Eliminating coolant nipple from rear housing
 

I guess this question belongs here as much as anywhere.

On my race car, there is no heater core. I am also not using the stock water pump housing where the heater core return is.

Therefore, I would like to remove the coolant nipple from the rear housing and plug it rather than loop a hose around.

I have removed the nipple. For plugging, I see a couple of options:

1. Tap the hole. I like that idea most, but the area is pretty thin and I don't want to crack it.

2. Install a freeze plug. The hole appears to be 17mm and I haven't found any compatible plugs.

3. Weld something in there. I don't want to do that unless I have to. If I do go with welding, I'll fit in a threaded bung.

I just thought I'd throw this out there in case anyone else has solved this problem.

Or go down to the local autoparts store, get a 5/8 heater hose cap, cap it and use a small hose clamp. Badaboom, badabing.

PaulC

I have concerns about whether or not that would hold up. Considering the pressure that would exist with my powerful electric pump in conjunction with a closed t-stat, that's a lot of pressure to hold off at a dead end with a hose clamp.

Consider also that this will run at even higher pressure because, with a stock setup, when the t-stat is closed, the pump can still circulate through the heater core. In my case, the only relief will be through the t-stat's bleed hole.

Maybe I'm making this more complicated than I have to, but I've never seen anyone plug this that way. I guess it's pretty easy to test with an electric pump :).

the early cars had a screw in hose barb, or they had a bolt to block it off. mazdacomp will know what it is, you will have to thread your housing for it though

mike

At the most it's what, 19psi? That's when the pressure cap pops, so I doubt there's a heck of a lot of pressure there.

PaulC

Oh, and just to say, I have a cap on the end of my heater line, ran it for two events now, no problems.

PaulC

I have done this three different ways on three different engines. best and last one I tapped out the hole to a pipe thread and installed a threaded plug. I have also filled the hole with A/B epoxy and I have used the rubber cap and clamp. all have worked without failure, but I like the security of the threaded plug.

The in-block pressure is typically a lot higher than the radiator cap pressure, so saying the cap pops at x PSI doesn't mean much.

I went a long time with a simple block off that worked very well, although it was a bit heavy. It was a 2" length of heater hose clamped onto the nipple, and a pipe plug doped up with aviation sealer (the brown icky stuff that never washes off, gets everywhere, and smells awful in the process) jammed in the other end and clamped with another hose clamp.

I wouldn't trust most of those cheap parts-store block off caps... most of them are rather thin rubber that likes to blow out, because they go soft when they get hot. If you must go cap, get a thickwalled one, the kind that are like a REALLY BIG vacuum cap.

I used a Toyota :eek: part on my last race car. 86-91 Supras have a heater hose block off that is a very thick rubber cap. I held up perfectly for 5 years of racing.

I think the part number is 90339-16001 and should be about $4. I may be off with the part number, since it's been 4 1/2 years since I left Toyota.

May I ask what size you tapped it with?

I like the security of a bolt as well. I REALLY don't want to have my cooling system blow out for something so trivial.

The only other person I've seen with a track only engine, actually looped the cooling system from the rear housing to the front. I don't want to do that.

that seems to work too, although it looks messy, and it puts another hose in the engine room

mike

I believe it was 1/2"NPT but check the size after removing the nipple.

I checked 1/2" NPT but I thought it looked slightly large. I thought 7/16" would be good, but I've never seen a 7/16" NPT anything before.

Does anyone know if I am correct in believing that the only way to tap for AN fittings is going to be welding in a bung?

Thanks for all the responses. I think I'll try the 1/2" NPT. Should be easy enough to repair the cast housing if something goes wrong :).

on your tap or tap chart it should give the drill size for the 1/2"NPT tap and verify before using. if it is slightly larger you will be ok, if smaller drill out to correct size. I didn't have to drill, I just cut the new threads. next larger pipe size would be 3/4" NPT. sorry cast iron can't be repair very easily so be careful.

I tapped mine and installed an an fitting with a cap on it in case I want to/ need to use the heater at a later date. I'll have a look to see what size it was for sure but I think I used 19x1.5 so that I didn't have to drill the hole (since the wall is so thin.)

Matt

That would be appreciated! The size of the nipple that came out is 17mm, so 19 is probably quite close. Like tims said, I can just check the drill size recommendations to figure out what size to use based on the 17mm. So, you didn't use an NPT thread then? I suppose you must have used something to seal the threads? Pipe dope or RTV or something?

