Head Gasket Leak goop? Bears True Blue? Bars? Is it nonsense?
 

Earlier I posted about my '83 240d that had an overheat event while my son was driving.

Bottom line, I'm pretty sure I have a blown head gasket (or maybe a cracked head). The engine runs fine, but after 5-10 minutes at medium rpm, it overheats. I have a large funnel that fits perfectly into the radiator neck. I filled with water while fast-idling the car, and after the stat opens, you see bubbles coming up out of the radiator every now and then. I believe this is exhaust gas.

Youtube is full of videos of people swearing by various head gasket leak sealers. Barrs, Bears True Blue, many others. I watched the Bears how-to video and they are quite specific on the process. It is not just dump it in there and forget it.

Have any of you had any experience with these products?

Junk, especially so with the high compression diesels have.

using any of that will result in a very badly clogged cooling system.

Pull the head and fix it properly. If you dump that stop-leak crap in your engine, you may as well save your money and tow it to the recycler now.

This x100.

It's a damn 240. It doesn't take much to pull the head at all.

Stop-leak junk is for beater cars that are knocking on the junkyards doorstep and you just need it to last another month or two.

Doing a leak down test to determine what cylinder is leaking to coolant then pulling the head is the best fix.

Pumping air into the cylinder and looking for bubbles in the radiator is _the only reliable way_ to confirm combustion to coolant leaks. Using a chemical test kit only finds large leaks and won't tell you what cylinder is leaking.

However, I have direct experience with many sealers across many cars.

Plain sealer won't work on a combustion chamber to coolant leak, they are for external leaks.

Bars Leaks tablets are fine for seepy external leaks but does nothing for combustion to coolant leaks. It is so good, GM and other auto makers recommend it for seepy leaks and sell it under their brand. This will not clog a cooling system that is in any decent condition and is stealth. It is a super fine powder containing mostly Ginger.

Blue Devil brand head gasket sealer will take a large head gasket leak to near nothing or zero. This contains Sodium Silicate ( AKA Water Glass ) This won't clog a cooling system either as Sodium Silicate remains suspended in water and only solidifies once the water is strained out by the leak.

BD will not work on a slight combustion to coolant leak. I've used this on an engine that used 1 qt coolant over a few months with minimal positive results. After pulling the heads, the gasket looked near perfect with very slight discoloration in one area. The heads had developed a very slight depression in one area resulting in less gasket clamping force. ( This was an iron block / head GM V6 )

Thanks for the detailed response. Can you suggest a fitting/adaptor for putting compressed air into the cylinders? I guess I'd need something with a shrader valve that would thread into the injector hole. If I had an old injector, I could braze that up. Is there on off the shelf solution?

Thanks-

I've used the Harbor Freight leak down tester to good effect....

Is was about $50 IIRC .

Your are welcome.

A compression tester adapter ( injector or glow plug mount ) works fine if you remove the check valve ( usually a tire type valve with a very light spring ). You do not need a dual gauge leak down tester.

Remove the radiator cap, fill rad to top as this helps ID a leak.

Turn the engine so both valves are closed / piston at top then pump in 90 or so PSI air. It may take a few times to get the engine exactly at top and the air might rotate the engine so give it a puff of air first. Stay clear of the ran and belts.

Let the air run for 10 - 15 seconds then look for bubbles in the rad or a rising level of water. Be careful, a very bad gasket / head will result is a spray of water from the rad.

The HF leakdown tester only has spark plug adapters. It'll work but observe pressure limits & use instructions included to the letter.

The HF diesel compression tester has injector or GP adapters that'll work if you remove the schrader valves. If you go to a hose shop, you can probably get the adapter(s) you need to plumb the injector or GP adapter to a quick connect or schrader inlet.

Here is an update on this thread.

I did a lot of research on head gasket sealing potions. There seems to be 3 types.

First, there is the Barrs sealer type which has copper flakes in it. The idea is that the copper flakes get lodged into the leaks in the gasket. It gets hot there and they melt and stay put. I have two friends who used this in Subarus with head gasket leaks, and they reported 100% success.

Second, there is the Sodium Silicate (aka waterglass) type (Steel Seal, Bears Leak, others). This stuff apparently cures at a specific temperature.

Third is the type made by Titan Sealers (actually, they claim to be the only maker of this type). It is a polymer that is designed to cure at a temperature that is high enough that it only occurs at the head.

I decided to try the Titan sealer stuff.

I drained the radiator and block, removed the thermostat, and bypassed the heater core with a piece of copper pipe. I put in the titan seal goop and filled with water. I did 3 run cycles of 20 min idle, 20 min rest, then overnight cool. The next day I took it for a drive, and amazingly, no overheating.

I'll continue several test drives like this before putting the stat back in and reconnecting the heater core, then draining and filling with anti-freeze.

So- not totally out of the woods yet, but it is looking good so far. How long will it last? Who knows. But I do know that I do not have the time to do a head gasket on this car.

All sealants works on the principal of plugging the leak when the material in the coolant is heated by the combustion gases. The material solidifies and viola, it plugs the leak. I used Blue Devil which is silicon sulphate. It turns into glass when heated. It works for 20k miles on one of my sdl which is pretty good, all things considered. It is definitely not 'permanent' but a good salesman tool to sell the car. If you are selling the car then it is good to go. If you are keeping it then it buys you some time but borrowed time. May be 1 year or so. The other thing is to NOT pressuring the radiator if you think the car is ok. My experience is that pressuring the radiator may dislodge the plugging material. Good luck.