hi guys,
problem on 1993 940 2L turbo estate.

Been running with suspected internally blowing head gasket (bottle getting pressurised and blowing coolant out). This has opened up an old heater matrix wound previously fixed with rad weld. Tried using K-seal and now my car stinks of putty. Just drove 10 miles home from town with steam pouring out of the heater vents. Family not impressed with driving home with all windows open and steam pouring out everywhere! Anyway this car has used up all its available budget for the year so I'm going to bypass the heater matrix and wear my motorcycle gear when I drive it to stay warm. Is it just a question of connecting the two one inch wide hoses together with some copper pipe and a couple of jubilee clips - the ones that go into the bulk head near the exhaust manifold?

Sometimes the expansion tank cap fails like you describe - something to consider replacing if you haven't already.

Also, try Irontite sealant (Blue "All Weather Seal"). I'm not sure where to obtain in UK (I paid $18 in US, bought at a machine shop). Works on both head gasket and heater core. Stopped my head gasket leak four months ago and still sealed today.

Dear pierso,

Hope you're well. Sorry to hear of cooling system problems.

There are two ways to isolate the heater core. The first involves - as you suggest - connecting both heater hoses, using a short length of copper tubing and screw-type hose clamps. If I recall correctly, the heater hose is 5/8" internal diameter. Therefore, 1/2" copper tube may be too narrow. To add to the diameter of the connector tube, solder a connector-piece on each end of this 1/2" diameter copper tube. This "connector" - used to join two lengths of 1/2" tubing - should be readily available at any hardware store/ironmongers/plumbing supply store. It should add enough to the diameter of the copper tube, to allow a tight seal between the hose and the tube.

If the heater hoses are factory-original, they're well past their working life. Bending them to allow this re-routing will add stress, and possibly cause failure, total coolant loss, and make urgent the replacement of the head gasket.

To minimize this risk, it is better to remove the heater hoses entirely, and to replace them with a short section of factory-fresh heater hose, which can be had at an auto supply store. When the headgasket is done, it is easy to access the heater hoses, and to replace them with factory-fresh items. Use Volvo-branded heater hoses. The added cost buys peace-of-mind that the new headgasket will last many years.

Rout the replacement hose from the end of the steel coolant pipe -- that runs from the back of the water pump behind the exhaust manifold and around the back of the engine -- to the coolant hose port on the intake manifold side of the head, between the third and fourth intake manifold runners. Secure each end of the hose with the screw-type hose clamps, that should be present.

As the system is subject to over-pressure because of the failed head gasket, do not trust spring-type hose clamps to keep the heater hose loop in place. Screw-type hose clamps are a must.

Hope this helps.

Yours faithfully,

Spook

many thanks for advice, have installed a U shaped piece of 15mm copper tubing for now as short circuit loop. Will follow your good advice and get some 5/8 tubing from work tomorrow to run from back of water pump round to inlet side of the engine.

Just one thought . . . is there any likelihood that the head gasket may not be gone as suspected. My back up theory is that when coolant is ejected via the heater matrix, the system cools down drawing in air which then expands quickly when the car heats up next time and pushes the coolant out of the top up reservoir cap vent. Grasping at straws? Haven't got it compression tested yet as have been putting off the possibility of doing the head gasket in the street in UK winter.

regards
pierso

Dear pierso,

Hope you're well. Any "tubing" - this term can refer to a range of materials, e.g., copper, steel, plastic, &c - for this repair needs to be purpose-made heater hose. Heater hose is made of rubber, compounded for long-term resistance to heat, and reinforced to stand-up to cooling system pressure. Thus, I'd definitely not use just any rubber hose. That is a recipe for disaster. With rubber products, there's no easy way to know what ingredients have been used, and how those ingredients have been processed. These factors make a huge difference in durability, etc. Thus, when it comes to heater hoses, use Volvo brand hoses.

I've replaced several sets of heater hoses, all factory original, that lasted about 15 years. The cars, on which I did this work, spent the first half of their lives in the southern part of the US, where average ambient temperatures are quite high. In a climate that on average is cooler (UK), heater hoses might last a bit longer. Even so, while the Volvo product is more costly, it brings peace-of-mind, especially if you've just done a headgasket.

A competent mechanic should have a test kit, to see if there are exhaust gases in the coolant. If so, the headgasket has failed. If not, then I'd do a compression test. The test for exhaust gases is simple and fast and should not cost a fortune. I'd have that done, before opting for a compression test.

It is possible that various anti-leak compounds have partly plugged the radiator, creating back-pressure, when the system is at operating temperature. I'd not use a stop-leak product for fear of plugging-up things other than where there's a leak. Thus, in a cooling system, I'd fear plugging-up the heater core, which is hard to access.

Based on several years' worth of reading posts on this Board, it seems that headgaskets want replacing at 250K miles (400K Kilometers), unless exceptional care has been taken. If a headgasket change is needed, I'd also replace the radiator, unless you're 100% sure (dated receipt with part described) the work has been done.

Hope this helps.

Yours faithfully,

Spook