I am honestly a bit concerned about using an NPT thread anyway, I worry that the surrounding cast would crack when I try to tighten the plug.

use the straight thread AN fitting if your worried about the NPT fitting. use some pipe dope on the npt and the AN should have a crush washer and a cap. either will work and neither needs to be tightened a great deal. remember all these fittings are aluminum.

Have you ever seen a rubber freeze plug? They are a rubber cylinder with a washer on each side and a carriage bolt running through the middle. The washer on the outside is a little larger than the rubber. When you put it in and tighten the nut the washers compress the rubber and WALA! problem solved.
When I used to race Pontiacs I ran through so many blocks that all I used was rubber freeze plugs. I'd break and yanks 'em all out and throw them in the next one and go. They were mainly designed for when you have a freeze plug go out and you don't have enough room to knock a steel one in. As long as you can get the old one out all the way it keeps you from pulling an engine in many cases.

WTF did this get moved? That's a race car topic, pure and simple..

PaulC

im moving it back :)

thanks Greg!

Nice Avatar btw

We've always used freeze plugs.

Dangerous. This is the approach we took in building our car. During OTC we began leaking through a cap on the third day. (at Willow Springs.) We replaced it and continued on... This last weekend the rear one ripped open out at LVMS. We may have lost the engine because of it. (although there is some question now).
There is no way I am taking my car out on the track without using a more secure solution again. Its too damn risky. Two failures in 8 track days when messing around with a $4k rebuild is too much...
-Matt
'87 Turbo II
'88 GTU

I just checked the tap and apparently it was a 16x1.5 not a 19x1.5 as I mentioned earlier. Best thing to do would be to check the hole with a drill bit, since I beleive mine is not in the block, but in the part of the press fit nipple that is stock. (The nipple was cut off flush with the block, but I don't know if there is still some of the nipple in there since I wasn't the one that cut it off but I'd guess there is part of it left if you said that the nipple that came out was 17mm)

I used pipe dope and a crush washer for my install.

Matt

Agreed, but 8 days of hard racing is hard on parts, no question. Plus it's a turbo car. I need to wire a warning light for water temp so this doesn't bite me in the ass, but so far i've run 2 events, no issues. We'll see.

PaulC

GUYS, BRILLIANT BRAINSTORM THANKS TO A MENTAL NUDGE FROM SILWORM:

We have a problem with rear apexx seals going bad. We need to monitor the rear rotor more:

Why not tap the hole and install a temp sensor in that location?

That is definitely one of the reasons I favor the tap idea. But, if I were you and I didn't have another reason to tap this location, I'd pick another one. I believe that, on the 3rd gen at least, there is already a temp sensor on the rear housing under the oil pressure sender. There are two temp senders, one in the neck and one in the rear housing.

I don't know how the stock setup uses the two of them for certain. I've never confirmed this, but I believe I was once told that the sensor in the neck is the one used for the guage and the one in the rear housing is used as the temp input for the ECU.

Opposite, the one in the neck is for the ECU, the one in the housing is the guage sender.

PaulC

My set up is not in a 7, but I taped into the upper water outlet (above the t-stat) and routed the hose from the heater to this location. My reasoning being that the water would always be circulating through the radiator as it exits the hotest part of the motor (combustion side of water jacket). I figured I could get better flow through this area to keep temps down.

Down side, it takes longer to warm up - but for race car its not a problem.

Hmmm... why run a t-stat at all if you're going to do that? I'm not being facetious.

The stock configuration routes the heater core outlet back to the lower radiator thus allowing the pump to constantly circulate. One of the reasons that I don't want to loop (in addition to simplification) is that I think that there would be a beneficial increased static pressure in the engine generated by the pump when the t-stat is closed which would help reduce localized boiling.

Just a thought.

My vote is drill-tap-pipe plug. It will never blow off while your on the track. If you don't know much about tap sizes or reading tap charts thats ok because I've noticed a lot of hardware stores sell "kits" that have the drill bit and tap in one package. Id stay away from caps or anything like that.

1/2"NPT is the winner.&nbsp This will work at least on the top fitting - can't confirm for the side one.


-Ted

I don't run a thermostat - not really. My thermo has the edges drilled with 6 , 3/16" holes to allow water to flow even when it is closed.

Seems to work well, even in a much smaller engine compartment with a limited radiator size.

Just to add a bit more to the caution regarding the hose cap- on a 280ZX I had, I replaced a hose cap 4 times in 10 years.. The package I bought it had two in it, and I'd keep the other one in a convenient location because I knew I'd need it sooner or later.

