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This Is Getting Ridiculous And Expensive

B0oStEr

By B0oStEr,
in General Maintenance

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B0oStEr Mentor

B0oStEr

Posted
Posted

My son crashed his r32 last year and we rebuilt it.

Last week it went to the painters and whilst driving it home the fan went through the radiator when it was given a bit of a rev (<6000rpm).

I thought that we must have missed a broken engine mount that happened in the crash so I replaced them.

Oddly enough the old ones looked ok.

I gave him the radiator out of my r32 and bought myself a Justjap one.

As a result of hitting the radiator the fan had a couple of blades bent forward so we replaced it too.

I also removed a 13mm spacer that we had put behind the fan to make it clear the i/c piping.

The i/c piping was replaced after the crash and the spacer was no longer needed anyway.

He had run the spacer for a year prior to the crash and never had a problem even though he thrashed it regularly.

We rego'd the car Friday arvo and he drove the car 300km to a mates birthday party and stayed the night.

This morning whilst driving around he gave it a bit of a rev (<6000rpm) and the same thing happened again, exact same damage, completely screwed radiator, bent fan, green stuff everywhere.

How can this happen?

Engine mounts good

Radiator securely mounted

Fan straight

At least 25mm fan to radiator clearance now that the spacer has been removed which is much more than it had prior to the crash without issues.

post-13288-1183205809_thumb.jpg

Can a fan blade flex that much or could it be something else?

B0oStEr Mentor

B0oStEr

Posted
  • Author
Posted
bent waterpump shaft that may have been damaged in the original crash?

I hadn't thought of that but thinking about it now....... I doubt it because the fan pulley appeared to be running true.

I'll have another look at it though as the fan did seem to vibrate a bit as the revs climbed.

I had put it down to the vanes deflecting as they start to pull air in.

B0oStEr Mentor

B0oStEr

Posted
  • Author
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There has been some suggestion that the motor may have bent mounts or the radiator support panel was pushed back in the original crash resulting in less than stock fan to radiator clearance.

Could someone with a 32 please measure the distance from front of the timing belt cover to the back of the fan shroud?

B0oStEr Mentor

B0oStEr

Posted
  • Author
Posted
Also check the fan viscous hub is not locked up completely, which allows the blades to flex into radiator when oversped from faulty centre.

Both 1st and 2nd fans were free spinning with slight resistance when cold.

If lockup would cause the blades to flex into the radiator wouldn't that happen whenever the motor gets hot?

RB30-POWER Mentor

RB30-POWER

Posted
Posted
Both 1st and 2nd fans were free spinning with slight resistance when cold.

If lockup would cause the blades to flex into the radiator wouldn't that happen whenever the motor gets hot?

Nah thats the thing, they never actually lock up as such, they always slip some even when hot.

The only reason I asked is I have seen the above when the hubs have actually locked (faulty). i.e they spin at full engine speed.

If you replaced the entire fan assembly not just the blades, it rules it out anyway.

B0oStEr Mentor

B0oStEr

Posted
  • Author
Posted
Nah thats the thing, they never actually lock up as such, they always slip some even when hot.

The only reason I asked is I have seen the above when the hubs have actually locked (faulty). i.e they spin at full engine speed.

If you replaced the entire fan assembly not just the blades, it rules it out anyway.

Yeah I replaced the fan and the hub as an assembly twice since the crash.

Could someone with a gtst please measure the gap between the timingbelt cover and the top edge of the radiator support panel?

Both my son's and my own 32 measure 187mm but Blind elk measured his at >197mm but his car is gts4 running rb25det if that makes any difference.

B0oStEr Mentor

B0oStEr

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My son fitted a third radiator this morning and drove the car 300km home without revving it over 3500 rpm.

I had a close look at it and measured all the clearances.

When not running. the fan is about 45 mm from the fins and about 30mm from the top tank.It looks impossible for the fan to hit the radiator as everything is firm with no abnormal movement.

All the more likely possible causes have been checked and discounted.

I think the cause isn't a simple one.

The only thing that looked a bit suss is the side clearance between the fan and the shroud is 20mm on the drivers side but is 30mm on the passengers side.

