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Engine block sealant

There is a product advertised to seal crakced engine blocks, lifetime garantee, only $100. The 1998 Honda Accord LX in question is presenting with oil in the radiator (frothy, brown gook). The radiator was replaced 3 months ago when we bought the car from a dealer. I am told the problem may be the head gasket or it could be as bad as a cracked block. It will be $1200 to do the head gasket, but it may not solve the problem. Has any one ever tried this sealant product? The car is for my 17 year old son to take to college (125 mile trip one way) needs to be reliable. Please advise.

Get a few quotes on the head gasket repair, get a new timing belt at the same time. Don’t waste your money on the seal. Otherwise, sell it and find another car. You might be surprised what it is still worth even with a bad engine.

Forget the sealer. Even IF it worked for a short time, it won’t be reliable, which you said you need. They’re correct about the diagnosis, it’s normally a head gasket, but it could be a cracked block, or a cracked head. None of them are pretty, but the head gasket is the easiest to repair.

Judging from the price you list for the head gasket, this sounds like a dealer. Chat with some friends, and see who they use to maintain their cars. Hopefully some will be using a local mechanic. Find out who it is, and grab the phone, and call. Ask about a replacement or a good used engine. You may be surprised.


I suppose it is a pretty old car, but did you have a talk with this dealer?

Those chemical sealers are not proper repairs. So if you want the car to be a reliable daily driver you really do just need to get it fixed the right way. That said, those things have been used with success as an effective band-aid on cars that would otherwise be headed to the scrap yard. One poster here (Tester) has indicated that the active ingredient is just sodium silicate which you can buy in generic form for much less.

One thing you could think about instead of having the head pulled & crossing your fingers about the block is just finding a used salvage yard engine.

Great advice. I’m thinking we’ll get some other prices on the head gasket AND check to see what we might get for the car if we decided to go that route. Thanks.

The shop that wants $1200 is not a dealer, it’s a local shop with a great reputation. We will be asking friends and neighbors for other recommendations for shops and will be asking those questions of them. We hadn’t actually thought of replacing the engine, but we will look into that, too. How muchshould we expect to pay for the head gasket replacement if we decide to do it? Any ideas on the cost of a good used engine? How do we know that the engine will be good - is there some way to check for cracks before we buy it?

If there are no external coolant leaks, you get the product that goes in the oil and not the one that goes into the radiator. It would help to name the product and mention how it is to be used.

If the oil is turning gray, the opposite may be true. If a cumbustion chamber crack is involved, nothing will help. The instructions for radiator stuff must be followed to the letter. Even if you do follow the instructions the radiator still might plug up.

There’s not enough known about this car to make much of a guess as to what’s going on but just offhand it does not sound like it’s going to be trustworthy at all.
Some sealers may help a little in stopping various low pressure leaks from coolant passages, etc but when it comes to a combustion chamber breach it’s a lost cause in my opinion and there is certainly no way I want to be on the road with an engine stuffed full of Goop 'Em.

You state the radiator is brown and frothy. This may or may not be a sign of a bad head gasket. They replaced the radiator before but that doesn’t mean they flushed the cooling system clean.

The first step is determining if a head gasket is actually bad. Cooling system pressure test, hydrocarbon test, compression test, etc are a few of the methods used to determine this. The odds of a cracked block are very very slim. That is a diagnosis that is tossed around quite a bit and is seldom ever the case.

When the radiator was replaced, the Honda technician and his “expert” consultant (Honda trained as well) injected some sort of dye and tracked its flow. It was then flushed thoroughly, given a one-hour test drive and let idle for an hour(? - long time as I recall). They were convinced the problem was solved at that time, but the same mix of antifreeze and oil? is what is presenting again. It is an emulsion that settles into three bands: green antifreeze on the bottom, brown (less viscous than oil) liquid in the middle, and then the frothy brown on top. I kept a bottle of it to show any other shops we check out. Good to hear that the cracked block is a rare occurrance.

About 50 years ago, I was able to seal a cracked block on a 1947 Pontiac I owned with a product called K & W seal. It held the year I owned the car and I saw the car on the street 2 years later and I don’t think that the engine had been changed. I would never use the product with a car that had a lot of value, but I had paid $75 for the Pontiac and didn’t want to put a lot of money into it. The crack was around one of the valve seats. The valves were in the block because it was a flathead engine. I thought the problem was a head gasket, so I removed the cylinder head and then discovered the problem. I think I paid less than $5 for the can of sealer.

"The car is for my 17 year old son to take to college (125 mile trip one way) needs to be reliable. Please advise. "

If thats what you are looking for, this car is not it.


I could pose the following question. Why did you buy this car for your son in the first place?

You bought the car, 3 months ago, from a dealer…

No warranty of any kind? It had an existing problem - they replaced the radiator to fix it - and it didn’t fix it.

I would think you could return it, providing you have the repair paperwork, and are willing to fight for what you deserve.

That $100.00 stop leak product is probably just sodium silicate or liquid glass being sold at an inflated price. You can purchase a bottle of sodium silicate from a local pharmacy for about $25.00 and get the same results. You can read how sodium silicate stops head gasket leaks here.


To defend our decision to buy this car… We got a Honda because I have had several Hondas myself and my family members as well. We have found them to be reliable and last for a very long time (250,00+ miles, great in the snow, good gas mileage, nice handling, inexpensive to maintain, etc). This particular car had 149,000 miles on it, was at a dealership with a great reputation, it came with a CARFAX, we had a 30-day 1,000 mile warranty and it was $4,200. I am currently driving a 1999 Honda (170,000+ miles) and I have had it for about 8 years and put in normal maintenance, tires, battery, etc. No major problems.
The problems with this car seemed taken care of for 3 months after they replaced the radiator, by which time the warranty was up. Discussing why we bought the car doesn’t help with the current problem. What is done, is done. I was asking about where to go from here. I received a lot of good information to help us make our next decision and I thank you all for that. We will not be using a sealant. We will be looking into replacing the engine or trading the car in for a newer Honda (different dealership). Thank you all for your help. Signing off…Tmom