Could you use the coolant nipple as a turbo coolant line?

dp

The majority of the streetish engines I have had around for a long time all have had that mod at one point or another.
Die Grinder off the steel portion.. then pipe tap the steel/cast remains and then go to Home Depot and buy IIRC (It is late) 1/4" pipe tap for the upper rear pass side that was for throttle body heat.. and 1/2" for the heater core feed portion.
Then a swirl of thread teflon tape and snug into the holes some pipe plugs.
Done.. No leaks no drips no hose clamps.. no pieces of heater hose with Lug bolts in them.. or whatever things people will find to stick in there..

The nice part?
If you want to go back to a heater etc.. you unscrew the plug and put in a pipe.

Not that I would ever want to put street stuff BACK INTO a car... eek.. that is sacrilegious.. I mean I have heard of this.. "Restore" thing.. but have not seen it yet.

how do yuo prevent the chips/metal from going into the coolant if you drill and tap while teh engine is isntalled in the car?

i know people dont like it, but what about some JB weld, then put a nipple over it? I would think JB weld would block the hole quite well. Because if you try to tap it on the car, you will most diffenetly get shavings in the coolant.

It is a trick.. but it is easily done.

Lightly oil or grease a dowel rod that you buy from the local hobby store.
Then lightly tap it into the hole so it is firm.. almost snug.. but you can still pull it back out.

Using your Air grinder, or Dremel.. cut off JUST the metal portion... It requires a gentle touch so you cut off OLNY the metal and not through the dowel.
Then when you have cut all the way around.. The grease/oil prevents and tiny particles from getting into the water system.

Then with the rest of the water system closed off put a hose into the opening of the water filler with it turned on lightly..
This will cause a small jet of water to come OUT of the hole you now have.
Then take your Tap and carefully start threading it into the hole till you are deep enough to put the plug in properly.
When you back it out it will allow any thread particles to jet out the flutes in the tap. (As it does when threading it in)

DO the same on the larger heater hole but use a larger dowel. (After plugging off the small hole)

It works nicely.. And yes when you start tapping you WILL get wet. It sprays out a bit when you first start cause of the tightness of the tap.
Dont get all carried away and have such high water pressure that it blows the tap out of your hand. Just enough so you are keeping a flow that is coming up out high enough to prevent the particles from dropping into the coolant passages.

OH yes.. go back and forth A LOT with the tap to keep making your cuts smooth and the particles small. The water will keep the tap cool and lubricate it as well... of course not as well as tapping fluid.. /shrug

Thats how I have done it... your mileage will vary with the skill and ingenuity level of the applicant.. :)

thats seems alittle to risky for me to try, but are there any doubts on JB weld and a nipped over it?

Ehhh.. if you dont feel comfortable with a mod.. DONT DO IT... :) It is really simple.. If you have thoughts that is may not go well.. thats a good reason NOT to do it.

JB weld? Ehh.. not something I have much experience with.. I imagine it could work.... But I think I used it on a goKart in Jr High.. and it didnt work too well IIRC... but I dont really remember what I used it for at this point.. it was a LONG time ago. Prolly.. well.. more than 20 years ago. :(

I would try it by "welding" a cap of sorts over the larger heater pipe.. that way if it doesnt work you can fairly easily chip it off afterwards.

spin have u actually done that procedure to the water pump housing? Cause i would think the metal shaving would be heavier and easily fall

i mean rear iron not water pump housing

Yep.. Just make sure that you have decent water pressure etc. so it is jetting out etc. while using the tap. AND make sure not to get all heavy handed and do all the cutting at once. Cut a 1/4 turn at most.. then back off.. then 1/4 then back off etc..

As I said.. if you have reservations.. DONT DO IT.

/shrug

Didnt have any problems when I did it on the old assembled motors.. but again.. I was overly careful and made sure things were right before starting to cut thread.

I know that some on the forum (SHift Mad Quick Yo!) may think that since they read it they can do it... and get out a air chisel to do a port.... OR they can do a 20B swap for 5K out the door.. turn Key! And make 1K hp to boot!

Then again there are many that cant.

Most are in the middle in one way or the other.. from very little wrench exp.. and good motivation.. to Much too much grease under the nails.. and not as much motivation..... but years of Exp.

Then there are the shift mad quicks.. and the Rick Engmans.. I think we are all in the middle.. one way or the other.

If you feel confident.. give it a whirl. Worst case scenario.. you do something like break off the tap in the iron housing.. and Now you have a good reason to port your motor! Oh yeah.. I guess if you were heavy handed with the tap.. and brute forced the thing.. you could crack the iron. But again... that goes to the exp thing..

If you are comfortable.. go fer it. If not.. buy a 5 buck hose and run it to the waterpump.