Overheating advice

[andyf]

This started last weekend on the way back from Retro Rides show. The gauge started reading slightly hotter than normal, then without warning shot up to 3/4. I pulled over and had lost a lot of coolant through the overflow. I topped the coolant back up, and got home (another 30ish miles) without incident, although the gauge was reading hotter than normal (slightly over 1/2 as opposed to the usual half way between 1/4 and 1/2).

This weekend I changed the thermostat (both are correct ones with foot) and also the radiator cap, topped up the coolant and went for a run. It ran for 20 minutes with no problem, I even let it idle for another 5 minutes and it was fine, with the electric fan cutting in as it should.

I then took it up the dual carriageway and had the same problem. It started to run hotter (just over 1/2), then suddenly shot up to 3/4. I pulled off the dual carriageway and the gauge immediately dropped to just over 1/2. I accelerated hard away from the junction and it jumped up to 3/4. I pulled over. I (very carefully!) removed the cap and had lost at least a couple of pints of coolant which I topped up. I got back home (about 10 miles) without further problems.

With the engine running I can see no signs of bubbles in the header tank, and I can see no signs of water in the oil.

Ideas please? (Sorry for the essay).


1980 Persian Aqua DHC

[Marsu]

I've had similar and then followed the ROM procedure to slacken and then re-torque the head.

This is a service item that should be done regularly.

[Rust Restorer]

Exact symptons I had, I suggest you get a garage to do a gas test on the coolant or buy one http://shop.ebay.co.uk/items/__cylinder ... 459_228460

Although I had no oil in water and vice versa the test identified presence of gas in water, later investigation showed gasket was blown between 2 cylinders.
By all means try Marsu's reply first.

Andy
1980 DHC Cashmere Gold
1981 FHC Persian Aqua Blue
www.andys-tr7.co.uk

http://andystr7blog.blogspot.com

[gaz]

i don't think i could offer more advice than you have got/will recieve off the forum other than check your rad isn't blocked are all your hoses getting hot etc. but.........
[:(]my sympathy is with you on this again good luck Andy........[:(]




It rides again..... and again wehey!!!!!!!

[richards]

Defiantly check the rad, might be worth removing it and back flushing to see if its full of crud, Make sure it still has most of its fins! Also, after filling it, unbolt the expansion tank and raise it up as high as you can with the engine running, this can help to eliminate air locks which can cause the same problem.

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[UKPhilTR7]

I would suggest also re-torquing the head to make sure. That is something that I have got to do very soon after the rebuild. Is there any signs of water leakage on to the block from the head?

Just out of interest at what reading on your temp gauge does your electric fan kick in? Mine is just over half which i think is a little too early.

[andyf]

The fan kicks in at a smidge over half, and the rad was new at the beginning of the year so all should be fine there. I don`t think an airlock is the problem because the engine has been running beautifully ever since about May when I put it back on the road. It went from Devon to Billing and back in a day without a problem, and the temperature gauge was rock steady. This only manifested itself the other weekend.

There is no sign of water leakage anywhere (well, except from the overflow obviously). Maybe a retorque is in order and hope for the best. I would count myself as bloody unlucky to have two head gaskets let go within a year, particularly after Richards generosity with the new engine, but I guess it looks like that is the probable cause.


1980 Persian Aqua DHC

[John Clancy]

This is showing definite evidence of head gasket failure but don't go down that route until it's the last resort. I expect you have electronic ignition which is a bit of a fly in the ointment for this but ensure the timing and everything else distributor related is correct. I overheated once and had all these symptoms because the distributor had shifted and put the timing way out. Dumped copious quantities of coolant out through the overflow but despite that the cylinder head and the gasket survived.

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[Beans]

<blockquote id="quote"><font size="1" face="Century Gothic, Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by UKPhilTR7</i>

... at what reading on your temp gauge does your electric fan kick in? Mine is just over half which i think is a little too early ... <hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">
In none of my TR7's the temparature gauge ever rises above the halfway mark.

As for the problem, indeed check all obvious things first (timing, and both fuel and coolant systems).
Never pressume something's OK, check it [;)]

And before you retorque the head I'd recommend a compression test.

B.t.w what coolant have you been using?

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1981 TR7 FHC Sprint (better known as 't Kreng)</font id="blue">
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[bmcecosse]

I can't see any point in re-torquing the head! If the gasket has been leaking - even slightly - it needs re-newing.

[Marsu]

The BL engineers specified in the ROM to "Check/adjust torque of cylinder head nuts/bolts" as a maintenance item to be performed every 1000 miles (1600 km).

Given the symptoms described do not indicate a failed head gasket (ie, boils soon after starting) it would seem prudent to perform this 20 minute task, rather than commencing a strip down.

I concur with Bean's suggestion to perform a compression test before re-torqing.

Andy, is this new engine? Was the head re-torqued after running in? Standard practice is to do this within the first 500 - 1000 miles.

[Gubi]

Been reading this thread with interest. In the Alfa world its common to retorque the head every now and again to prevent leaks, but in those engines it's fixed studs with nuts at the top (i.e., the studs never come out for head removal)

Given that I'm not sure the last time the head was touched on my seven, am I risking snapping/loosening a stud or something if I try a retorque at some point? Is it best to just leave things well enough alone?

-----
Tom
'79 TR7
'87 Alfa 75
'91 Alfa Spider

[John Clancy]

I just leave them Gubi. But I might change that if I ever start having head gasket problems. If it ain't broken, don't fix it works well for me right now and has done for 25 years.

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[richards]

<blockquote id="quote"><font size="1" face="Century Gothic, Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Marsu</i>


Andy, is this new engine? Was the head re-torqued after running in? Standard practice is to do this within the first 500 - 1000 miles.
<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">

This was my old engine, unless Andy has rebuilt it the engine has been running just fine for some time, I drove around on it for about 18months including some long trips (london to yorkshire and back) without any problems, it was sitting for about 10 months before Andy collected it but it was stored in my dry garage.
Still sounds to me like a blockage floating around the cooling system.

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[andyf]

Yep, Richards right. It was his old engine, and as he said it was running perfectly well, and using the old adage "if it aint broke, don`t fix it", I didn`t.

There was no way I was going to strip down and rebuild an engine that was running so well, particularly as a) The head is a pain to remove, and b) I`m too lazy.

It had a new radiator, thermostat & rad cap (obviously), a good clean externally and a flush through of the old coolant (which was still healthy looking), and obviously service items. I added new anti freeze, about 40% mixture roughly.

Timing was done only a few weeks ago but I will recheck it even though it appears to be running fine.


1980 Persian Aqua DHC