octanepwr

Hi all

My FD (96) is new to me (first rotary) and I have a few questions about the cooling system. I have read a few other threads (one was called Big Fat cooling thread or something, which was good, but did not answer all my questions.)
Running a single turbo. AST removed, aftermarket Al radiator. Engine is supposedly recently rebuilt ~7000km (starts great hot/cold (harder when cold as was never tuned cold so idles low), no white smoke/steam out exhaust, no water in oil/oil in water and also running premix 150:1 Castrol TTS). Has not overheated, and by this all I can mean is the temp gauge has never got over half way

1) What are the allen key screw in things for, shown in first photo? There is three on this part (maybe this is the thermostat housing??). One as shown (wiped around it dry before photo), one on the left, and one on the back. I have the manual (summary) from this forum but it does not show details on the cooling system i.e. name parts etc. I appear to have a leak around the top one (one nearest the radiator cap), but am hesitant to undo it and try use gasket sealant etc as I may make it worse. This leak was only noticeable after a 5min idle, as I guess when up to temperature anything that leaks evaporates too fast. I have seen white antifreeze residue there before though. On other cars these screws have been bleed valves but I have never used them, as do not see the need if the radiator cap is the highest point in the system, but I may be wrong. If this screw is leaking what is my best approach to plug the hole properly? My only idea is to remove the screw, gasket sealant it, and put it back in, as tight as possible but obviously not ring the threads.

2) Has anyone ever put a aftermarket temperature probe into one of these holes? If so what thread do they use? I currently only have the standard temp gauge and have read about its lack of sensitivity which concerns me. I assume the standard gauge sender is the wire just above the top radiator hose joins the block?
I have a lot of blocked off hoses (I assume from twin turbo cooling system and AST) but there is a very short hose behind the alternator I am not sure exactly what this is for yet (photo 2. Photo 2 also shows another of these allen key screws). Can someone enlighten me? Could I possibly tee a temperature probe into this?

3) Coolant level always falls to where shown in photo 3 (p.s its not oil in the coolant, but it could probably use a flush). I am wondering if this is normal, as do not believe I could lose 100-200ml in a 15minute drive (+5 minute warmup) out of the allen key screw leak that I think I have, described above (maybe I can). Maybe it forces it out into the overflow tank - it seems not to suck it back in. I have had a new radiator cap for the last few trips and it still falls down to this level after refill and a drive.
I am going to test a new radiator overflow hose and into a juice bottle mounted so I can see if water (antifreeze) is in fact blown out and if/if not sucked back in. Maybe there is a leak somewhere in that vacuum hose as someone has jointed three pieces together - sounds rough but seems tight but I will prove this.
But I would like to know about normal coolant level in your guys experience. It doesn't take much to top up - maybe 100-200ml.
I have just been doing 'spirited' street driving only, not driven for more than 45mins or so at once yet.

4) I am using a 13psi / 0.9 bar cap (i.e. same as factory 96 cap on the AST as I understand). Someone has suggested I use a higher pressure cap (16psi) with the AST removed, but this sounds like it might cause more problems than it would solve e.g. hoses/seals going etc. From what I understand the bolt on piece I have that the cap screws to is from a S4/S5. I don't think the pressure rating of the cap is an issue, and given I have new cap, I do not think the cap is part of the issue. I may be wrong?

5) Is there an easy way to remove the coolant overflow reservoir? What is the best way to get it out?

I have lots of questions and hopefully you guys can answer some (all?)?
A+ for a numbered / well structured answer.
Thanks heaps in advance!

DaleClark

iTrader: (55)

Many good questions here.

1. Allen head plugs are from the manufacturing of the thermostat housing. Since it's a cast part, they have holes to clear out the sand from casting, then plug them. If it's leaking, remove it, clean it, wrap with Teflon tape, reinstall.

2. People have drilled/tapped the T-stat housing for a gauge, but it's dumb. You get no reading until the thermostat opens. Read this on how to plumb a temp gauge -
https://www.rx7club.com/3rd-generati...d-idea-392910/

3. Since you have that small leak at the Allen head plug, that could account for your coolant level. Don't worry about it until you fix it.

4. PSI on the cap is to increase the boiling point. If you keep your coolant temps reasonable, that shouldn't be an issue.

5. Removing the overflow tank, you have to remove the passenger wheel then the fender liner. A few 10mm bolts and it's out.

Also, the radiator cap neck you have points the overflow nipple towards the back of the car. That has the hose running fairly close to hot turbo parts, may want to un bolt it and turn it facing forwards.

Dale

ondabirdhouse

iTrader: (26)

As Dale pointed out its a bad idea to tap the T-stat housing UNLESS you put it in the back behind the Thermostat. There is a spot on the back next to the stock Temp sensor where I and a few others put our sensor.

jayscoobs

iTrader: (8)

I want to elaborate on the coolant level part of your thread as Dale covered everything. Oddly enough I recently removed my ast as well, using stock FC pressure cap. I found that my coolant is close to your level all the time now. Before It would stay closer to the top but for weeks I thought it needed more burping and kept filling it. I decided to stop adding coolant and after weeks the coolant never moved. Idk just how It is with my car car I guess.

octanepwr

Thanks for the great info guys.

I admit in previous cars I have used the top radiator hose. Therefore as noted you get no temperature on the gauge until the thermostat opens, then straight up to operating.
My hose here is a ribbed one so while this is usually a nice easy place to install (excluding the flaw), an inline housing thing would not be installable with the ribbed hose. I guess I could use two new shorter ribbed hoses.
If you keep the factory gauge though, it seems that installing an aftermarket one on the other side of the thermostat would be good enough for redundancy?
I would like to think thermostat failure rates are low if you keep clean coolant with enough antifreeze (anticorrode).

Went for a hoon today, with my juice bottle with new overflow tube, did not top up the coolant that last little bit before starting up. No overflow, no leakage from around the allen bolt, and the coolant level did not drop when inspected at the end of the drive. Therefore I agree with jay about the level being ok. (Main problem solved).

TB hose as per your write up Dale looks like I might go down this approach, but I know finding all the pipe fittings will be half a day off work haha as no place that sells them will be open weekends. I found the cooling diagram in the BIG FAT cooling thread which helps.

Thanks!