Blown Head Gasket?

[Ian Vincent]

Having just returned from a month away, I decided to start my TR3a this morning.

 

First it was an absolute bu**er to start, it kept firing on one or two cylinders but wouldn't pick up but eventually I got it running smoothly and left it running on fast idle to warm up.

 

Normally it reaches operating temperature pretty quickly, almost too quickly in fact but I have recently reverted to an original four bladed water pump because I wasn't convinced that the impeller clearances were correct on the so called high performance item that was fitted previously, and that may have made a difference. Anyway, this morning the needle got to about 1/4 of the way along the temperature gauge and seemed to stop moving, then all of a sudden after about 5 minutes, it moved very quickly through the 185 Deg. F mark and was three quarters of the way to the RHS of the gauge (all without the electric fan cutting, which it normally does at about an indicated 190 Deg F), when there there was a rush of water and vapour from the radiator overflow pipe.

 

I stopped the engine and after a few minutes removed the radiator cap to find that the coolant level had dropped. I topped it up with about a pint of coolant and restarted the engine and the engine ticked over nicely while the temperature slowly climbed up to the half way point on the gauge and stabilised at about 185 to 190 Deg F.

 

So my question is, was it a large air lock or has the head gasket blown and is there an easy way to check without lifting the head?

 

Rgds Ian

[kob666e]

It sounds like an air lock, but how did it get there? Take it for a short run and see if it loses any more coolant. I was always told to feel the temperature of the rad, if it's vomiting out water and the top of the rad is hot but the bottom is cold then that's a sign of a blown head gasket, as the combustion pressurises the cooling system.

 

There is a test you can do to detect exhaust gases in the coolant.

 

Also what's coming out the back? Had a huge and sudden blown head gasket in a Peugeot years ago and couldn't see anything behind me for smoke and steam!!

 

There are different symptoms depending on where the gasket let go.

 

Best of luck.......

[harlequin]

'I have recently reverted to an original four bladed water pump' is most likely to the source of the air lock, as Justin suggests drive it locally and check for symptoms

 

George

[Geko]

'I have recently reverted to an original four bladed water pump'... I think it is possible to fit the thermostat the wrong way round...

[Stevecross]

Ian

Doesn't sound like a head gasket but as Justin says there is an easy test.

Your local friendly garage will have one. (most call it a sniffer)

Some most likely will have a more modern type I suppose but mine consists of a clear tube and a chemical indicator fluid, usually blue.

It works by "sniffing" the gasses present in the cooling system.

If the fluid turns yellow it is an indication that combustion gasses are present. That usually means a gasket problem but could also indicate a cracked head or block. Takes a couple of minutes and should only cost a couple of pounds (depending on the garage I suppose!)

Funnily enough, a friend of mine popped over this morning thinking he may have a head gasket problem on his GT6. Unfortunately for him the test showed positive so that's another job for next weekend.

Steve

[Don H.]

Ian

Doesn't sound like a head gasket but as Justin says there is an easy test.

Your local friendly garage will have one. (most call it a sniffer)

Some most likely will have a more modern type I suppose but mine consists of a clear tube and a chemical indicator fluid, usually blue.

It works by "sniffing" the gasses present in the cooling system.

If the fluid turns yellow it is an indication that combustion gasses are present. That usually means a gasket problem but could also indicate a cracked head or block. Takes a couple of minutes and should only cost a couple of pounds (depending on the garage I suppose!)

Funnily enough, a friend of mine popped over this morning thinking he may have a head gasket problem on his GT6. Unfortunately for him the test showed positive so that's another job for next weekend.

Steve

 

The tests for combustion gases in the coolant system are pretty simple, and cheap. The principle is based on CO2 being a primary product of combustion, and that gas being weakly acidic when dissolved in water. The test measures pH, detecting that acidity.

http://www.uview.com/site/ywd_uview/assets/pdf/99081870_comb-leak.pdf

 

It's a fine idea to have a friendly shop run this on your car. I'm betting on a blockage or air lock in the cooling system after the water pump change.

[Lebro]

Thermostat stuck shut ?

 

Bob.

[Peter Cobbold]

Thermostat stuck shut ?

 

Bob.

+1. Try running with it removed.