rb gemini running hot at freeway speed

[wango87]

Hey Ive got a 1985 rbgemini with manual transmission. When i drive it on the freeway 100kmh the temp guage continually rises to just before where it goes into the hot zone on the guage. it hasnt overheated it just runs hot and wondering if ive got a problem or this is normal on these?

I dont loose coolant, the coolant and oil dont mix, i just changed both. The thermostat is good. i flushed the cooling system with that mukout stuff from autoparts store, when i ran the hose through the radiator it seemed to flow out the other end fine. I have also changed all the cooling hoses besides the bypass hose.

The itc motor thingo on the air intake hose that controls whether exhaust air comes in the air intake or fresh air comes in seemed to be permenantly stuck so that only exhaust air comes in, so i pulled the hose that came from the air cleaner housing off it and now it just lets fresh air in. I did this because the book said it can cause it to run hotter over long periods of driving and it seems like its not working properly. so im not sure if i need to fix it properly or if the problem is something else?
it has ran hot before when i had wrong spark plugs in it but i changed them and it was good again, can there be a reason the spark plugs are stuffing up?

thankyou in advance to anyone who can help me with this

[IZU069]

Splugs stuffing up?
If oiling up, probably blowby and low compression hence bad fuel economy & performance and overheating.

AFAIK, hot RBs (& such Isuzus) do not exist...
But timing could be too retarded. Or too advanced (pinging).

The hot air intake is unlikely to cause overheating.
Gunked hoses can be a problem, but you have changed those.
But a "clean" radiator doesn't mean it is not blocked... The only "certain" cleaning is a pro-job - they remove the header tank(s) and brush through etc (usually about $80).

The pump could be corroded, or gunked. Strong enough normally, but doesn't keep up with faster speeds.

I presume you have a good oil level (near full).
And the splugs are gapped at 1.1mm, and probably NGK 6BES (I think). (IMO NGK are generally the best, and many will concur with that.)

Coolant will be hotter than plain water - especially if impeded somehow (blocked fins, weak pump).

Probably more, but just for starters....
_________________
Isuzu means a lot to me
(Caveat Emptor: But I've never owned a Gemini)

[wango87]

Hey alright I checked the plugs and the top sticky out bit is white, and there is black stuff just around the top ring. the plugs are bpr5es plugs as they specify to run it it. they are gapped at 0.8.
I have a foto but couldnt load it on here.

My fuel economy is 7-7.5l per 100km and i have full oil since i changed it 1000km ago.

The temp gauge hasnt run over the middle lately and when i drive at night in the colder air the temp stays below the middle just. Is this more likely the radiator is struggling to dissipate heat, since some of the fins are a bit corroded and fall off if i run my hand over them.

or should i change my plugs up to a 6?

[wango87]

i forgot to say it only started to get really warm when i was driving on freeway and up hills in 36-37 degree middle of day

[Mattyskeese]

If the radiators fins are crumbling off when you touch them, you might want to change the radiator. I occasionally see this on a few trucks that I work on and the only thing holding the rusted fins together are dirt and old paint.

My opinion, replace the radiator or have the core replaced since it's the most suss. If it's still overheating under load, I would then replace the water pump like IZU069 says.
_________________
Slippery when dry.

[IZU069]

Nothing wrong with your fuel economy etc - that sounds like a good engine.
Your splugs should be gapped to 1.1mm (it's an electronic ignition), but that won't (shouldn't!) cause this problem.

Matty's suggestion is good.... radiators do deteriorate.

The only way to flush a radiator is professionally. They remove the header tank(s) and wirebrush etc. A home flush may unblock some, but not all. (And just use hair shampoo - for oily hair lol - forget the flush in a can etc. (Thanks R-Bob - I used to use kero - but that's way to messy).)


FYI: My last bad overheat turned out to be radiator.
The car was purchased in Canberra and cruised to Melb @110kph without problems. Leaving for Qld, it hit the red after ~ 1hour. I stopped & removed thermostat. Then home to swap for another radiator that was ok but had been sitting for a few years. Stopped after 1 hour and added the kero. Then just pushed on stopping every hour or 2 for 1/2 an hour.
Returning home from central Qld I swapped water pumps in northern NSW. I was gonna pull the head but couldn't be bothered. The only day of non-stop driving was the last from Newcastle to Melb in 44C-37C heat.
Once home, the radiator went to my local specialist. Yep - blocked etc. They cleaned it for ~$80 and no problems since.
Whether sump-gunk had clogged both radiators is unclear, but the pro-clean would have determined blockage was the problem - not water pumps etc. Sump gunk could have been checked or cleaned by removing the lowest welsh plug.
_________________
Isuzu means a lot to me
(Caveat Emptor: But I've never owned a Gemini)

[wango87]

thanks for all the help. I called some local cooling places and they all said radiator blockage so im gonna try clean it out myself the ways you suggested, and then if it still gets hot ill take it too a shop.

