Engine Drain Plug

I am trying to flush my cooling system after replacing the thermostat, and I need to get the drain plug out of the engine. The problem is I can't figure out what I need to do this. It looks as though the opening is square, but I cannot find anything that fits. Please help, I need it up and running by friday for a trip.

It is square, and an odd-ball size. Someone not too long ago posted what size it is -- I think it was 5/16" but not sure of that. What the person said he did, IIRC, was buy an inexpensive short square drive extension and grind it down to the necessary size.

Yes, you need to use a pipe plug Msocket. The drain plug on the side of my 88 XJ block. You need to buy the 5/16" pipe male plug socket.

Buy the socket from who ever you want but to help you out here a picture : http://www.mytoolstore.com/sk/sk03221.html

I tried to grind down something to fit but it did not work for me, I tried the pipe plug socket a buddy of mine picked up off a tool truck for me and it goes into the square hole and I can tell it is the right tool. Next time I change coolant I'll pull the drain plug using the pipe plug socket.

If you can't find the tool you can fill the engine with water and drain it. I figured out if I was getting 2 gallons out each time I'd have to fill and drain the engine 4 times to get the concentration of old coolant below 2%.

I would pour in 2 gallons of distilled, let the engine idle for 5 mins, then let it drain. It took me an hour or two to do the 4 fills and drains of distilled.

I used distilled water because a coworker who use to work at a Military Nuclear reactor told me to only use distilled. Distilled keeps you from introducing chlorine, plus all minerals in your local tap water, these can deposit on your block and radiator. The same guy told me how this one nuclear plant on the east coast had to shut down and replace the pipes because the utility did not monitor chlorine content.

At 89 cents/gallon of distilled the peace of mine was worth the 5-10 bucks it cost me to buy the water.

If you need to get the job done today consider the multiflush with distilled.

Not meaning to thread hi-jack, but is it in the same place on my '01? Thanks

Ary

Ary,

Unless they changed the block which is hightly unlikely then yes it is in the same place. It is located on the driver's side, about an inch above the oil pan and around the 5th-6th cylinder.

I recall reading posts that HO 4.0s still had the fitting for the knock sensor used on the non-HO engines. Once a casting pattern is made they don't change it unless there is a good reason. It costs alot to modify a pattern and validate the block works the same.

Martin

Why not just intstall the prestone T fitting, the prestone back flush kits do an excellent job and don't require the contortions of pulling that plug. I have been using those kits for years on many vehicles and most 'professional' auto parts stores sell the T fittings in assorted sizes all by themselves. Means you can buy one 'kit' and use it on multiple vehicles. Not bad for $5.

Ok, I changed the coolant today. Getting the plug out wasn't that bad once I got a piece of bar-stock that was 5/16's square. Then just threw a wrench on it and presto, coolant in my eyes Anyway, got it all drained and refilled, but I had 2 qts left over(according to capacities listed in the FSM). I'm wondering what the proper procedure is for burping. I'm carrying around an extra gallon of 50/50 just in case, but honestly wouldn't know what to do with it if I needed it. THanks

Ary

P.S. It was in the same spot....

I installed a prestone kit, but I did not know this would drain the whole system, because the directions only say to open the drain cock after runing the engine (I think that is how it goes, dont have the directions with me). Would there be any benefit to draining it from the engine block? I already ordered the socket from car quest, but I haven't paid for it yet, I guess I could have the guy send it back. Wouldn't it make it easier, and make sure that you get everything out by using the drain plug?

Mich,

I'd still buy the socket and keep it around, next time you change the coolant you may wish you had it to remove that block drain.

I don't know how you do it but I change my radiator hoses every 4 years. Rather do service than have it blow a hose hundreds of miles from home. I do the same with fan belts.

Martin

To me the object is to flush the system, not drain it. When I do it I hookup the back flush kit, attach a hose to the bung extension, flush the exisiting 50/50 mix into 5 gallon containers. Once I have water in it I add the cooling system 7 hour flush and go drive it. Then I reflush the system and add a gallon of pure antifreeze, from then on I add 50/50 mix made up of antifreeze and distilled water and check the mix with a mix gauge. I do end up with a gallon or two of tap water in there but my well water is pretty good.
I have also used the drain on the side of the rad but decided that using a hand power pump is less hassle than removing the grill.

What is a 7 hour flush? I used the a prestone flush, (the general one in the small bottle, not the one for hard deposits) but didn't see a 7 hour flush. Is it any better? Can I get it at autozone, I didn't see it there when I bought the other stuff.

