That old overheating problem...

[jpyke]

I'm feeling rather depressed!

Had my new toy for just under 1 week now and it's just overheated for the second time. The first time was on the day I got it - I was very nervous when driving it home when I discovered that the temperature gauge did not work. Needless to say it dumped all its coolant out by the side of the road. Luckily I'd broken down outside a pub and the landlady was very kind and gave me plenty of water to top up and I got home with no problems. The first thing I did was fix the temp gauge and been watching it like a hawk ever since. Today I noticed it start to climb above half way so stopped in a hurry, waited a while, then emptied 2 litres of water into the cooling system and proceeded back home with the gauge staying put on normal.

Car is a 1972 MK1 Triumph V8 manual. According to the service history the engine was rebuilt not so long ago and has only covered 50,000 miles in total.

I have several thoughts on what it could be:

1. The dreaded head gasket(s). On sunday I did a compression test and got the following results (8.5, 9.5, 8.25, 9.0, 9.0, 8.3, 8.75, 9.0). I'm no expert but I thought these seemed good - would these be more variable if the head gasket(s) have gone?

2. I have a MK1 radiator but it has a blanking cap and the MK2 expansion bottle. Both caps seem very old and tired. They may need replacing - should I use a 20psi cap on the expansion? I'm guessing right now its the 13psi from the radiator...

3. There is no bleed in the pipe to the top of the radiator (obviously Mk2 radiators had a brass filler cap but this does not). There will definitely be a large air lock here.

Obviously despite my suspicions I want to make very sure that I have eliminated all other possibilities before I look at taking the heads off. I think I'll start by fitting a header tank near the fuse box as per many folks's recommendations. Again, should I go for the 20psi or 13psi cap?

I should note that all hoses seem fairly recent, no visible leaks. I think coolant is being lost by being pushed out of the expansion bottle and I need to work out why.

Any comments ideas would be gratefully received!

[Guest]

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Hiya, I think you've got it sussed, you want a 20lb rad cap, theoretically you can run with the lower pressure one, but they don't seem to cut it. Try the higher pressure cap before spending time and money, and stick a catch bottle under the overflow to see if that's where the loss is coming from. One prob with old cars is that people muck about with them,with no thought for consequences, a Mk2 rad is a priority. I wouldn't bother with a header tank till you've sorted out the loss. Your compression figures sound OK. Broke down outside a pub, how lucky is that ! Martin. P.S. got a name and location ?

[Ian Durrant]

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Hi jpyke,

If you are losing water rapidly via the expansion bottle its almost certainly not due to the rating of the pressure cap unless its really well pst its best. However overheating in itself can cause water to be pushed out due to the fact that the water is boiling.

What you need to ascertain is whether water is forced out through the expansion tank *before* the water boils or after.

Overheating is just as often caused by silted up radiators as blown gaskets, in fact I think most would agree that blown gaskets are more often the result of silted up cooling systems causing overheating than overheating is caused by coolant loss due to a blown headgasket. Something has to come first and since you don't know the history of you car (being new to you) I wouldn't despair yet. Look for other symptoms first. Do you have water in the oil or oil in the water (droplets of water on the dipstick for the former, a yellowish emusliion on the oil filler cap for the latter), either is a a pretty good sign of gasket failure.

make sure you have *absolutely no coolant leaks* a drop of just a few inches in the level of coolant in the rad will cause the engine to overheat due to the high mounted water pump. I once had an engine that overheated and required regulat topping up because one of the heater hoses was leaking and running down behind the bulkhead insulation making it very difficult to spot.

There are chemical tests for gasket failure that can be done that will diagnose a slightly faulty headgasket, theres history of discussion of this type of thing on this forum, a product called headchek, i believe.

Other symptoms of gasket failure can include steam coming from the tailpipes (but only after the engine and exhaust are hot, stags tend to emit steam from condensation when cold more than other cars for some reason).

If you don't have any of the major symptoms of gasket failure, then flush your cooling system throughly (plenty of posts on here about that!) maybe get your rad checked by a specialist. If you still can't cure the overheating maybe you have a gasket problem).

Theres a stack of experience from the owners on this forum on cooling system problems. Others will think of more to say on the subject. But as I say don't despair yet.

