Jump to content
Larryjc

Hot TR7V 8

Recommended Posts

I know this has been covered a lot here and I've read loads of post on various forums but my issues seems to be an odd one.  I've just bought this 7V8 with a new 3.9. I suspect it was a short engine as the front cover certainly ain't new although its clearly had a new water pump (much shinier metal). I also took out the thermostat and the centre had been removed.  So had the previous owners been chasing an overheat?  Quite possibly because the radiator had been bodge mounted to clear the front pulleys and was leaning at an angle so was probably not letting air through it properly.  I've remounted the rad properly but it is a standard TR7 one not an 8.  I checked with Ropbsport and they tell me that both rads have the same cooling capacity just different hose mounts.   Others here may know better but that's not the main problem.  I've made sure the system is filled properly - using a large funnel well above the height of all the hoses and I'm certain there is no air bubble in the top hose.  I 've fitted an 85 degree thermostat and drilled a hole in it and a Racetech electric temperature gauge (sensor in the Offenhauser manifold).  When hot, the engine runs at an indicated 95-100 degrees and the large electric fan does little to reduce this.  The heater only produces warm air not hot but as I've run race engines with the heater blanked off I don't see why this should be an issue.                                                                                                                                                                                                                                                                                                                                                                                                Now the weird bit. When it starts up it takes about 5 minutes to get to about 80 and then shoots up to 95 within about 20 seconds, presumably this is when the stat opens.  As I understand it, the closed stat keeps water circulating in the engine only but with a bypass to allow the water pump to flow which comes from the manifold to the top of the water pump and presumably also the heater circuit.  Once this water reaches the temp of the stat, the stat opens and allows water to circulate through what should be a reasonably cool radiator and hoses, hence maintaining the temp.  On other cars I've seen this as the temp comes up quickly and then stabilizes. Or even goes up and then drops slightly.  I've never seen it shoot up 15 degrees once presumably a large amount of cooler water is available.  Can anyone shine a light on this?  I've ordered a remote infra red temperature gun from good old Amazon which should allow me to track real temperatures and I'm going to try a cooler thermostat but any other ideas gratefully received.  Oh and happy Christmas to all.

Share this post


Link to post
Share on other sites

Wait until you receive your infa red temperature sensor. Brilliant tool.

Check the temp. on the rad., temp. sensor fitting and heater connection.

if your temp. gauge is correct then I would be thinking poor flow/heat dissipation, radiator, blockage - collapsed hose, pump U/S etc. or a big air lock.

Wild shot but has your Offenhauser manifold been plumbed in correctly  to pump heater etc.?

Does the water boil?

I have instances of high temperatures due to air locks.

Usually cured after running the engine a while and topping up the header tank.

Any photos of under your bonnet?

Good luck David

 

Share this post


Link to post
Share on other sites

I'll be able to answer some of those once the temp gauge arrives and I've taken the car up the road for a blast in a few days. My thoughts are that If the rad were blocked it wouldn't feel hot all over once the stat has opened.  I'm pretty sure I have no airlocks as I left the car for 24 hours with a very tall funnel filled with water so the level was at least two feet higher than any part of the system.  I also bled the pipes at each junction.  The Offy has the pipe at the back of the manifold as the supply to the heater and the return comes to the top of the water pump as per the photo.

20181221_142642.thumb.jpg.c8d10a3da1e05b6453b74f9dd3bb5ae9.jpg

What is still baffling me is why the temp goes UP when the thermostat opens the coolant circuit to the radiator.

Share this post


Link to post
Share on other sites

Hi, 

It's also worth checking that all the pipes to the water pump actually do something and are open within the pump. I had to drill one out. 

Also sometimes it's worth lifting the front of the car up to try to burp more air out. 

Does it boil up when on a run on the road? Just sitting still will obviously not give any air movement. 

 

Cheers Ian 

Share this post


Link to post
Share on other sites

Done the lifting the car thing, as I said I'm pretty certain this isn't an airlock issue.  I heard that some time in the past they issued a load of water pumps with the return pipe at the top not drilled out but it looks to me as though the pump has been replaced recently.  That said its on my list of things to check out.  Haven't been able to go on the road since I fitted and accurate temp gauge. But previously it didn't boil so I'm hopeful no damage has been done.

