ANOTHER cracked water pump housing...Water Temp Question

[Newbie]

I had yet another water pump housing crack. Luckily I found one and got it replaced before the race this past weekend. I put the belt on and made sure it was pretty loose. After a 15 minute practice session, I came in and checked the housing and belt tension. The belt was substantially tighter, I assume its from metal expanding under the hot conditions. I also assume that the past 2 housings cracked when the belt tension increased due to high temprature expansion and harmonics.

I loosened belt tension a little more and it held for the whole day.

My water temp is very high...250 when running water with water wetter. It's a brand new oversized radiator, and I removed the thermostat...No fan (will an electric fan provide better cooling than air at race speed?) It cools down quickly when I back off during cool down... Any ideas on how to get it lower? Is this operating temp normnal?

Thanks,

Steve "two more races 'till I shed my X" Smyczek

[C. Ludwig]

That's to high on water temp. You say you removed the thermostat. Did you plug the bypass hole that's located under the thermostat? If not you need to and that will help to lower your water temps.

Also, oil temps effect the water temps. Where are you oil temps running? If they are high you'll need to address those. Bringing the oil temps in line will usually bring the water temps down substantially. Proper ducting and making sure all the air goes through the coolers and rad and doesn't spill out the sides or bottom is very important.

Third thing is to make damn sure you have all the air out of the cooling system. It's right up there with impossible on most rotarys. Just keep working at it.

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Chris Ludwig
08 ITS RX7 CenDiv

[jake7140]

Originally posted by Newbie:
My water temp is very high...250 when running water with water wetter. It's a brand new oversized radiator, and I removed the thermostat...No fan (will an electric fan provide better cooling than air at race speed?) It cools down quickly when I back off during cool down... Any ideas on how to get it lower? Is this operating temp normnal?

Thanks,

Steve "two more races 'till I shed my X" Smyczek

Steve,
Lots of prev discusions on heat, probably in the archives.... but I believe you want to just gut the thermo and leave it in or replace it with a restrictor plate. In general, the fan does not help while at speed, at least in a first gen. a lot of first gens run sans fan. Idle/slow speed gets hot though.

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Steve
[email protected]
<A HREF="http://www.geocities.com/jake7140" TARGET=_blank>My racing page
</A><A HREF="http://www.geocities.com/elrss" TARGET=_blank>Elkhart Lake Racing_&_Sipping Society
</A>

[bill f]

My experience has been with piston engines, but the note about 'cooling temp comes down when engine speeds come down' cought my eye.

This is a very typical result when the water is moving too fast thru both the block and the radiator...it needs a restrictor in the line (or thermostat), AND reduce the rotational speed of the pump (pulley size).

One technique I use with piston engine water pumps is to block the rear face of the impeller, so the exit of the pump is radially. This is an old and new stock car trick to reduce cavitation at the pump which WILL lower the water temp.

I'd attack this problem from MANY sides, and just enjoy the results, even if you don't know exactly which one works.

Good racing.

Bill

[wlfpkrcn]

If you have not plugged the by-pass that is a must unless you gut the thermo. Also you should use a later water pump (post 82 IIRC) They are less prone to cavitation. What RPM's are you running? From my understanding with stock pulley cavitation will occur at around 8k.

Hope this helps,
Eric

[lateapex911]

plug the bypass!!!!!!!!!!!!!!

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Jake Gulick
CarriageHouse Motorsports
ITA 57 RX-7
New England Region
[email protected]

[Newbie]

Thanks all,

Bypass is plugged, and I'll be putting a restrictor in line. Makes sense that the water is going so fast that there is not adequate cooling.

I shift at 8000 rpm, so cavitation shouldn't be an issue.

I can't recall the oil temps, but they were mid gauge and I recall that as being normal. I have a new, very large oil cooler.

Thanks again, you guys are a great resource!

Steve

[dyoungre]

Is sounds like your overtemp issue will be solved, but what about the cracking? Did you put the two wafer washers behind the water pump assembly, when installing? The two bolts that crush the gasket do NOT get the washers; the washers go on the other two bolts as spacers between the water pump housing and the engine block. Your cracking could be caused by torquing it down without these parts, if you don't have them in place.

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Dave Youngren
NER ITA RX7 #61

[wlfpkrcn]

You can get an underdrive pulley to ensure the waterpump does not cavitate.

Eric

[L.Lamb]

Dave got it right. Leave the waffer washers out and the housing will break every time.....

[MaxEnergy]

Where is the thermostat bypass referred to above,located?

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Jamie Kekeisen
86 ITS RX-7 NER
92 325IS under construction

[lateapex911]

when you take off the thermostat, there is a hole beneath it. if that hole is left open, the pump will not circulate coolant thru the negine with any degree of effectiveness. In a 1st gen, you can use a big NPT plug available at the big boxes.

It doesn't need to be a perfect seal, but it needs to be secure.

(FYI) JB Weld will work for a while, but it breaks down eventually....

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Jake Gulick
CarriageHouse Motorsports
ITA 57 RX-7
New England Region
[email protected]

[jake7140]

Originally posted by lateapex911:
...It doesn't need to be a perfect seal, but it needs to be secure.

(FYI) JB Weld will work for a while, but it breaks down eventually....



So what DOES work? Solder, Lock-Tite, stake it in?

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Steve
[email protected]
<A HREF="http://www.geocities.com/jake7140" TARGET=_blank>My racing page
</A><A HREF="http://www.geocities.com/elrss" TARGET=_blank>Elkhart Lake Racing_&_Sipping Society
</A>

[lateapex911]

NPT stands for National Pipe Thread, and it's not a constant thread like a 1/4 - 20 pitch bolt. It actually tapers, like a cone. It's hard to see, but after a few turns. it gets really hard to tighten.

In plumbing (it's used for gas work IIRC) you "dope" the joints, then test with compressed air for leaks, but we don't need to worry, we just want to force the coolant into the "block", not right back into the pump!
With the thermostat out, measure the opening, and go pick up a plug that is just slightly larger, and an NPT tap to go with it. I tapped mine, then screwed it in.

I wish I could remember the size...1/2" rings a bell, but I'm not sure. It's one of those deals where you look at the size of the plug and think, "No way THATS 1/2",..." but I think it refers to the ID. In any case, it's seemed to be the most effective and secure method I found.
When the

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Jake Gulick
CarriageHouse Motorsports
ITA 57 RX-7
New England Region
[email protected]

[MaxEnergy]

Many thanks Jake. The more I think I know about these engines the less I do. I've been fighting temps for a long time on both my street cars and track car having always run them with no t-stat. I will plug that bypass today. That hole is so large I thought all the coolant went through there.

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Jamie Kekeisen
86 ITS RX-7 NER
92 325IS under construction

[lateapex911]

One caveat....I have never done this on a 13B, just a 12A, so like anything in life, confirm my advice before assuming I know what I'm talking about!

(Although I could tell you the sage of how I learned all this, but it would waste bandwidth!)

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Jake Gulick
CarriageHouse Motorsports
ITA 57 RX-7
New England Region
[email protected]

[Eagle7]

Originally posted by lateapex911:
One caveat....I have never done this on a 13B, just a 12A, ...
Same deal. I think it is 1/2" NPT.


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Marty Doane
ITS RX-7 #13
CenDiv WMR

[lateapex911]

There you have it! even confirmation on the size! A quick stop in HD or the other one and you will be amazed!


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Jake Gulick
CarriageHouse Motorsports
ITA 57 RX-7
New England Region
[email protected]