4M overheating on freeway driving?

[76 Super Saloon]

Hi guys,

Just joined the forum - My name is Warren and I have literally just bought a 1976 Toyota Crown and absolutely love it. The car is immaculate, drives beautifully and I am really enjoying owning it.

I bought the car out of Tasmania, it arrived on Monday just gone and I've been out each night just around the local suburbs to get a bit of a feel for how the old girl goes and noticed it sits a little above half way and Hot on the temperature setting. Thought it has probably been sitting around for a while so dumped the existing coolant, completely flushed the system, changed the thermostat and filled it up with some 50/50 as outlined in my service manual.

Took it for a run down the freeway yesterday and it got awfully close to Hot so I shot off the next exit and continued to cruise around 80kms and it cooled right off?

Been reading the manual cover to cover, the book reckons it could either be faulty thermostat (sorted), faulty water pump (not sorted) or the ignition timing may be too far advanced and is causing it to run hot (not convinced this is an issue).

According to the owner, he drove it very sporadically - literally 3-5 times per year so amongst just dumping the coolant, will be doing the rest of the fluids this weekend.

Anyone had a similar issue or any ideas?

Cheers

Waz

[masterofsinanju]

You've probably got some sort of impediment to flow. You've done the thermostat, so that leaves blocked or kinked hoses/hard pipes or some issue with the radiator. Replace the hoses if you haven't already (probably due if the car has been sitting around for years). Pull the top and bottom hoses from your rad and see how much water will run through it. Of course, water pump could be borked somehow too (although you'd expect it to be weeping).

Might be worth getting a newer temp gauge just to check what your actual temps are. Old ones can be misleading.

[76 Super Saloon]

You've probably got some sort of impediment to flow. You've done the thermostat, so that leaves blocked or kinked hoses/hard pipes or some issue with the radiator. Replace the hoses if you haven't already (probably due if the car has been sitting around for years). Pull the top and bottom hoses from your rad and see how much water will run through it. Of course, water pump could be borked somehow too (although you'd expect it to be weeping).

Might be worth getting a newer temp gauge just to check what your actual temps are. Old ones can be misleading.

Thanks mate - Have purchased a new water pump, clutch fan and am going to rip the radiator out tomorrow/Friday night and have it checked out by a shop.

Appreciate your help.

Cheers

Waz

[alcyon]

Ignition timing that is too retarded or too advanced could cause overheating. I witnessed this 1st hand.

[76 Super Saloon]

Ignition timing that is too retarded or too advanced could cause overheating. I witnessed this 1st hand.

Thanks Alcyon - Will definitely check that out too.

Appreciate your input mate.

Waz

[rebuilder86]

the fact that it was fine until driven on freeway suggests the thermostat was possibly maxed out during the hot fast freeway drive.
its not a good plan to begin thinking the gauge is wrong and feel any comfort from that, because usually they fail the other way, they under read. ( wax doesnt expand anymore due to a leak or corrosion and resistance stays high; gauge reads low) And if it was reading midway between hot and normal, it may have been always overheating.
i wouldve removed the thermostat and checked the coolant flow visually in the radiator cap before buying a new pump.
u remove the t-stat, reattach housing, fill system with clean water, start car and watch radiator top tank for flow. if it overflows out the cap immediately, the radiator is too blocked. if there is little to no flow the impeller blades on pump have erroded away. if it flows nice well, u can consider the pump safe but cannot eliminate the radiator as a problem because it may be slightly blocked.
Any slight blockage does two things.
1. restricts coolant from being able to conduct heat to that blocked part of the radiator and
2. accelerates the flow of water through other unblocked sections which makes the flow too fast to successfully conduct heat into the metal for radiation. This is most pronounced during hot (high engine load) driving and higher engine rpm, where coolant is moving through radiator quickly due to the faster apinning pump.
So it has a two fold affect.
it would be wise to perform a full system flush with a "fast radiator flush" cooling system flush. these use strong acids and are not just a standard cooling system flush.
do this with ur old pump before replacing it.

[76 Super Saloon]

the fact that it was fine until driven on freeway suggests the thermostat was possibly maxed out during the hot fast freeway drive.
its not a good plan to begin thinking the gauge is wrong and feel any comfort from that, because usually they fail the other way, they under read. ( wax doesnt expand anymore due to a leak or corrosion and resistance stays high; gauge reads low) And if it was reading midway between hot and normal, it may have been always overheating.
i wouldve removed the thermostat and checked the coolant flow visually in the radiator cap before buying a new pump.
u remove the t-stat, reattach housing, fill system with clean water, start car and watch radiator top tank for flow. if it overflows out the cap immediately, the radiator is too blocked. if there is little to no flow the impeller blades on pump have erroded away. if it flows nice well, u can consider the pump safe but cannot eliminate the radiator as a problem because it may be slightly blocked.
Any slight blockage does two things.
1. restricts coolant from being able to conduct heat to that blocked part of the radiator and
2. accelerates the flow of water through other unblocked sections which makes the flow too fast to successfully conduct heat into the metal for radiation. This is most pronounced during hot (high engine load) driving and higher engine rpm, where coolant is moving through radiator quickly due to the faster apinning pump.
So it has a two fold affect.
it would be wise to perform a full system flush with a "fast radiator flush" cooling system flush. these use strong acids and are not just a standard cooling system flush.
do this with ur old pump before replacing it.

