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TR7 V8 Air lock?


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Hi All,

 

I am at my whits end here, looks like I have an air lock. Symptoms are, after having the motor out last year, on start up she will warm up normal to 1/4 and then quickly heat up to 3/4 before falling back. repeat this until stat opens and she runs normal from then on. I have changed the stat, dropped the water out (not the block as the drain plug is solid). Run her with the bead hose off. Filled from bleed hose and top hose. No change. Only time she will run normal is with the stat out. I ran her for most of last year with the stat out. Trouble is with the cold now she runs well below 1/4 so put stat back in and back jumping about.

 

 

Am i missing something?
Edited by maddog
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Hi there,

 

I don't profess to being any expert but I had EXACLTLY the same problem as you.

 

I took the advice of Robsport and filled the system as normal. I then got a 2 litre empty plastic drinks bottle, cut the end off it and wrapped the pouring end with insulation tape so that I created a 'seal' between the bottle and the header tank. I think filled this 1/2 full and got someone to increase engine revs - this sucked more water into the system. With the revs still increased I put the cap back on the resevoir and I have been running perfectly since.

 

It didn's suck much extra coolant into the system but it has certainly solved the problem.

 

I hops this helps and if so please post a reply here - I believe this is a fairly common problem with the TR8.

 

Thanks

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Hi Andy,

 

expansion tank mounting might be the problem, it may need relocating to ensure it is above the level of the uppermost hose ?

 

Filling the system with the expansion tank unmounted and held up higher whilst filling through it might also solve the problem.

 

Cheers,

 

Alec

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Hi,

 

I drilled a couple of extra hole in the thermostat, about 1/8", this will allow trapped air out. Also when first filling jack the front of the car up and fill allowing the coolant to run into the heater. Always pre-mix your coolant before filling as neat anti freeze can be viscous. Finaly on mine i installed a bleed point in the top hose to let me fill via the highest point ( thats not on the curve of the hose ) and also doubles as a point to let the air out, see picture below. When running her up gently squeeze the top hose so pump the air out and keep the heater on hot.

 

 

latestpics1091.jpg

 

 

Cheers John

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Hi Andy, Not sure that I'm convinced it's an air lock. I dont know the layout of your system but I can imagine a scenario where the engine starts to warm, thermostat opens, a slug of cold water enters the engine block, temp gauge goes down, thermostat closes, engine heats up, temp gauge goes up, thermostat opens, a slug of cold water enters the engine block............Of course that all depends on how fast your thermostat opens/closes where everything is etc.

 

Just a thought - probably worthless - Al

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Hi all,

Thanks for all the replys. Got out into the bleak mid winter over the weekend and tried again, dropped all the water out, lifed the car from the back before filling as you advised. Seemed to work alright with the extra tank/bottle fitted but after allowing to cool right down and starting her again no result, just the same upto 3/4 befor dropping back down and up as stat opens.

Had a eureka moment today at work (slow day) so bi-passed the heater and sorted. Turns out I have got the heater plumbed in back to front. Just took her up the road and it seems ok. Will give her a good run tomorrow.

Thanks again for all your advice.

Beers all round when I see you

Andy :rolleyes:

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I can't remember the full story, but there are some replacement water pumps in the market, which do not have the small bleed hole that feeds the thermostat drilled. This causes the problem you describe.

 

Further there are some water pump gaskets that either don't have that bleed hole, or can be installed the wrong way round, causing the same problem. As my son has my 8 12500Km away from here, & I don't expect it back anytime soon, I did not pay all that much attention when it was discussed on "The best Triumph TR7/8 forum on the net" a while ago.

 

I suggest you go there & use the search facility on the TR8 [or TR7 v8] forum. Be persistent, the search facility on that site is not the best on the net, & can take some convincing to liberate the required information. There are a number of photos of both pumps & the other problem gear, showing the cause of the problem very clearly.

 

 

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  • 1 year later...

Hi all,Thanks for all the replys. Got out into the bleak mid winter over the weekend and tried again, dropped all the water out, lifed the car from the back before filling as you advised. Seemed to work alright with the extra tank/bottle fitted but after allowing to cool right down and starting her again no result, just the same upto 3/4 befor dropping back down and up as stat opens.Had a eureka moment today at work (slow day) so bi-passed the heater and sorted. Turns out I have got the heater plumbed in back to front. Just took her up the road and it seems ok. Will give her a good run tomorrow.Thanks again for all your advice.Beers all round when I see youAndy :rolleyes:

Hi

So which way round do the hoses go?

Al

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