is there to cool hot water 

so if hot at top and cold at bottom its deemed to be working ...

my views would follow  .. the .what have I done last syndrome, has this caused a blockage  somewhere ( cheap to check out.before you use more £££ and labour of love )

 

head off and change the gasket

 

rad off to a repairer to check the tubes 

 

so its running the correct temp.,  its making bubbles,  the re is air is changing the coolant volume and blowing out as if overfilled 

 

 

, the stats tested , and  by now any air lock should have cleared   

 

 

a compression test may give  some clues but compression pressures  chirruping through the fire rings into the water jacket doesnt always show much loss on a test

 

keep at it all will be revealed ........

 

Pete

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"this only started when I decided to flush the cooling system the other day"

 

There's a clue! :lol:

 

Generally it's the last improvement you make caused the problem.

 

How did you flush the engine? just top and bottom radiator hose? If that's it youmay just have pushed all the sludge into one place causing a more effective blockage.

 

Or did you take out the engine drain plug, carb side near/below number 6? Some people even take out the core plugs. Sometimes you have to poke out the drain plug with a wire coat hanger!

 

Here's an interesting video, can't understand a word he says and I don't think it's a Triumph 2litre engine but this is how to do it.

 

https://www.youtube.com/watch?v=JllvVHKo07U

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