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Terry B G
11-08-2005, 11:45 AM
The Car: 1982 280ZX Auto
The Problem:

I recently had to replace my cylinder head gasket due to a knackered radiator (also replaced).

Since the work has been done, the water temp is now fine and I'm no longer being slowly cooked on long journeys.

However, I have noticed that when I do long runs at 80 - 85 if I 'boot' it for a while the cylinder head temperature gauge shoots up to near max. If I then slow down again to about 70 (zzzzzzzz) then it falls again to acceptable levels.

Water Temp is fine, oil pressure seems fine, no other apparent problems (except a ticking from the engine - tappets??).

Is this a common problem? is there a check-list e.g.

gauge,
sensor,
rip the engine out and start again,

That you would recommend/I need to work through?

I appreciate the car only being a 3 speed will probably make it run hotter than a manual but just don't want to ignore it and find I've got a serious problem at 3 am on the M11 to nowhere.

Any helpful hints, useful suggestions would be most welcome

Thanks guys

Terry B G

Nigel Brook
11-08-2005, 12:41 PM
Terry: What's a cylinder head temperature guage? Sure you don't mean oil temperature?

pmac
11-08-2005, 02:22 PM
Water Pump?? check/replace?
Bottom rad hose collapsing partially.? Check/replace
Crud in the cylinder block? Radflush and backflush maybe try.

Terry B G
11-08-2005, 05:24 PM
Terry: What's a cylinder head temperature guage? Sure you don't mean oil temperature?
I'll take your word for it Nigel, I'm still trying to work out what that big lump of metal in the front of my car is :D :D :D

Mr.F
11-08-2005, 06:45 PM
The radiator on the auto model also contains the heat exchanger for the auto box. If the auto is slipping or generating lots of heat at higher rpm, it would be worth fitting a separate oil cooler for the auto to take this load off the engine cooling system.

Similarly, an oil cooler for the engine itself might help.

However, there is probably a fundamental underlying reason for the overheating - are you sure the cylinder head gasket is sealing OK and that there are no defects in the head face that could be allowing combustion gases into the cooling water when you push the car harder.

Nigel Brook
11-08-2005, 08:33 PM
I'll take your word for it Nigel, I'm still trying to work out what that big lump of metal in the front of my car is :D :D :DTerry:
Thats exactly what it could be if you don't want to take me seriously. A lot of people on this forum have a less than basic knowledge of how their car works and I think you'll find that 90% of my posts are offering help and assistance for their respective problems. You may not count yourself as one of them but I have no way of knowing that so I generally start with the basics.

Having established that you don't have a oil temperature guage I would first suspect the thermostat although I would have thought this was changed when your head gasket was done. Secondly have you used the heater since that work was carried out? There's the possibility of an air-lock in it preventing full water circulation. Thirdly, do you actually know the water gets as hot as you say or are you relying on the guage to tell you that? What I'm getting at is that your sensor could be lying or even your guage. Fourthly, to check that your head gasket isn't leaking run your engine with the radiator cap removed and see if there are any bubbles coming up to the radiator cap level.

Black Bug
11-08-2005, 11:39 PM
I'd've hazarded a guess at an iffy thermostat too, maybe not quite opening fully, Being the easiest thing to check. A simple test would be to remove it completely and take it for a run on your private test track to see if the higher temps reoccur. It would also seem reasonable that the garage you were unlucky enough to employed recently may have cocked that up too, and/or not bled the coolant system properly. However I happily bow to the greater knowledge available here!

Must get over to you soon for that battery so I can at least try and turn my motor over a bit before it turns in to a nice solid lump! Are you around over the weekend?

Cheers,
Rob

Terry B G
12-08-2005, 12:29 AM
Terry:
Thats exactly what it could be if you don't want to take me seriously.
Easy Tiger !!!!! :D :D :D :D I'll take any advice I can get m8. Thanks for the help and I'll keep you informed re what the problem was.

AndyMinto
12-08-2005, 01:30 PM
Terry,
If it is any consolation, I have exactly the opposite problem. Up to 2000 rpm the water temp gauge reads normal (set bang in the middle). Raise the revs above this and it falls to zero! Very weird and it has just started happening. My guess for my problem is a loose connection unless anyone knows different?