Blown GT6 head gasket or...

[SveinHa]

My GT6 Mk3 with Mk1 engine is loosing quite a bit of water thru the expansion tank. I can drive 20-30 km and it starts to run hot. Sounds like a blown head gasket but I'm wondering if it is likely to be a problem that all external hoses except to and from the radiator is removed. The heater and the pipe running thru the inlet manifold is missing.

Anyone with a qualified guess about the missing hoses, can they compromise water circulation in some way making the engine run hot and spit out the water ?

[nang]

Wouldn't think so. Suggest a compression test before you take the lid off. Maybe check that thermostat is working too. Take it out, hang it in a cup of boiling water and see if it opens.
Tony.

[SveinHa]

Thermostat is brand new and compression is 11.0-12.2 bar.

[GT6 M]

have a good loook at the sealing rubbers on the cap.
there 2, one below t,other.  If the lower one is no seating right, then it lets water thru,
Before its got to  the pressure needed.

I actually had this last week, but a slightly diff scenario,  water had  been threw oot the expansion bottle.
so checked that , and what it was was a bit of silicon gasket, prob frae the water pump, had some how come loose, and just a fluke when I put cap back on after a top up, it caught the silicon, and trapped it on the seal.

it were enouugh to let water past, so give symtom of loosing water by internal compression.
So have a deek at the lower rubber.

M

[SveinHa]

The cap seems old but the rubber is ok. It had a slight grove due to the static pressure from the spring so I turned the rubber upside down. New cap is on the list for my next order from Rimmer og whoever...

Some additional info. Compression is as follows:
1: 12.0 bar
2: 12.2 bar
3: 11.5 bar
4: 11.0 bar
5: 11.5 bar
6: 12.0 bar

I have noted that cylinder 4 and 6 is running 30-40°C colder than the rest by measuring the exhaust manifold with an IR thermometer. All sparkplugs look equal suggesting no water is entering the cylinders.

Neither the previous owner nor I have any experience on this engine but it it supposed to be newly rebuildt. I got the GT6 late i January and have done LOTS of work to get it ready for MOT. Anyone fancy reading Norwegian, the work done is documented here: http://www.sveinha.com/j16/index.php/bil/triumph-gt6-mk3/gt6-arbeidsblogg

[Richard B]

Get a pressure tester (about £50) over here.

Hook it up to the radiator and handpump the water system.

If the pressure drops you have a leak...  

Just used one on my Stag  :'(


ps you can have the head crack tested, seeing as its a cast iron head.

pps as it's a MkI engine, the studs are not very strong, you did torque to 46lbft not 65lbft

see Chris Witor's website for fitting MkII cylinder head nuts & studs.

[Sheepy]

You can get a head gasket tester kit, I have one but may be a wee bit far for you to use it! ;)

It's basically a special blue liquid (can't remember the name off top of my head) and you place some in the tester pippett bottle, hold it over the expansion or radiator cap, and suck up some of the air, if the liquid turns green the head gasket has gone! Showing there are hydrocarbons in the water.

Most good garages should have them! It's quick and easy to use.

[SveinHa]

Thanks Sheepy.

I don't find that kit in my local partshops but I guess my local garage can help. I'll ask them to check when I take the GT6 to MOT test in a few days.

[SveinHa]

Have been thinking quite a bit about my coolingproblem. Since the car still haven't got MOT (hopefully tomorrow, only minor problems left), I haven't been driving too much but if the head gasket is blown and some water is blown out to the overflow bottle, will all of it be sucked in again when the engine cools down, I don't think so? Anyway it does so instead of changing the head gasket, I did some more thinking. No bubbles in the radiator...

Did a testdrive today with the electric radiator fan running all the time and no cooling problem  8) Seems like an airflow problem or dirty radiator (looks fine on the outside so some radflush may be useful).

[Richard B]

If the head gasket has gone I would look for white smoke in the exhaust or drops of water there.

[Pete Lewis]

if there are some blocked rad tubes the tend to block at the top , this seals the tube which is filled with trapped air, as the rad heats the air expands and the water is displaced

wise notes about head torque and the need for high tensile nuts and washers to get the 46lbsft. deformed washers and stripped std nuts all let the clamp go. no water in oil but combustion gasses get into the water jacket.

the manifold and banjo and pipe to pump all form part of the bypass system for when the thermostat is closed, so without this you could have local overheating in the head or be unable to displace air locks when re -filling the system

just some thoughts

Peter

[Richard B]

Oh a MkI engine, I forgot that, another can of worms entirely.

Canleys sell HD nuts which will torque to 45lb/ft.

nb. the ones they sell are a 14mm AF not a 9/16" AF, but the correct thread.

or see my previous post regarding MkII studs/bolts.

[tiggrr1]

peterhlewis wrote:

if there are some blocked rad tubes the tend to block at the top , this seals the tube which is filled with trapped air, as the rad heats the air expands and the water is displaced

I think that is what was happening to my GT6 which was displaying symptoms the same as SveinHa has been decribing in this thread.

A radiator change sorted it out for me, or be it a bit over the top it will leave a bit of room to tune the engine up a bit.

http://www.club.triumph.org.uk/cgi-bin/forum10/Blah.pl?m-1367750163/

[SveinHa]

I understand that the original rad is a bit on the small side for the GT6 so a change for something larger may be wise anyway.

Got MOT today so I went on the road for a small hour with stable temperature all the time with rad fan hotwired to run continously. Next step is to clean the cooling system and maybe also check the water pump.

[Paudman]

Richard_B wrote:

pps as it's a MkI engine, the studs are not very strong, you did torque to 46lbft not 65lbft

You've no idea how many I went through before realising the Haynes manual wasn't as clear as it could be.....  ;D

[Richard B]

Yes, I also got caught out by the Haynes "Book of lies".