L24e Overheating

[wardie]

A long story.

On the weekend I went down to Temora near Wagga. Down near Yass the temp gauge started to rise so I pulled over and checked the coolant level, all OK. Kept going and noticed that the faster I went the higher the gauge read, when I slowed down it went down again. Checked coolant again, all OK. I jumped the aircon pressure switch to activate the electric fan (AC stuffed) for extra cooling and kept going.

Eventually she boiled even though I had slowed to 80 and was taking it easy up hills. I let her cool down and refilled her with premix coolant that I had bought just in case at the last stop. She stayed hot for the last 115 km. When I checked the coolant later all levels were OK. The day was hot but not over 38.

I ran some radiator flush through her and got some (not much) gunk out so did it again. This time no gunk. I filled her up with quality coolant using 50% ratio and pressure washed the AC condenser/radiator to remove any bug debris etc.

She ran hot at 100kmh untill the sun went down and then over half way for the rest of the trip. I have checked the coolant again and it is still full and clean.

Guys/Girls from all your collective experience with L motors what would be the best place to start fixing this. I thought it would be the radiator but after flushing it a few times am now not sure. Do water pumps stop pumping? I have replaced the thermostat a few months ago as the old one was stuck open. Should I pull it out so there is no restriction in the colling system.

Any advise gladly accepted.

Wardie

[blind_elk]

Water pump, in my experience, is normally not a problem in itself (only if it springs a leak through the shaft bearing / seal).

First off, I would check, and probably replace, the thermostat; it's probably not opening properly. If that doesn't work, I would suggest a proper cleanout (remove, de-tank, ream cores) on the radiator.

[V8skylineMAN]

your thermostat, she is fooked senor

[george.bryant]

yeah i had same problems, thermostat. and sometimes a brand new thermostat can be "fooked" too so if you have the same problem get another one right away.

[Cubes]

With old motors try to avoid those engine block power flushes.

From experience it dislodges crap at a later date blocking your cleaned radiator.

If you must place a stocking (old bodgy mechanics trick) over radiator water in snout then place the hose over it carefully.

No doubt the L series motors are the same as the RB's... The top rad hose is the water in, or block hot water out.

Monitor it obviously and clean until you no longer see crap caught in the stocking.

[Ghostrider]

Has been said that the thermostat isn't necessary, but my experiences tell a diferent story, but as has been said by the others, thermostats are a consumable item and can fail in a whim, so I would be looking at the thermostat first and then the water pump.

If you plan on replacing the pump check ebay, they are being sold on there for prettu good price. Search L28 for it.

If it's something that has just started and you haven't experienced this problem before, it's most likely the thermostat.

[wardie]

I pulled my thermostat out and tested it. Seemed to be OK but I did not put it back in. She runs over half still around town and I am still to try the freeway.

My brother-in-law thinks it's the viscous fan coupling thats the problem, he reckons it's too loose. How tight should they be? I would have thought that this would show up as a slow speed heat problem as I would assume that there is enough air being forced through the radiator at highway speeds.

Thanks for all the advise so far.

Wardie

[Ghostrider]

That would be correct for my money.

It's my understanding that there is more air coming onto the radiator at 30kph than the fan can suck through it.

You want to try something a bit off beat?

Try lifting the back of the bonnet about 5 or 6mm and remove the rubber seal, or better still just for the experiment, lift the bonnet about 10mm by packing the hinges with washers.

This idea is just that it should release any build up of air inside the engine compartment and actually get air flowing thru the radiator and not just hitting it.

This is a bit off beat cause your problem is just happening, I think otherwise it's a water/coolant circulation problem, maybe the fins on the pump have corroded away or are simply spinning on the shaft and not doing anything else.

A test is drop the coolant level below filler point and see if the coolant is moving underneath, it should be moving fairly fast right to left.

D

[Ghostrider]

If all is ok with the flow, try replacing the radiator cap, as if that's lost tension in the spring it's allowing the coolant past the relief and into the overflow, but you said coolant levels are fine, which should eliminate this.

If your down my way, or next weekend I might be going to Newcastle to pick up that gearbox I might be able to loan you a 1.3bar cap to play with and see what happens.

