After going through my whole cooling system I've concluded that my head gasket has a hole it it. I really don't want to do a whole head removal and a friend told me to try putting Blue Devil gasket sealer in my coolant and it will seal the gasket. It sounds risky; has anyone tried it?

Thanks for any responses based on experience.

Larry

1997 XK8 convertible
BRG
Dayton Wire wheels

 

I wouldn't do that. Anything that can seal a bad headgasket will also plug passage ways in the cooling system.
How did you come to the conclusion that it's your headgasket?
Start from the begining and give us your problem and what you have done. I wouldn't want to start surgery on the car without a second, and possibly more, opinions.

 

Bob's right- I wouldn't put anything in there- confirm you have the problem you think you have before moving on. There could also be other peripheral issues you may not be aware of depending on how hot it got.

I am working on an XK8 with a "broken timing chain" Zero compression on one cylinder pointed to confirming that fact but when I removed the head I sadly found that there was a dropped valve seat. The right way is usually the best way to diagnose and fix a problem.

 

IMHO, these products are part of the retail car maintenance pre-sale products. They are meant to provide a temporary fix so that less scrupulous folks can sell a car in running condition, and let the new owner deal with the mess when the leak invariably reoccurs. Don't confuse this with a true fix for a car you want to keep...

 

If you cheap out on a car like this, then be prepared for when it comes back and bites you on the ***.
If you can do the work yourself, it's only the cost of parts and your time.
If it goes to a garage, then raid the rainy day money.
If you "think" it's a head gasket, first be sure to prove it is a head gasket (milky oil is a good indication, unless you have an oil cooler problem which gives the same)

 

Thanks to all for the comments, all of which seem obvious. I was dubious about the Blue Devil to begin with. But I just replaced the timing chain tensioner a year ago and the thought of another major project is daunting.

To to answer one of the comments- the car has been overheating with extreme pressure buildup in the hoses. The water pump, fans and thermostats are working fine. I've gone through the whole cooling system including the radiator and found no clogs. Any more troubleshooting advice is appreciated.

Larry

 

Silly question I know, but did you replace the thermostat and is the car fully burped? I've had scenarios where there was an air pocket that caused what you are describing- after burping had no more issues.

 

Or do a cylinder pressure test.

Have you forward and back flushed the system?
Including through the heater matrix?
Any milky oil?

 

You can also buy test strips that can show exhaust gas residue in the coolant. If you have the kind of head gasket leak that pressurizes the cooling system, these would seem appropriate. I believe they are available at the parts store, or even Amazon for fairly cheap.

A word of caution: If the compression pressure makes it in the cooling system, the coolant could make it in the combustion chamber and fill it up. On the next start, you could face hydro-lock as water is incompressible and cause more damage.

I agree with others, firm up the diagnostics as much as possible before starting a big job like this. A couple of observations: don't run the car without a thermostat. Confusingly, this leads to overheating as water flow is disturbed. Also, try and figure out if there is a mix of incompatible coolants as they can gel and clog the system. Try and run the car with the expansion cap off to see if there are any bubbles. There is of course the presence of white smoke in the exhaust as another clue.

One more thing: Check if you have any heat in the cabin. That heat is brought into the heater core by a separate pump that is known to go bad over time (brushes wearing off, if you can believe it!). Not positive a bad pump would block the flow, but it is worth checking.

Best of luck, keep us posted.

 

Thanks for the reply and meaningful discussion, especially Mr. Mertz.

I have never "burped" the system after doing work on the cooling system- right now I have the hoses and water distribution pipe off, the radiator out, and the cooling fan assembly off.

When this first happened, I was driving about a mile from home and the car began to jolt. The "idiot gauge" was maxed to hot, so I pulled off and let the engine cool. When I arrived home (after a couple more cool-down repetitions) I opened the retaining tank (..yeah, I know- never do that..) - the hot coolant spurted up; I covered it back up and when the engine completely cooled down the hoses were puckered in (see photos).

The radiator is flowing; the pump and thermostat are working and the fans kick on when they should. BUT- the coolant looks and smells fine and the oil does as well. I'm very puzzled.

 

How did you determine that the thermostat was working properly? A very common problem is for it to be stuck in the closed position or just barely opening resulting in very rapid overheating.

A head gasket leak will result in white smoke from the exhaust on start up.

 

Did you check or replace the pressure cap? Faulty radiator caps, in our case the pressure cap in the coolant reservoir, can cause collapsed radiator hoses and expanded ones too. They're supposed to regulate pressure by venting to and from the overflow tank via the overflow tube. If they don't work properly, the coolant may boil and create steam at too low a temperature. Then after cool down, any pressure might not be released causing collapsed hoses. Maybe this $9 part is all that's wrong. A clog near the coolant reservoir or in the overflow tube might cause similar problems I would think.

 

Do the exhaust residue test first. It's cheap and effective. If it comes back positive, you have a blown gasket to the cooling system. If it comes back negative, then you may have a cooling system problem.

One thing I would strongly advise is to not continue driving it if the system is over pressurizing. I blew a heater core that way which was a very unpleasant consequence.