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Triumph TR6 - TR6 burping coolant

When I park my TR6 (generally downhill on my street) the car begins to burp some coolant out of the overflow and on to the ground. The car is a '75 with a '73 engine. I did open the cooling system to change some faulty hoses and the coolant that came out was a dark brown, almost sludge! Time for a flush! The wierd thing is that before I opened the system, this problem never occurred. The car has a 7lb pressure cap on it now and when I change all the hoses out, I am switching it to the 13lb cap I bought. One other question, what is the best mthod of flushing this system and what would be the best type of flush product to use? Since I have many old Mercedes-Benzes, I have a jar of their citric acid flush which seems to work well in the MB systems. Would this be ok for the TR?

I guess I should have the radiator rodded and cleaned huh?

Probably a new water pump and t-stat will be in order. Again, since I am partial to German cars and their high quality German replacement parts, I am going to put in a Wahler t-stat. They are OE for Mercedes.

Any thoughts?


Drain and refill a couple of times, then add the citric flush. Get that "sludge" out of there! I've heard that after the citric flush, drain & refill twice, then add 2 tbs. baking soda to neutralize what's left. Then refill with distilled water & antifreeze. If you still have problems, THEN consider the radiator boil-out, new waterpump, ect.
Brent B

Hi Aaron

Your interior heater valve was closed when you topped up the coolant after servicing?

Almost always the reason. Air in interior heater core. Disturbed sludge may also create problem?

When fairly cool take off cap pull on the heat make sure valve opens. Let circulate till temp opens and fill as required.

Unless you are having other cooling problems don't change the rad cap value or acid wash. Just do, or have done better yet a simple reverse flush and fill. Cheap. Let them take care of the mess.

Don't know how long you have had car but some of the new cat dog friendly coolant is now brown in color. No sludge though :)

Sorry to disagree but "some" German car parts are crap, very very exspensive crap. Same as "some", Japan, American whatever. Lots of advertising.

When your parts are 3 to 25 times more expensive you should have a bit of longevity and quality built in? Nope reality is they try. All of them. But I have yet to meet an engineer with a crystal ball for the future or a corporation that was willing to admit easily, they screwed up.

Sort of like my car is safer ads. The only difference between a Mercedi's, Volvo and my old GM truck, getting swatted into a wall by an 18 wheeler is funeral arrangements. Due to my exploding gas tanks, my survivors have no choices and low costs? Gotta love corporate America always thinking of the rednecks :)

Dollar for Dollar you can't beat a middle aged American 1/2 ton for durability and parts price.

Sorry for rant and strong opinions

Bill Brayford

As a past owner/operator of a garage and radiator shop I would like to pass on a little info. Radiator flush solutions are crap. They are money makers for companies that thrive on our ignorance. If you are really going to put that acid in your cooling system, be prepared to replace core plugs shortly thereafter. If you have already put it in, dump in some baking soda to neutralize it. Then do a thorough flush with clean water. The back flush is a good idea. I like that part about letting them take care of the mess.
Joe Justice
Joe Justice

Citric acid isn't that bad - it's great for removing rust deposits. Probably 20-30 minutes circulating hot, then drain, flush, neutralize. It shouldn't go after "base" metal to any extent. Never use stronger acids.

The bad part is that a really plugged system will have extensive deposits, and corrosion goes on between the metal and the deposit mass - but the deposit acts as a plug. When the deposit is cleaned away - yep, you guessed it - that's when a hole that shows up.
Brent B


German cars/parts are expensive yes but I highly value them for their build quality. I've seen far too many old Mercedes come into the shop with well over 1/2 million miles on them (original block and heads) and are still using no oil.

I don't think nearly as high of BMW or Audi but MB will always be my first marque of choice.

I'm afraid to take the TR6 on any extended trips but don't ever give it a second thought driving a Mercedes of equal or even older vintage.

Anyhow, thanks to all of you guys for the comments. I hope to be able to get this cooling system issue straightened out before the brunt of summer hits us.


Citric acid is a weak, harmless (=Vitamin C) organic acid, but possibly ineffective at dissolving iron oxide.

Phosphoric acid is better for preparing rusty panels for painting. It dissolves iron oxide quicker than non rusty iron, and leaves a tough coating of iron phosphate. Even better, it is available in quantity for pennies as "Milk Stone Remover" from farmers suppliers. Your friendly dairy farmer uses it to wash out his milking machines - it is also used in many other food products, notably Coke! ( I don't drink the stuff; may change my mind about milk!)

But after cleaning a panel with H3PO4, the steel must dry and then be painted. My question, to any chemists here, is "Will phosphoric acid have a similar cleaning and protecting effect, inside the cooling system where it cannot dry?"


When you dry out the the steel panel a layer of iron phosphate forms on it. The stuff is nearly insoluble in water, and that film provided a removable layer of oxidation protection. Don't expect similar protection in an aqueous system. Also, at higher temperatures phosphoric acid will go after base metal - I wouldn't flush MY system with that.