Given that when the motor torques against a load it rocks toward the drivers side which would further reduce this clearance.

The point where the side clearance is least is the same point where the leading edge of the fanblade has been driven up into the top tank.

The theory I am investigating now is whether the fans close proximity to the cowl would create a high pressure area resulting in more severe deflection of the tip of the fan blade.

To further this theory the vibration or pulsing I noticed in the fan blades when revved higher might be caused by the blades constantly being subjected to alternate high and low pressure areas as they rotate eccentric within the shroud.

Has anyone heard of anything like this before?

zebra Grand Master

zebra

Posted
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Soz to sound like a smart ass....but i would be going out and buying a thermo or 2.

Also the lower radiator mounts arnt broken are they...but by the look of the picks the fan is hitting square on....my theory was that the radiator was gettin sucked into the fan not the fan sucking itself onto the radiator...but that would mean that only the lower part of the radiator would be gettin struck....so in other words ive got nothing lol.

Andrew

tacker Mentor

tacker

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If i am not wrong the fan blades should create a area of low pressure at the front of the fan blades and the back of the radiator. I not sure that a fan blade could deflect that much to make contact with the radiator core, i tried to bend mine and could not get much more than 25mm. I have gone to thermo fans now and a electric water pumps as i broke two N1 water pumps and put the fan into the radiator, with simular results to your radiator. Could the fan have picked up some stray piece of something and put that into the radiator. Stands to reason that if you have changed nothing and it doesnt do it every time and nothing is damaged with the fan that you can see it could be a bit of crap that has got between the two. How does the fanblade tips look ? Was very little damage to mine even after its second trip into the radiator

You can fix those radiators by the way look for a produce called HTS 2000 its an aluminium solder and it works a treat, well did on mine.

  • 5 months later...
Dj laBBy Collaborator

Dj laBBy

Posted
Posted

Sorry to bring up an old thread, but how did you actually go with the prognosis??

I had the same thing happen to me.

I had no probs with the old rad i had, though a little overheating issue, so bought a brand new stock rad, then after a week or so, same thing happened, no other evidence of fan hitting the rad, so thought it was a faulty rad, got it replaced, put it in the car, took off one day, then noticed i had a small leak after work. I was able to limp it home, found the next day it didn't leak, ok no probs(prob just some gunk blocking it) drove it to work, came home and well this time you could see that the fan actually hit, a big strip of rad fins were bent. I had a small leak too, to got some epoxy stuff, and moulded it in place, no probs. Got to work ok, though just took it easy. On the way home i gave it some stick and got hard on the brakes, well going through one of the tunnels fairly slowly i saw the temp creep up, took the first exit and eventually pulled off, low and behold, rad was smashed. coolant and steam everywhere.

I checked the mounts, the torque side is fine, but compression is a little compressed, but not completely broken.

My only guess is that the engine may've moved forward and combined with the engine speed or fan speed, the blades must've flexed forward and hit the rad.

So we'll see tomorrow after i replace the engine mounts with genuine nissan mounts and a new rad if it works. I seriously hope so.

B0oStEr Mentor

B0oStEr

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It turned out to be a bent water-pump flange.

To look at it the fan didn't appear to run out.

It was checked visually three times by different mechanics and was given the ok but then it was checked out with a dial indicator with the fan removed and the water-pump flange had 0.20mm run out.

Apparently at high revs that was enough to start a vibration that caused the blades to bend an excessive amount.

A new pump and 10,000 km later no more problems.

Dj laBBy Collaborator

Dj laBBy

Posted
Posted

Shit thats interesting. Not something i would've thought of, but hey, vibrations and harmonics can do a lot of real funny things.

I replaced all the mounts and got a new rad, but this time i actually ground a curve in the leading tip of the blades, so basically if the engine does move forward, its not going to be the tip that digs into the rad. So far so good. The real funny thing is that in sydney today it was around the 30's somwhere and once i got it all sorted i took a trip along the beaches to test it all out. There was alot of stop start driving and instead of the temp going up to 80' as it used to (with a new rad) it stayed between 72-76. So was pretty happy with that. Not sure if the mod on the fan helped at all.

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