You got a small or large cap?

[Cubes]

Ghostrider,

Lifting the back of the bonnet only aids cooling at low road speeds.

The back of the bonnet/lower of the windscreen is a high pressure zone once road speeds are higher.

One reason why manufactures place air inlet vents at that location... High pressure.

As a test raise the back of the bonnet, grab a few strips of paper and sticky them on to the back of the bonnet.. Raise road speed and watch them get sucked in to the engine bay. This will be especially noticable IF you run an FMIC without boxing it off to the radiator.

[Ghostrider]

Ghostrider,

Lifting the back of the bonnet only aids cooling at low road speeds.

The back of the bonnet/lower of the windscreen is a high pressure zone once road speeds are higher.

One reason why manufactures place air inlet vents at that location... High pressure.

As a test raise the back of the bonnet, grab a few strips of paper and sticky them on to the back of the bonnet.. Raise road speed and watch them get sucked in to the engine bay. This will be especially noticable IF you run an FMIC without boxing it off to the radiator.

<{POST_SNAPBACK}>

Manufacturer's place air intakes at the front edge of a windscreen for that purpose, the high pressure zone is on top of the bonnet surface. Sure a percentage of the air will go down the the windscreen into the air intakes for the flow through ventilation, but I would beg to differ to your reasoning about the pressure under the bonnet, as all high pressure areas when travelling across a given surface create a low pressure zone under that surface.

That's simple physics!

Look at the bonnet of an R30 and the trailing edge is swept upwards.

Maybe you should pass your theories across Fred Gibson when he was racing DR30's in the 80's cause both the cars #15 & #30 had the rear of the bonnet raised to allow the engine heated air out from under the bonnet which in turn increased the airflow through the radiator, intercooler, oil cooler and engine compartment generally.

Have you done the experiment your talking about?

[Cubes]

No need to get narky..

I am no expert on physics.... I have however performed the experiment when I too was having over heating issues.

The paper was sucked backwards in to the engine bay over ~55km/h, I didn't bother running at speeds over 60km/h. It was a simple drive around the block.

I do run a 100mm bar/plate FMIC that isn't boxed off to the a/c condensor/radiator, I suspect the fmic prevents air flowing well past the radiator in to the engine bay, especially when not boxed off.

I suspect the gibson DR30's were very well boxed off so hardly comparable.

I do know the clutch fan works much harder since the fmic was fitted which is another indication there is little pressure placed upon the front of the radiator. My overheating issues were the clutch fan, it was engaging but not well enough.

100km/h would not run the car any cooler, if anything it would run a little warmer, possibly due to a higher load placed on the engine.

Without the FMIC, if it was boxed or a different front end design my findings may have been different.

Experiment and see...

[Ghostrider]

Autospeed, the online performance magazine recently did an exercise on engine compartment air pressures vs frontal and the short story result is that @ 60kph and above, the engine compartment pressure and that at the front of the car were both IDENTICAL, and therefore there was ZERO air flow through the radiator or any other unit situated at the front of the engine.

For my take on this I have louvers in my bonnet at the front and side of the engine. Something like the reverse slats in Zed car bonnets, that work on the same high/low pressure in physics.

I'm not using such a huge FMIC as most you guys, but mine is genuine HKS made for my R30 and I have been told it flows very well and capable of a lot more HP than I'm looking for. It's smaller in both dimensions, giving me space for my oil cooler on the end.

BUT this discussion is not fixing wardies problems, so don't you think getting back to and sticking to the subject at hand is the preferred choice.

D

[Cubes]

I do know the clutch fan works much harder since the fmic was fitted which is another indication there is little pressure placed upon the front of the radiator. My overheating issues were the clutch fan, it was engaging but not well enough.

100km/h would not run the car any cooler, if anything it would run a little warmer, possibly due to a higher load placed on the engine.

That last little bit........ But as stated earlier, that was with a bar/plate fmic that does block airflow to the radiator, probably very similiar to that of a badly designed front end such as a VL or 180sx.

Which remindes me, My sisters VL had an issue with cooling, at higher road speeds it too would creep temp. replaced clutch fan.. all gone.

