Temp gauge reads hot - car is not!

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ownatigerwishidkeptalpine
Posts: 12
Joined: Mon Jan 28, 2008 10:15 pm

Temp gauge reads hot - car is not!

Post by ownatigerwishidkeptalpine » Tue Apr 08, 2008 8:21 pm

Recently done head gaskets and ally rad as car was overheating. Rad now running cool but gauge says red hot. Tried a different gauge and temp sender, bypassed loom and wired gauge direct. Thermostat opening ok.

Any ideas?

V Mad
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Post by V Mad » Wed Apr 09, 2008 1:59 pm

There are lots of things that can cause overheating. I need to know a bit more info. You say rad is now cool; is the rad top hose hot and lower hose is cool-ish?

Do you have a stock fan with shround, or what fan are you running ?

Did you check the head gaskets are both correct way round?
Chris :-)
1966 Mk1 260 Tiger
!972 Triumph Stag 3.0V8
www.stagweber.co.uk

ownatigerwishidkeptalpine
Posts: 12
Joined: Mon Jan 28, 2008 10:15 pm

Post by ownatigerwishidkeptalpine » Wed Apr 09, 2008 10:10 pm

Hi - cant comment on hose temps as car is down local garage run by a tiger owner so he knows his stuff but is stumped by this one as is Brian Postle. I have a 5 blade ally fan and a shroud. Car was running supercool before overheat and fingers in expansion tank is bearable when car says red hot, so not hot but gauge says it is.

V Mad
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Post by V Mad » Thu Apr 10, 2008 10:47 pm

If your fan/shroud is effective then it sounds like a lack of coolant circulation; caused either by a blockage or a coolant pump problem.
Chris :-)
1966 Mk1 260 Tiger
!972 Triumph Stag 3.0V8
www.stagweber.co.uk

ownatigerwishidkeptalpine
Posts: 12
Joined: Mon Jan 28, 2008 10:15 pm

Post by ownatigerwishidkeptalpine » Sun Apr 27, 2008 10:24 am

Hi - Thanks for the reply. It seems the garage think it is not circulating properly too as top hoses hot, bottom less so. They checked the water pump and believe it is ok and refitted with a paper thin gasket rather than the thicker one that came with head gasket kit. They said it seemed to be cured as after a short drive and tickover for 20mins was maintaining temp at about 90c but to take car and drive around.
After 25mins of driving temp was about 85c - great. Let it tickover for 10mins in garage and it hit 250f!!!!!!

Block was raked out and blown out after head gaskets went, new ally rad with filter fitted, original shroud refitted and the ally fan. Hose filter checked last week and no muck or blockages, garage ran water through every hose and checked flow all seemed ok. Could there be a problem with the pump caused by the overheat? Garage was going to check impeller position and heat up with a blow lamp to see if it worked loose/had moved but I don't think there was anything wrong.

Considering just buying a new pump as there seems to be little else to try. I haven't used the car properly since it overheated July last year and I'm getting fed up with it!!!!!

V Mad
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Post by V Mad » Tue Apr 29, 2008 10:06 am

I know how you feel, but dont lose heart, the answer is there, you just have to find it. Sometimes I find I can solve things by following a hunch, but if that doesnt work I follow an elimination approach, starting with the easiest /cheapest test.

Let's consider your last experience: "After 25mins of driving temp was about 85c - great. Let it tickover for 10mins in garage and it hit 250f!!!!!!"

That seems to prove that when there is good airflow (ram effect) and the engine is revving there is no cooling problem. This means there is no blockage, and the pump works at least when the engine is revving a bit. The overheat at idle suggests that either (1) the fan/shroud is ineffective, or (2) the pump lacks something at low revs.

So, taking the first theory, how do we eliminate that? It depends on your resources; add an electric fan, or play around with the fan position, change the fan for a stock fan etc etc. The fore/aft fan position in relation to the shroud can be critical (see very detailed cooling article on Tigers United website).

Changing the pump is about all you can do to test the second theory, but make sure you use or discard the backing plate depending on manufacturers instructions. If there is too much impeller clearance the coolant will escape through the gap, more so at idle.

Finally, just to check: are you sure it is really overheating, and not just a faulty gauge/sender?

Good luck.
Chris :-)
1966 Mk1 260 Tiger
!972 Triumph Stag 3.0V8
www.stagweber.co.uk

ownatigerwishidkeptalpine
Posts: 12
Joined: Mon Jan 28, 2008 10:15 pm

Post by ownatigerwishidkeptalpine » Tue Apr 29, 2008 9:02 pm

Hi - Thanks for the advice to date.

The only thing that did ring a bell is that I recall the set up of the fan was on some spring washers and normal washers that would have had the fan slightly nearer the shroud/rad and I know the garage said they changed that set up for a better less fiddly one. This would have moved the fan back to the block by 5-8mm.

It's clutching at straws but that's the only thing I've got at present. I will fiddle with this myself tomorrow.

The garage are talking to Real Steel tomorrow to see if they have any ideas with all their yank engine experience.

Otherwise (not being a mechanic but having half an idea) I don't know how the pump can be less effective at idle now than say it was. I'm sure the fan belt isn't slipping.

Gauge has been checked against two other s/hand ones and read the same. Sender changed/and it's position changed too into a different set up using the garage mans tiger pipework/sender holder body.

He did mention something about (I think) a long shroud where the sender goes having broken or corroded away? But this could have been like it already if I'm making any sense!

Just to confirm that the car was running a new ally rad (did about 1000+ miles before it clogged up) previously without a top hose filter and with the fan/shroud on the car now. The garage said how excellent the temp was on it. The sender packed up but as car always ran cool I didn't change it in time. Got caught in heavy summer traffic and the car boiled over.

Result was head gaskets both gone. Replaced those and did all cam followers at the same time as had some sticking one's previous to overheat.

Some valves found to be bent which were machined straight. Heads didn't need skimming and were not cracked. Garage confirmed gaskets went on correct as followed instructions AND checked with Brian Postle too.

Car still ran too hot. Flushed muck out of rad but failed a flow test so bought another new ally rad but filter too this time. Car still runs too hot although I have not let it boil over since.

This leads me to the present day. I will print off the artice about shroud/fan positioning.

Cheers

H, Sunny 65
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Post by H, Sunny 65 » Tue Apr 29, 2008 11:34 pm

HI it may sound daft, but is cooling fan fitted corect way round & sucking air & not blowing ? I had similar probs & fitted latest kenlow in front of rad, i now run with out cowling and have no probs, i also only fill with distiled water & best a/freeze u can get. hope you get it sorted. regards Harry.

ownatigerwishidkeptalpine
Posts: 12
Joined: Mon Jan 28, 2008 10:15 pm

Post by ownatigerwishidkeptalpine » Wed Apr 30, 2008 7:53 am

Yes fan is correct way round.

I need to check though with garage regards spring washers as having looked this morning they may have fitted a spacer plate, can't remember if it was there before or not.

I am running 50/50 antifreeze.

ownatigerwishidkeptalpine
Posts: 12
Joined: Mon Jan 28, 2008 10:15 pm

Post by ownatigerwishidkeptalpine » Wed Apr 30, 2008 6:50 pm

Quick update - garage spoke to a chap who races three tigers who said thermostat should be changed for a 92degree one (3 litre capri spec) as coolant is running through too fast and so not cooling in rad as passing thru too quickly at idle.

Also to be on the safe side to fit an electric fan for it to cut in as necessary.

So this is being sorted and I will update once results known in a week or so.

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