Intermittent Overheating on Turbo 1HZ Troopy

[HeathB]

Hi All,

Having a very inconsistent overheating issue with my '95 turbo 1hz. My experience so far is overheating after a while (hour+) of driving when slowing back down to city speeds from highway driving. The temps will shoot up when stopped or crawling but will suddenly drop all the way below operating temp almost at random. Once it begins the overheating process the temps won't stop spiking unless I keep the revs high when driving, same goes for once I'm back up to highway speeds in keeping higher rpm keeps the engine cool.

So far I've replaced the thermostat which was faulty and sticking. This has helped noticeably but the problem is still there. I've ordered a new fan clutch which I suspect is the reason for the engine stays cool at high rpms so fingers crossed that's the only issue.

My question is what are the chances that it's a head/gasket issue. Coolant is dumping into the overflow but only to a point but I'm not sure if that's to do with overheating, the radiator cap or that I've been mostly using distilled water until I'm confident it's fixed. No other obvious head issue symptoms, EGTs never really get above 400c, running a factory 1hd ct26 at 17psi.

My thoughts are that if it were a head/gasket issue it would be worse by now as it's done a few, unfortunately mandatory, highway runs and a significant amount of kms since the issues started. Haven't felt any performance drops either, still rips around town.

 

[Eurasiaoverland]

Using water instead of coolant is a bad idea. Coolant has a higher boiling point than water. Once you get localised boiling, those pockets of steam will have no cooling effect.

Overheating when stationary or moving slowly points to poor airflow (e.g. from a worn out clutch) or poor radiator efficiency (if the core is blocked, or it's obstructed etc).

 

[svsisu]

In addition to a new fan clutch, check your radiator to ensure it is not blocked, and do an engine coolant flush to clean out the block. A shop mixed coolant in my truck and it ruined the radiator, almost completely blocking it with sludge.

 

[duncanrm]

Make sure your new fan clutch is an Aisin brand part.. sounds like you are on the money

 

[TreadingLight]

Agree it sounds like the fan clutch, especially if it has a lot of miles on it.

Do you have an EGT gauge and intercooler?

 

[mudgudgeon]

Agree with all above.

Start with a new aisin fan clutch. Don't use a cheesy aftermarket clutch.
The fan clutch is critical to keeping temps in check at slow speeds, but at also at high speeds.

75s have a narrow front end and narrower radiator so you get less surface area on the radiator. Check to see if there's still a foam rubber seal between the radiator and the radiator support. This seal makes sure air can't escape around the radiator

Also, replace the radiator cap, again, go genuine.
They are cheap and could be part of your problem. Keeping the system pressurized raises the boiling point of water by 20⁰c or more. Higher again with coolant

Also, agree with flushing the system with a chemical flush, refill with coolant for a higher boiling point.

Do you have an aftermarket temperature gauge to get an accurate read on temps?

If you're relying on the factory dash temp gauge,l they are slow to respond. If you're seeing the factor gauge rise to the red, you've got a serious problem.

If it's a head gasket, or cracked head issue, ask if the above won't solve it.
A cheap coolant testing kit from Amazon will show up exhaust gasses in the coolant.

 

[HeathB]

Cheers everyone,

Have an EGT & Boost gauge but no intercooler, initially chose not to use one since I planned on running it at very safe levels. After doing more research I'm considering adding an intercooler but not looking for any more power. As far as my gauge reads I never let the EGTs reach 500c.

Just relying on the stock temp gauge currently, think I got lucky with my stock temp gauge having good response time but definitely looking into one now.

Ended up going for a TORA brand fan clutch from online auto parts (it's cheap but hopefully ok), definitely harder to spin by hand than the current one. Unfortunately all I could get my hands on so may get a better quality one to keep as a spare.

Should the assembly be able to spin on the belt? The belt seems to slip under very little pressure from a spanner on the bolts that mount the fan clutch to the pully. Mechanic said they tightened all the belts recently.

 

[mudgudgeon]

As far as my gauge reads I never let the EGTs reach 500c.

Is the probe for egt gauge before or after the turbo?

Ended up going for a TORA brand fan clutch from online auto parts (it's cheap but hopefully ok),

Maybe. Fingers crossed.
There's loads of examples of guys fighting with ongoing overheating issues even after replacing clutches with new aftermarket clutches. Problems are often solved with a new oem clutch.
I would say, stay suspicious of the clutch