However if you do have blon headgaskets you must ascertain whats wroong with the cooling system tht caused this in the first place, or you will simply blow a new set.

Hope this helps and I know others will impart more information and things to look for.

Ian

[Guest]

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Ian Durrant wrote:

Hi jpyke,

If you are losing water rapidly via the expansion bottle its almost certainly not due to the rating of the pressure cap unless its really well pst its best. However overheating in itself can cause water to be pushed out due to the fact that the water is boiling.


Ian

Simple things first ! and stop scaring the guy, we want him to keep his Stag ! Martin.

[Ian Durrant]

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And I thought I was tying to show him that it could be something simple and not HGF, I still think its not going to be the rating of the cap, though a dodgy cap gasket could cause the problem, true.

[whereufromnosecity]

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Maybe worth checking the seal between the metalneck of the expansionbottle and the plastic bottle its self, it seems to be a weak spot in the design

(i have a good spare expansion bottle that you can have if you want to give it a try)

Stu E

[colin hanney]

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HI JPYKE, i had the same problem with mine when we got our car this year,the rad cap was 13lb,should have been 20lb.Then found it still leaked past the cap seal,it was a poor seal on the old overflow bottle.I fitted two seals with good old super glue and bob's your uncle ,so far so good.The seal is very thin so cannot press into the worn area so doubled the thickness.Hope this helps.colin.

[Stagdad]

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If you have a Mk 2 inlet manifold make sure you have the thermostat with a foot on the end of it to blank off the bypass.If you have a Mk 1 manifold it should look like the one in this thread and won't need the foot.

http://stagownersclub.mywowbb.com/vi...inlet+manifold

Cheers Steve

[kstar]

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In the mean time ensure you check the coolant is full every time you go out - hopefully it's not dropping too much in a day.

[Arbman Al]

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On a mk2 rad, when you undo the brass bung on the top with a cold engine, should the water level be at the top?

[redstag]

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arbman101 wrote:

On a mk2 rad, when you undo the brass bung on the top with a cold engine, should the water level be at the top?

Yes, it should be full to the top.



Pete

[Arbman Al]

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Cheers Pete.:dude:

Nice colour car BTW

[jpyke]

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Thanks for all the responses everyone! It has overheated twice since and on both occasions needed a fair amount of water. I've checked all the hoses are tight and I really don't think the caps are gone. I'm not going to use the car again until I've done some thorough diagnosis. I was thinking of getting an uprated radiator and fitting a header expansion tank so will also check the thermostat. I'm inclined toward head gasket failure... a gentle amount of steam wisps continuously from the exhausts and its not just the damp weather.

[StagnJag]

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Try this stuff, it will tell you if you have exhaust gasses in your cooling system. You would know for sure if it was HGF then.

http://auto.frost.co.uk/search?w=block+tester

Rgds

Dave

[V Mad]

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jpyke wrote:

..............and proceeded back home with the gauge staying put on normal.
Thats suggests the cooling system is working when full

I have several thoughts on what it could be:

1. The dreaded head gasket(s). On sunday I did a compression test and got the following results (8.5, 9.5, 8.25, 9.0, 9.0, 8.3, 8.75, 9.0). I'm no expert but I thought these seemed good - would these be more variable if the head gasket(s) have gone? Sometimes not always

2. I have a MK1 radiator but it has a blanking cap and the MK2 expansion bottle. Both caps seem very old and tired. They may need replacing - should I use a 20psi cap on the expansion? I'm guessing right now its the 13psi from the radiator... 20 psi should be OK

3. There is no bleed in the pipe to the top of the radiator (obviously Mk2 radiators had a brass filler cap but this does not). There will definitely be a large air lock here. I dont understand? What connect to the expansion bottle?

Obviously despite my suspicions I want to make very sure that I have eliminated all other possibilities before I look at taking the heads off. I think I'll start by fitting a header tank near the fuse box as per many folks's recommendations. Again, should I go for the 20psi or 13psi cap? I would advise that you sort out your rad/expansion question first. You may need to fit a Mk2 rad.

I should note that all hoses seem fairly recent, no visible leaks. I think coolant is being lost by being pushed out of the expansion bottle and I need to work out why.

Any comments ideas would be gratefully received!

Also try cranking with all plugs out: if it spits water from one cylinder then its head gasket time