With the spark plugs i just went with what the ngk webiste suggested. so because its got electronic distributor and stuff it should be gapped at 1.1?

i tihnk because its the 1985 4xc1 engine it wasnt the totally unleaded one, does that affect spark plugs?

[IZU069]

Interesting... my NGK book says 0.8mm for BP5ES for Isuzu FF Gemini 4XC1 & 4XB1. Turbo & 4XE1s are 1.1mm (and #6 heat range and resistive splugs).
The BP5ES is a non-resistive splug (ie - no "R" as in BPR5ES).


But Holden RB Gemini 1985-> is BPR5ES 1.1mm
(Note that a -11 after the splug number merely means it's "pre-gapped" to 1.1mm. -13 & -15 are 1.3 & 1.5mm etc.)

The general rule I know is 0.7-0.8mm for Kettering (points) ignitions, and 1.1mm for electronic. (Or larger for hi-compression/boost etc with CDI etc.)

It does not have to do with unleaded etc.

If your splugs look ok with the hotter 5 type (ie, BP5 - not BP6 as commonly used for G-series engines), then that's the main issue.

If you have the RB reluctor system that I am familiar with (a single-pole self contained sensor feeding an ignitor mounted inside the dizzy, and a blue ignition coil Isuzu #8344103310 or #8941417030 = NipponDenso 029700-6380 or -6060), then I'm surprised it isn't 1.1mm.
But there may be a reason. Or maybe it isn't that critical? Or maybe confusion with BP5 & BPR5 splugs....?
_________________
Isuzu means a lot to me
(Caveat Emptor: But I've never owned a Gemini)

[wango87]

Hey mate so your pretty much saying with a bpr5es, I have the wrong heat range, and it shouldnt be a ressiting plug, and it should be gapped at 1.1 not 0.8.

I looked all over ngk, denso, and bosch webite and they all say a diff plug.

But just for NGK SPARK PLUGS:
On the Australian ngk website they say i should have this one: (www.ngkspark.com.au)
1985 - 1986 Holden Gemini RB 1.5L 4XC1
Spark Plug Part No. Plug Gap
Recommended Plug BPR5ES 0.8


For ngk under the aus website for jap import it said i should have this plug:
5/85 - 3/90 Isuzu Gemini 1500 4XC1
Spark Plug Part No.
Recommended Plug BP5ES-11


Under the american ngk website they said i should have this one:
1985 ISUZU I-MARK 1.5 L4 4XC1
Spark Plug Part No. Stock No. Plug Gap Photo
Standard BPR6ES-11


As far as i know the rb gemini was an isuzu (gemini or i-mark) and was just rebadged by holden right? so like if its the same engine same year why are all these plugs different? or is it variably due to highway/city use and depending on the on the ignition setup?


The ignition setup is the coil behind the battery, going to the distributor on the battery side of the engine then with leads going to the spark plugs.
The best web pic i could find was on the website below, as far as i could say the engine bay setup looks exactly the same.
http://www.fortunecity.com/silverstone/stirling/91/engine.jpg

The engine has been rebuilt before would that possibly affect spark plug type?

Im thinking I should try put 6s with a 1.1mm gap ? would you suggest this or what do you think? also resistive or not (i dont even know what resistive is)?

[wango87]

i just saw on here under spark plug technical on ngk website

http://www.ngkspark.com.au/sparkplug_tech.php?div=mod#

under the operating temperature tab.

my plug looks like the one in the middle on the left, but mine might just be the slightest bit whiter. this says good condition?

[IZU069]

I'm not saying.....
I think I'm regurging the same info you have found....
And note my caveat/signature - I know little about Geminis...

But - yes, the RB Gemini is Isuzu...
But how much? I thought Geminis were "merely imported re-badged" Isuzu (-Bellett)-Geminis, but others made me realise the differences (thanks Poida, R-Bob, et al!)

Though I wouldn't worry too much about the stateside ('Merkan) i-Mark as they can be different engines etc etc.....


IMO the key thing is that your splugs "look good". Maybe being white they are slightly hot..... There are better pics with a greater selection. (Probably on this site somewhere... I think I've seen a repro - bit I might be confusing posters with sites...) (hic)

I reckon your splugs are nothing to worry about...
As to what I reckon, and improvements, I hope R-Bob, Poida, VirtualR, Buggzy et al can advise you....

Although timing and splugs can have a big effect, IMO your problem is more likely to be radiator etc.
But if you want to try adjusting the timing by ear... (I never use a timing light for timing - only as a confirmation)
(Retarded timing overheats. So too advanced timing, but usually way after pinging etc. Most timings err on the side of retarded as this is less destructive...)

I couldn't get the pic for your fortunecity...engine.jpg.
If it's a typical RB electronic dizzy, it should have two wires (black, and red-black) coming out to a 2-pin (spade) rectangular connector.
Later RBs had a round 2-pin (spade) connector.
All electronic dizzies have the ND blue ignition coils (albeit different part numbers) and no ignition coil ballast resistors.
_________________
Isuzu means a lot to me
(Caveat Emptor: But I've never owned a Gemini)