Appreciate the advice mate, slightly concerned they read under - hopefully I haven't cooked the old girl.............Can you recommend a Fast Radiator Flush to use?

[rebuilder86]

personally, i havent got much to loose as my radiator is cheap, so i ignore all the nonsense out there and use vinegar, hydrocloric acid and water just in the radiator but if not done properly this can hurt lead in the solder.
i recommend this for a full system fluah where the system is not performing as it should:
http://www.tectaloy.com.au/product/d...radiator-flush
its actually called HD2 but their online database cataloguer staff got the title wrong haha.

standard alkaline flushes are only good for routine maintenance and cleaning out sludge. solid deposits like calcium, lime, rust and other sulphides or oxides of copper and aluminium require an acidic flush. they must be rinsed out thoroughly as acids hanging around in the system can hurt soldered joins and can even unblock helpfull calcium sealed leaks.
a calcium sealed leak exists where a thread or a hose or pressed fit piece contacts the coolant chambers and weeps. The calcium eventually builds up and seals it.
thanks calcium.. thanks. a 10-20 mu ite flush will not jiggle these seals out, but if left in the system a small bit of acid will continue working its way through the calcium.
Bottom line, make sure u rinse thoroughly with tap water, and only fill with 30/70 coolant/distilled water for a 1970s vehicle.

[rebuilder86]

id say ur gauge is fine seldom do they go pear shaped. the actual bimetalic spring in the gauge can crack but then it does all sorts of strange things like indicating overheat within a minute of starting, so its possible for a gauge to overread, but not like u are describing.

[rebuilder86]

actually i forgot to mention, if the wire that goes from the gauge to the earth is getting corroded, that would give a higher reading, and if the wire from gauge to sender was corroded that would give an under reading. ive never seen either of these happen in a factory manufactured vehicle with stock gauges.

[76 Super Saloon]

actually i forgot to mention, if the wire that goes from the gauge to the earth is getting corroded, that would give a higher reading, and if the wire from gauge to sender was corroded that would give an under reading. ive never seen either of these happen in a factory manufactured vehicle with stock gauges.

Thanks for all of your help 86 - going to have a crack at the HD2 before I take it to a radiator shop!!

Keep you posted mate - fingers crossed it just has some shit in it and a proper flush will clean it out

Waz

[76 Super Saloon]

Thanks for all of your help 86 - going to have a crack at the HD2 before I take it to a radiator shop!!

Keep you posted mate - fingers crossed it just has some shit in it and a proper flush will clean it out

Waz

Well.............today did not go quite as planned............hahahaha (f#$king understatement). So fitted the new water pump, fitted the new clutch fan, filled the radiator up with the HD2 + water and went for a drive. It cooked really quickly, thought I'd get it home before it overheated and managed to split my water by pass pipe. It now has a little breather hole..................

Trying to find that part locally is going to be a punish - can get the whole thing new from US for 100ish so will give that ago and see what happens.

Just hoping I havent done any serious damage - if I have managed to f#$k the head gasket I would not be surpised.

Waz

[crownman]

Hiya can you send me a pic of the pipe you need I'm sure to have a spare

regards Steve crownman 0412 711 481 [email protected]

[rebuilder86]

hmm. its most likely that u just bought it after someone fixed a leaking head gasket with a liquid additive. There are some usless bastards out there.
now the acid has removed the stop leak.
im sorry about this, but best u get it over and done with rather than mucking around with it for weeks.

[76 Super Saloon]

Hiya can you send me a pic of the pipe you need I'm sure to have a spare

regards Steve crownman 0412 711 481 [email protected]

Hi Steve - I'll take a pic of it later today and shoot you a text! If you have the part - that would be a lifesaver!

Thanks

Waz

- - - Updated - - -

hmm. its most likely that u just bought it after someone fixed a leaking head gasket with a liquid additive. There are some usless bastards out there.
now the acid has removed the stop leak.
im sorry about this, but best u get it over and done with rather than mucking around with it for weeks.

Starting to think exactly the same mate - Had a go, it hasn't worked out as planned, time to keep moving!

Really appreciate your input buddy!!

Cheers

Waz