Outer Limits 4x4 Board

Hey everyone,

sold my 75 series cruiser this morning and found a gq I'm keen on... However there is one thing I'm concerned about.

After driving it for about 15 mins I checked the radiator hose and there was no pressure in the system. Took the cap off and it was full, no signs of leaks, no over heating but no pressure.

Is this some bizarre Nissan thing or is something not quite right here?

No visible leaks?

What motor is it too?

TB42s have big issues with cracking heads.. repairing them isnt always the lasting option either.

Yeah no signs of leaks, radiator full just no pressure in the cooling system!

4.2 diesel in a 1989 model gq

IF you could take the cap off the engine might not have been hot yet, i've got the 89 GQ 4.2 diesel and it can take a while to heat sometimes, especially if i'm going easy on it. What was the temp guage in the vehicle sitting at?

Ok so I started the vehicle, let it idle for about 5 mins then took it for a spin. Was driving for probably 20-25 mins and about 10 mins of that was up at about 90-100 kmh.

Temp guage was sitting at what I'd imagine to be normal, about 1/3-1/2. The heater in the car worked and was blowing nice warm air.

Got back to the blokes house and popped the bonnett, squeezed the top hose and there was no pressure, took the cap off with no pop or spillage but the radiator was infact full!

The engine ran well at idle and at speeds, blew no smoke but the cooling system has me concerned!

Suggy is right in saying that the TD42's do take a while to warm up - but something is NOT right there. Did you dip your finger into the water under the cap to feel the temp?

i had this problem on my 4.2diesel mine was just a dud thermostat but it still seemed to run cool.. but also remember that the temp pick up is above the thermostat itself..so needs flow to be heated properly.. mind you the std guage is so inaccurate its not funny.. mine can read 1/2 - nothing and still be 140 on my aftermarket guage..

get a pressure test done on it..

Yeah... i might grab the pressure tester from work...

But it doesnt sound great. However I would have thought that the fact the interior heater was working well would indicate some sort of flow happening. And even with the thermostat not open there should be at least some pressure building up shouldnt there?

The thermostat only prevents/adjusts flow of water, as it heats up in the engine it will still expand and warm the rest of the system backwards.

Have I got my thinking right?

AFAIK, the thermostat is there for flow control, nothing to do with pressure. In theory, if your cooling system is full and cold, then you seal it (with the cap), then heat it to 80-90 degrees, there HAS to be a pressure build up as the fluid expands.

coxy321 wrote:AFAIK, the thermostat is there for flow control, nothing to do with pressure. In theory, if your cooling system is full and cold, then you seal it (with the cap), then heat it to 80-90 degrees, there HAS to be a pressure build up as the fluid expands.

True, except that its not the fluid that expands, its the engine block that expands and creates the pressure.

Water doesn't expand or compress.

351ciofgrunt wrote:

coxy321 wrote:AFAIK, the thermostat is there for flow control, nothing to do with pressure. In theory, if your cooling system is full and cold, then you seal it (with the cap), then heat it to 80-90 degrees, there HAS to be a pressure build up as the fluid expands.

True, except that its not the fluid that expands, its the engine block that expands and creates the pressure.

Water doesn't expand or compress.

Are you for real? If your block expands/contracts THAT much, i think you'd have more problems than just low coolant pressure.

Buggerific, have you tried a different radiator cap, or checked the spring tension in the current cap? A faulty cap could be leaking cooland into the overflow instead of holding the 10-20psi it should be.

True, except that its not the fluid that expands, its the engine block that expands and creates the pressure.

ha ha....there must be some pretty heavy steam in his bathroom!!!


as for the GQ...get it hotter, my bet is the caps dumping pressure, doubt the thermostats got a prob as said above its for flow....

regards

My td4.2 never pressurises that I have noticed, I have lived with it for years, it simply will not get hot enough (although it might when I tow but I have never needed to pop the hood while towing the boat), thermostat is good, all is good, when it does start to pressurise when not towing I will have to chase up the problem.

All sounds like the same kind of line I was thinking... The cap looked and felt pretty good but I didn't have a tester with me.

I'm looking at another patrol today so I can at least compare with that.. And I'll keep you posted with what happens with the other one!

Well boys I am now a Nissan owner! Or I will be this Sat...

Looked at this other one this morning and Gave him a deposit. The cooling system on this did pressurise unlike the other one. And everything else was excellent too.

Has the 4.2 Diesel got a timing belt or chain?

Neither, it's one of their strengths, you can almost forget about the gears.

Timing gears!? Excellent!

Picking it up tomorrow now instead of sat... Cheerin!

just get another cruiser
or do you need a patrol for the wife