[discopotato03]

I reckon give another viscous hub a go , for the four bolts/nuts its a quick tryout if someone has one lying around .

The debate about pressure before and inside the engine bay is interesting but airflow through the core is whats needed . I'll always stand by the engine driven fan as it pulls air through the core (and engine bay) whilever the engines running .

As for the overheating L24 , even without the thermostat its getting halfway so either the rads RS or its not getting enough air through it . I'd be getting it hot and giving it a free rev and seeing if the fan is pulling much air (free hand in front of core saves hands/fingers ) . If he likes the car he should not have a problem with getting a new or good second hand hub . If it still overheats then Id get help with the rad .

All this assumes that the head gasket is not blown or ignition timing way out or AFR way too lean . MR30's in good nick don't have cooling problems so std parts in good condition will do the job .

Cheers A .

[wardie]

Thanks All for your comments.

On the weekend I replaced the water pump ($50) and reverse flushed the radiator and the block. Didn't get any crap out. I also gave the radiator a couple of solid hits with a large rubber mallet around the frame whilst flushing it to try and jar any crap loose.

Did not make any difference at all. Still half way around town and up on the top small mark on the freeway with the A/C fan running.

I'm going to look for another fan clutch at the wreckers. How tight should they be? Is there an easy way of picking a good one? Are they cheap enough to buy new from an autoparts store?

If that does not work any one know a cheap place in Sydney to get a recore or refurb radiator?

Thanks again

Wardie

[discopotato03]

I think it may have been Davis Craig or Natra that were supplying viscous hubs but don't quote me .

I've always had great results from Southern Suburbs Radiators near the Blakehurst end of King Georges Rd . Kyle and his dad are very helpful and try hard to please . I'm sure they could advise you on hubs as well .

Another thought - it may be worth looking into the temperature probe as when they lemon out you get all kinds of strange readings . A long shot but happens at times .

Cheers A .

[wardie]

After searching around for a NEW radiator - no one make one for the R30. Pricing a recore - $360+. I decided to try some of the backyard cures for a clogged radiator.

After researching the net I decided to try using "CLR" to loosen the crud and then water and compressed air to reverse flush. I used 1/2 bottle of "CLR" and topped the radiator up with warm water (rad out of car), then left it for 15 min giving it a agitate every 5 min, making sure that the mixture filled every tube. I then reverse flushed it with large amounts of cold water. Once I saw no more foam I injected compressed air through the drain plug hole with the radiator upright. Note - make sure that the inlet port is plugged and the filler is pointing away from you or you'll get blasted!!. I let the rad fill back up after each blast. I then repeated the process with the second 1/2 bottle of the "CLR". I was not brave enough to use the full bottle in one go as it is acid based and I did not want it to chew out a soft spot.

Looking through the filler I can see that the tubes directly below it are now open. I also gave these tubes and any close by a blasting with compressed air to remove any residual crud. I don't think that I managed to totally de-crud the rad but it's a start.

I also noticed once everything was cleaned up that there was about 0.5mm of rock hard crud around the filler on the surface that the radiator cap seals to. This was letting water flow out the overflow port while I was reverse flushing with the new cap on. I scraped this away and sanded out some of the deeper scratches and now have a good seal.

I took her for a run on the freeway at speeds that would have caused her to overheat previously and she sat below 1/2 even up the hills. I still have the thermostat out but will drive her for a week and if she stays cool I'll refit t the thermostat later.

Wardie

[blind_elk]

The radiator place should have been able to do all that; and with both tanks removed. It should only need a re-core if you have corrosion. Get the radiator place to do a proper "remove end tanks, ream cores" on it.

If you can still get the engine up to temp without a thermostat, then you may still have a problem. My tame mechanic also recommends to use a genuine Nissan thermostat.

[wardie]

Due to some corrosion caused by leaf litter stuck between the condensor and the radiator the two radiator shops that looked at my rad would not rod the unit out as they were concerned about it failing and then having me harrasing them to fix it.

At this time I cannot afford to recore the unit but I need a car as I am between jobs so the backyard job.