Overheating

PeterTR7V8 · Postby **PeterTR7V8** » 01 Feb 2009 08:50

The cooling system has two caps. 1 on the radiator & 1 on the header tank. The rad cap is rated for 15 pounds & I have no idea what the rating on the exp tank is but it has a valve in it that opens when jabbed with a screwdriver. The rad cap is quite new but it was pointed out to me today that the lip on the radiator neck that the rubber seal under the rad cap is very smooth so the cap probably isn't holding 15 lbs. Despite having a valve the plastic exp tank cap doesn't seem to release any pressure or allow for any expansion so when the car get hotter than usual it blows coolant out past the rad cap which makes the overheating worse. So I think what I need is to 1. fix the seal on the radiator neck & 2. find a cap for the expansion tank that does release presure.

I don't think I have a head gasket problem, at least there are no signs of oil & water mixing.

Had a great day at the hillclimb. The car ran great & apart from one very scary moment everything went according to plan. Check my blog for more.

************************************************************************
To do list:
Upholstery/Motor/Gearbox/Suspension/Brakes/Carb/Tyres../Gearbox/Paint/Cam+Motor
Done......./done./done....../done......../done../done/done/redone.../done/under way
Blog: http://www.forum.triumphtr7.com/topic.asp?TOPIC_ID=8548

Odd · Postby **Odd** » 01 Feb 2009 09:39

This I don't understand!? Why two pressure releasing caps?

You only need one pressure releasing cap - and that one should be fitted to the volume where fluid expansion is
taken care of. To the gas side of it of course! So, if your strange contraption of a cooling system have two caps
- see to it that the one directly on the radiator do not open at all, never, not at any pressure. Solder it shut if needed.
And then you see to it that the one on the expansion tank opens at the desired pressure (and not sooner, or later).
Then you're home free...

PeterTR7V8 · Postby **PeterTR7V8** » 01 Feb 2009 10:27

I don't understand it either. This is the way the car was when I bought it & it is only when things go wrong that I pay attention to them. You are right though & I should probably just lop the neck off the radiator & weld it shut. But before I do that I need to make sure the expansion tank cap is working otherwise I'll start blowing hoses.

This is only an issue when I'm doing track days.

************************************************************************
To do list:
Upholstery/Motor/Gearbox/Suspension/Brakes/Carb/Tyres../Gearbox/Paint/Cam+Motor
Done......./done./done....../done......../done../done/done/redone.../done/under way
Blog: http://www.forum.triumphtr7.com/topic.asp?TOPIC_ID=8548

PeterTR7V8 · Postby **PeterTR7V8** » 01 Feb 2009 10:33

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by tr8coupe

[:D]running to high temperatures results in 1 cracked blocks 2 slipped liners and 3 lower power [:p]<hr height="1" noshade id="quote"></blockquote id="quote">

True but what I found using the capilliary guage that showed me actual water temp was that the radiator cap was failing at about 110C which is not hot enough to cause damage to the motor. Because the in-dash temp guage showed 7/8s & water was blowing out of the radiator cap it looked like the overheating was worse than it was.

************************************************************************
To do list:
Upholstery/Motor/Gearbox/Suspension/Brakes/Carb/Tyres../Gearbox/Paint/Cam+Motor
Done......./done./done....../done......../done../done/done/redone.../done/under way
Blog: http://www.forum.triumphtr7.com/topic.asp?TOPIC_ID=8548

Odd · Postby **Odd** » 01 Feb 2009 12:49

<blockquote id="quote">quote:<hr height="1" noshade id="quote"> I should probably just lop the neck off the radiator & weld it shut. <hr height="1" noshade id="quote"></blockquote id="quote"> If you do, don't forget to make sure the top of the radiator tank can communicate with the
(higher up it seems in your picture) fluid phase of the expansion tank - or you'll build yourself
a trap for a gas bubble in the top of the radiator.

btw.
Personally I'd never dare operate my RV8 at the temperatures (110-115 Celsius!) you're mentioning.
My car is fitted out so that in the unlikely case it would pass beyond ~105 degrees Celsius the twin
electric fans kick into overdrive mode and a hurricane passes through the (heavy duty!) radiator.
This has never occured so far, ordinary calm operation of the fans in low speed is enough. And,
should I see an unexpected reason for hastily changing from high speed driving to commuter
congestion ahead - I can trigger a 3 minute manually invoked operation of said hurricane.
Overheating an alloy engine is expensive, so every measure to prevent it is encouraged... [:)]

tr8coupe · Postby **tr8coupe** » 01 Feb 2009 14:30

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by PeterTR7V8

[quote]Originally posted by tr8coupe

[:D]running to high temperatures results in 1 cracked blocks 2 slipped liners and 3 lower power [:p]<hr height="1" noshade id="quote"></blockquote id="quote">

True but what I found using the capilliary guage that showed me actual water temp was that the radiator cap was failing at about 110C which is not hot enough to cause damage to the motor. Because the in-dash temp guage showed 7/8s & water was blowing out of the radiator cap it looked like the overheating was worse than it was.

