kevino

-First of all, I have an 88 TII with RP downpipe, cat-back exhaust and bonez cone style air intake; everything else is factory. Here's my problem: Generally my car runs anywhere around 1/4 to 1/2 on the factory temp gauge, which I gather is pretty much normal for a TII, but when there is strain on the engine(going up a hill), when producing boost for moderate amounts of time, or when left at idle for more than five minutes the temp gauge will jump up to at least 3/4, and takes a good amount of cruising to bring it back down.

-I don't think the cooling system is to blame because I haven't found any leaks, the water pump is functioning normally, the electric cooling fan in fuctioning, thermostat is fine and inserted correctly, I have a rebuilt engine with about 5,000 miles and a new radiator(factory size).

-This is what I think may be going on: The main reason I think my engine is overheating is because of my turbo. My turbo overheats very easily (it always has a slight red glow to it, and after heavy boost it can reach bright orange), so I think it may be sending very hot intake air into the engine causing it to overheat. I have taken my turbo out recently and upon inspection I found a couple of cracks running through the turbo manifold around the region that mates with the exhaust manifold. Could these cracks be causing my turbo to overheat and thus the engine too? One other idea I have for why my engine overheats is possibly my air/fuel ratio. Could my exhaust and intake modifications be causing my engine to run lean and hot?

-Please let me know what you guys think of my ideas and please share yours as well.

-thanks
kev

RX7_ZRO

I'm nowhere near a turbo expert, but I'll offer what I can. Your intercooler, have you checked it, to see if maybe it's blocked or maybe just not cooling things down enough? Like I said, I'm no expert on turbo's I've never even seen one up close, but I know generally how they work, so maybe it's something like that. Good luck.

dr0x

Intercooler wont really affect the engine temperature. mm... i forget, there was a problem that caused the turbo to glow orange..

HeffBoost

Hmm........ Sounds like you might have the stock cat still in there somewhere? How many miles? I've heard that excessive backpressure can cause turbo overheating. Usually lean is hot from what I know. Red is fine, orange is not. Regardless I don't think that would explain your general engine overheating.

Cracks are a judgment call, you can get away with small ones. Being on the flange might be a prob. if they go clear across though. Again, not a reason for engine overheating. I've had massive exhaust leaks on my TII and the gauge did not deviate in the slightest.

Getting hot idling with (aftermarket electric fan?) on and overheating sounds like coolant system either not full, plugged up or pump not doing it's job well enough(belts tight?). The latter I wouldn't think, if everything is fairly new, including the engine itself.

How many pounds of boost are you running? Do you have an airpump or the dual pulley deal? Maybe the water pump isn't being driven good enough?

I don't know, just thought I'd throw that out there.

kevino

I don't have the factory cats in still, it's all aftermarket exhaust. I have 153,000 on my car and about 5,000 on a rebuilt engine. On the note of the turbo, there is a crack that runs the whole way through the flange. I have factory electric fan, the water pump appears to be fine with no belt slippage, and the radiator is filled right to the top.

maybe the cooling system just can't handle the upgrades

-I'm running about 8~9 psi at 6,000 rpms

-kev

SureShot

The factory fan? - You mean the little pusher on the front?
If that's all you're running, no wonder it's overheating.
Is the mechanical fan still installed also?

banzaitoyota

1.Are the Oil Cooler fins clear of debris and clean?
2.Does the Oil Cooler thermostat function properly?
3.Are the Radiator Fins clean of debris?
4.Is the Stock Bottom shroud still in place?
5.Are you running a Dual Belt Pulley on the Alt?
6.Did you install a NEW Water Pump when you installed the engine?
7.Is the bottom hose collapsing under load?
8.Did you have the Radiator and Oil Cooler cleaned and Flushed when installing the rebuild ( AS required by MOST REPUTABLE REBUILDERS)?
9. Have you verified water temps with a real gauge instead of the sock POS?
10. What ratio Coolant to Water are you running?
11. Are you running a new STOCK MAZDA OEM thermostat?
12. Mazda Rad Caps?

SureShot

Yo Banzai- great checklist..

banzaitoyota

Thanks!

BlackRx7

same thing happened to me at RX-across texas drive, I tighen the water pump belts and got a new thermostat from Advanced Auto parts, now its sitting around 1/4 all the time

banzaitoyota

BEWARE of Thermostats that are not MAZDA OEM!!!!! They have a long history of causing problems

banzaitoyota

More Stuff:

13. Stock Fan Shroud installed ( For those of you running stock Meachanical Fan)
14. Electric Fan users: Do you have a Shroud installed at all. Most installations only draaw air directly across ~60% of the available core surface area.
15. are the stock deflectors installed around the relays forward of the Readiator Core Support?
16. If 15 is a no: Do you have an plate mounted across the support to direct air-flow?
17. Install a spring in the lower rad hose to keep it from collapsing at high RPM

fiebru1119

Good checklist.. I'm going to have to bookmark this thread... ya never know

HeffBoost

That ain't it.

Wow, you're thorough Banzi, very good. I wasn't even thinking of the oil system, even though it does a great deal of the cooling - doh.

Aaron Cake

iTrader: (1)

See http://www.aaroncake.net/rx-7/cooling.htm

kevino

thanks a lot for your help guys. as mentioned your check list is very helpfull bonzi; and aaron i wish i new about that page of yours a long time ago. First off, my under belly pan got ripped off a long time ago, but i never knew the importance of it, that will be the first thing to replace. Second, my mechanical fan is old and my car does overheat at idle, so i will check that. Belt tension is good. A couple of questions though, where is the oil cooler thermostat located and how do i check it? What makes the genuine mazda thermostat so superior to aftermarket?

thanks everyone
-kev

RX7_ZRO

well ****....and I thought that shroud was just down there to keep stuff out of my motor...now I gotta replace the stupid thing (it got broke on an ice pile)....just another prob to add to my list

banzaitoyota

The oil cooler thermostat is located in the oil cooler itself. I had mine verified when the cooler was Flushed at a FAA approved repair facility.

See results here:
https://www.rx7club.com/forum/showth...=Oil+AND+flush

banzaitoyota

An additional thought:

If you have ever considered replacing your clutch engine driven fan with a FLEX-FAN........ DON'T!!!!!!!!!!!!

Here is a link to show why:

http://www.safetyandsecurity.bcit.ca...dsAutoFans.pdf

fiebru1119

Man thats scary. What type of aftermaket fans do you guys suggest?