Citric acid and glycolic acid are commonly used to remove rust from systems because both chealate the rust and get it in solution, but don't attack "good" metal. These are very common commercial cleaners.

Vitamin C = ascorbic acid.
Brent B

Hi Aaron,

Yes and No Don Elliot who must be off on another 7000 mile journey with his TR3 we havn't heard from him for awhile would beg to differ on TR reliable.

Bosch plugs are great and they look good. Have never seen a perfomance increase though. There deisel fuel injection pumps get around 125k out of there suggested 400K. Local rebuilders love them. Dealers say it is because people use non authorized fuel additives? And the fuel here is of inferior quality? Gas company says there full of SH**.

Rebuilder says they used junk seals in the first place? After rebuild they are still going strong up at 350k after repop?

So who do I believe?

If you want to go on a fast freeway trip across America. MB or any of the big 3 are a great choice. I like Buicks or Olds myself. Dealer serviced. Get you there boring and on time. Comfort at its best. Worry about the meeting whatever instead of the car.

Now a nice summer tour winding roads top down. No hurry or deadlines unless you feel like running hard just from exuberence. Reasonable distances each day. Thinking a bit about your CAR how she sounds how she feels. OOps thats not right. Pull over to the side of the road and adjust a bit. Meet 4 nice folks who were concerned. No problem you have just about everything short of a total rebuild in the boot. Eh Charlie? :)

Thats what the TRS were designed for. Nope its not a Continent Autobahn freeway car. It can be with some respect. It was designed for an island with limited distances and small fun roads. And in good tune just makes a great day.


Bill Brayford


I absolutely agree about the wind-in-the-hair fun that a TR provides (or most other English sports cars for that matter) which is why I have a TR6 among my fleet of MBs. And I will even go so far as to say that a TR6 is much more fun than an old SL (save for the 300SL of the 1950s) because of the same reasons you mentioned. Having a car that does not need care is like having a dog that does not like people. However, if I had to choose between a 1975 Mercedes SL or a TR6 for a trip from Ohio to California I'd probably opt for the SL. The TR6 is a great around town car, some trips of maybe two or three hours are fine but at least for me, I get beat up driving the TR on any long hauls.

Yes, the forte of the Mercedes-Benz is it's continental long cruising ability. Heck, a 560SEL made it from Manhattan to Redondo Beach, CA in a little over 32 hours. That's what I appreciate about German cars. You get in and are in them for hours on end and don't become fatigued by the end of the trip.

Basically, I value different cars for different reasons. When it's 70 degrees out and beautiful nothing tops a TR6 experience. But when you need to be somewhere and can't risk having a breakdown which could leave you stranded for a while waiting for parts, I jump into the Turbodiesel MB and point it towards my destination without worry.

The TR6 is a bulldog and the Mercedes is a thoroughbred. They're both excellent in their own ways.


OK Bill, your turn

Owner of a fine fully restored british pedigree roadster.
Rick C
Rick Crawford

I'm with Bill on this one my daily is a 02'Volvo Cross Country Wagon go anywhere with anything or anyone on problem. But I still lust to drive my 72 TR6, not a very good start to British Car week here in the Northeastern 48 50 degrees and rain hope to participate by tomorrow. Bill you are right pull over to check something and you've got all kinds of help in minutes to hell with triple A.
Regards, Keith
(what was this thread about?)

Hi All

Keith the thread was about burping hot air and sludge. I believe were still ontrack at least Aaron is after that crack about Bulldogs :)

Seems to be a nice fella just a little mixed up.

I have always looked at Bulldogs as being kind of drab solid built and Butt Ugly but with a tenacious nature and a get the job done attitude. Sort of the MB way? Correct me if I'm wrong here?

Now the TRs have more of a refined racy look and feel. Cranky and stubborn at times yes. But if you sweet talk them and give them enough little gifts in parts and attention. They give you an awsome run and put a smile on your face all day long. In good shape just looking at one sets your heart racing. Fine lines and a great stance. And what a great rear end to look at? Kind of like a fine Arab thoroughbred I think.

I would have passed on this but calling RickCs little blue "MISTRESS" as the plates say, a bulldog just couldn't go unanswered.:)

Heater has a core. Not used much in warm times when we usually use the car. Builds up crap. Go green same as rad. Air passages get blocked. Fans OK just can't move air. And in some cases pump can't move sludge?


Bill Brayford

Just goes to show that beauty is in the eyes of the beholder
R. Algie

Hehe, ok no flames here please...

What I meant by "bulldog" is that the TR6 is a gruff, masculine automobile. Like I said, wonderful in its own way. The exhaust note is to die for and Germany never made anything so "fun" to be in on a nice day (although as I said before, the 300SL of the 1950s). Tolerances in German engines are incredibly fine and they are put together unlike any other automobile. Why do you think there are so many old Mercedes with tons of miles on them? If they broke down a lot people wouldn't keep putting money into them for the long haul. Either way, I love both cars for what they are which is why I own a TR6.


This thread was discussed between 22/05/2003 and 27/05/2003

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