************************************************************************
To do list:
Upholstery/Motor/Gearbox/Suspension/Brakes/Carb/Tyres../Gearbox/Paint/Cam+Motor
Done......./done./done....../done......../done../done/done/redone.../done/under way
Blog: http://www.forum.triumphtr7.com/topic.asp?TOPIC_ID=8548

<hr height="1" noshade id="quote"></blockquote id="quote">

at the factory new blocks are heated to 140/145 degrees centigrade
then they cam out of the oven then the liners go in at room temperature so you guys figure out what temperature you should run the engine ??
the best engine buider in this world says at no more than 80 you should run the engine or damage might result in quiker than you think

and header tanks only add to the problem

BMW Z1 ( sold)
Westfield sport carbon (sold)
Eurosport x1/9 turbo (sold)
TR8 coupe
TR7 v8 monster on 245 tyres all round (sold)
TVR VIXEN

PeterTR7V8 · Postby **PeterTR7V8** » 01 Feb 2009 19:36

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Odd
If you do, don't forget to make sure the top of the radiator tank can communicate with the
(higher up it seems in your picture) fluid phase of the expansion tank - or you'll build yourself
a trap for a gas bubble in the top of the radiator.<hr height="1" noshade id="quote"></blockquote id="quote">

That's probably why the radiator cap was left on because the hose from the bottom of the expansion tank meets the radiator half way up. But in my earlier posts I described what happened when I connected the radiator overflow spout under the radiator cap to the expansion tank - ie the expansion tank cap wouldn't release the pressure.

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Personally I'd never dare operate my RV8 at the temperatures (110-115 Celsius!) you're mentioning.
My car is fitted out so that in the unlikely case it would pass beyond ~105 degrees Celsius the twin
electric fans kick into overdrive mode and a hurricane passes through the (heavy duty!) radiator.
This has never occured so far, ordinary calm operation of the fans in low speed is enough. And,
should I see an unexpected reason for hastily changing from high speed driving to commuter
congestion ahead - I can trigger a 3 minute manually invoked operation of said hurricane.
Overheating an alloy engine is expensive, so every measure to prevent it is encouraged... [:)]
<hr height="1" noshade id="quote"></blockquote id="quote">

Agreed which is why I started looking into it. The problem with having a normal Cold/Normal/Hot temp guage is that you don't know the actual temperature or whether the sender is correctly tuned to the gauge especially with a conversion job like mine. This is why I put the capilliary guage in. Usually the motor runs at about 88C or less & only gets to 115C after a serious beating. The new fan certainly seems to help & the motor ran cool all throughout Sunday's hillclimb with short beatings of about 1 minute followed by a lot of idling so I won't really know until the next track day cos that's the only time it overheats.

My fan kicks in before 90C & I have a big radiator too. So what it all boils (ha ha) down to I need to get the expansion tank cap sorted so it blows off pressure before the radiator cap.

************************************************************************
To do list:
Upholstery/Motor/Gearbox/Suspension/Brakes/Carb/Tyres../Gearbox/Paint/Cam+Motor
Done......./done./done....../done......../done../done/done/redone.../done/under way
Blog: http://www.forum.triumphtr7.com/topic.asp?TOPIC_ID=8548

tr8coupe · Postby **tr8coupe** » 01 Feb 2009 22:11

[:D]and some other guys apply same rules as an iron block on the rover v8 ally block all those rulles must change other wise severe problems might arise from it lol[:D]

BMW Z1 ( sold)
Westfield sport carbon (sold)
Eurosport x1/9 turbo (sold)
TR8 coupe
TR7 v8 monster on 245 tyres all round (sold)
TVR VIXEN

Cobber · Postby **Cobber** » 02 Feb 2009 09:12

My old Jaguar XJ12 had two caps on the cooling system one on the header tank and one on the (higher) on the engine pipe.
The engine pipe cap had no pressure relief it was just a sealed cap, the one on the header tank was of the normal pressure relief type.
To fill and bleed the system you had to remove both caps ane undo the bleed screw on the radiator, fill until all the air is expelled from the radiator then close bleed screw, then continue to fill until all air is expelled from header tank, then fit cap to header tank and contine filling till full.
So with that process in mind I wouldn't be in any hurry to solder up the cap on the radiator as you will need to bleed the air out!
I don't however see a need for two pressure relief caps but if they are both relive at much the same pressure I don't see any harm in it.


80'Triumph TR7, , 73'Land Rover (Ford 351. V8),
'89 Ford Fairlane
85'Alfa 90, 69'Ford F250.
76' Ford F100

Anonymous

Overheating

Who is online