The short quick flushes are somewhat more abrasive and harsh. The 7 hour flush is a bit more gentle. In the past every time I have used the fast flushes I have ended up doing a water pump in short order generally because it starts leaking out the weep hole. I first used the original 8 hour flush from prestone on my 82 S10, that truck had 680,000mi on it when I sold it and I only replaced the water pump 2x and the radiator 3x but that was before I started using distilled water. I watched the 8 hour flush work on the day I decided to use it, put it in the nite before , next morning I drove from the poconos pa to syracuse ny on a service call, then home. Checked the rad when I stopped for lunch on the way up, again when I got to the customer site and on the return trip. By the time I got home that nite the rad looked new inside, all the green and brown stuff was gone from the ends of the tubes and the solder looked new. I have been sold on it ever since. When you have to use your vehicle to make a living you use what works for you.
One thing I did learn from a local rad shop, he showed me how to check so see if the copper fins are 'rotted' by running the backside of your fingernail along the fins, not too hard, only enough to deflect them, they should spring back, A rotten one won't, the copper gets old and a rotten one does a really poor job of heat transfer.

I just back flushed the coolant system, and I went to pull the drain plug on the engine (with my $11 male pipe plug socket). When I did, it slipped out and rounded off, I don't think I will be able to get it out. Any ideas on how to drain the water out of the engine without pulling the plug?

Mich,

On the non-HO engines the coolant temp sensor is located directly behind the engine mount bracket on the driver's side. If only a 1/2 higher than the drain plug so you will get most of the coolant out.

Make sure you use a flare wrench when trying to remove the sensor. I did not, rounded it off, and ended up paying the dealer mechanic to remove it.

If you are a bold guy you can cut off the wires so you can put a 6 point socket on the temp sensor and turn it out. Make sure you have a new sensor in hand before you start cutting the wires.

I still like my fill and drain with distilled 4 times to get the old collant out.

Martin

Martin, first, thank you so much. You have be so helpful to me with every post that I put on here. I cannot think of one topic that I posted that you did not answer. I would be willing to bet that everyone on this forum has been helped by you, and I do not think you get enough credit. So again, thank you very much. Second, I just wanted to let you know that I did get all the coolant out using the back flush kit and letting it run out of the radiator until it was clear (just didn't want you to think I was stupid). I never thought of pulling the sensor though, thanks! Just for mixture purposes, about how much water do you think is left in the block after you drain it this way? That way I know how much straight coolant to add if the amount is significant. Thanks again, Chris

Chris,

The book says the cooling system is 12 quarts. As we know you can not get all the water out of the block so what to do.

On my 88 XJ after I flushed it I poured in 6 quarts of full strength coolant, then topped off with distilled. I have to trust the capacity in the book is correct. After you fill you can use a tester to see if you are at a 50/50 mixture.

So just dump in full strength coolant and top off. After I did all my flushing last year I decided to run Dexcool in my engine. I have a 2001 Buick le Sabre and only wanted to have one jug of anti freeze around. I think green or dex cool will work fine now that you have flushed it. I changed to Dexcool to simplify my "logistics". I also installed a Hesco water pump with an aluminum impeller so figured the Dex cool was a good decision since it was developed with aluminun engine in mind. Dexcool has a lower pH than green. They are both Ethyline Glycol, just dex has more addatives.

If you do go to Dex cool I suggest you buy the Havoline brand. Havoline is the supplier for GM, Prestone was developed as the second source, so the Havoline people know what going on since they did the development.

Martin

You know, after following the directions of letting the engine come to operating temperature after adding the prestone super flush, I noticed that it comes to a boil and spews out from around the cap. I think this means that the cap is bad, doesn't it? I was going to order a new one, but I just thought I would check if it was bad before spending the $9 for a new one.

I do a new cap every year when I flush the system. Cheap insurance and I keep the old one as a spare. I also have one of the stant test kits with the pump, pressure gauge and adapters for pressurizing the system and testing caps and such.

If you still have the pressure bottle then it is normal for it to reject too much fluid. It all part of getting the air out of the block, did you let it run for a while with the cap off, you know let the thermostat open, before you install the cap?

If you order get 2 of them, always need a spare on hand.

I would consider replacing the pressure bottle, you can get a new one from quadratec for $20, and it comes with the pressure cap.

The cap our XJs use seems to be a dealer only part. When I went looknig for a replacement a few years ago is when I found this out. A lot of online listes list a 13 lb "normal" cap which will not work on our pressure bottle.

If you are doing all this cooling system work I'd install a new pressure bottle, it is the weak link in the system and if you get it from quadratec it not that much.