Share this post


Link to post
Share on other sites

The plot thickens.  I received my remote laser temperature gauge and fired up the engine this morning.  Firstly it seems the engine temp gauge is pretty accurate as its showing the same as the remote.   Before the stat opens everything makes sense.  When the stat opens the temp shoots up to 100 and thats the same as the thermostat housing.  However, the radiator whilst hot all over is down at 65 degrees except right at the top hose area where its more like 80.  So point 1 - It seems the rad is not getting the full water flow when the stat opens.

Now the really weird thing.  The heater has two pipes.  One from the back of the manifold which logically is the supply pipe.  The return pipe goes to the water pump inlet.  So why is the return pipe running 10 degrees hotter than the inlet???  I thought maybe the pipes are the wrong way round (the one from the manifold goes to the top heater pipe) but then again why should it make that much difference if the flow is the wrong way through the heater? The heater runs warm but no more than that.  For the 'return pipe' to run hotter than the supply sure means that the flow is going the wrong way. A blocked or air locked heater matrix would limit flow but not heat the water up! It seems that the heater matrix is not getting enough flow and what there is, is backwards. This could also be why the radiator is not getting any real flow. 

Someone at RPI told me that there were some water pumps made with the return hole blocked and I noticed that TR8Ian mentioned having to drill a water pump .   Ian what were the symptoms you experienced?  So I guess the next thing is to strip the pump and see if there is something odd going on there. 

Ho hum, then the car needs a new hood, new brakes and new diff so should be a busy New Year.

Share this post


Link to post
Share on other sites

Careful with these laser infrared temperatur gauges:

1. they don't measure the spot of the laser

2. They have a type of wide angle lense to "see" the infrared radiating surface

3. If you want to measure a spot, go as close as possible to that spot. More distance, more surface the lense see, like with a camera, the more inacurate the reading is. See you manual, how large the surface is, the lense sees.

extech-42545-high-temperature-infrared-t

4. You read wrong on shiny metal surfaces (see Maxwell for this). The temperature reading will be too low on bare metal surfaces. If you want to measure a shiny metal surface, stick a patch of tape (regardless what color, not transparent) on that surface you want to measure.

 

Hope this helps.

Edited by MadMarx

Share this post


Link to post
Share on other sites

does your waterpump rotate in the correct direction?

there are two types of pump, and one type is rotating the other way.

If you are running the wrong one then you won't get much flow.

 

Your pump looks like an early pump so it should be driven by a standard oldfashioned pulley belt.

Edited by MadMarx

Share this post


Link to post
Share on other sites

Hi Larry, 

I wasn't actually seeing any signs of overheating - it was just pointed out to me at Robsport at the time when I had the engine rebuild a few years ago and decided that I should replace the pump as well. 

I don't have a working temperature gauge in my car at the moment and the car seems to behave very well and didn't smell hot even on a trip to France during the summer. 

Would it be worth having further look at the radiator and perhaps back flushing the whole system. 

I do by the way run a good strong mix of antifreeze with deionized water rather than tap water. 

Good luck 

Ian

Share this post


Link to post
Share on other sites

Thanks guys.  I knew about the limitations of the laser pointer thingy.  I certainly seems to me that the flow is all wrong.  The system I have uses a standard v belt but I'm going to strip it all down and look.  I raced these engines for years in TR8s and I've rebuilt several from scratch and never seen anything like this.  I also have two cartons of radiator speed flush in the wings.

Share this post


Link to post
Share on other sites

BTW...on my 8 I have a free flow cooling system. No thermostat, no restrictor.

Share this post


Link to post
Share on other sites

My race engines always had the centre of the thermostat taken out but I also had no heater. For a road car its not really a good idea.  By the way - what is the restrictor you mention?

 

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...

×
×
  • Create New...

Important Information

Please familiarise yourself with our Terms and Conditions. By using this site, you agree to the following: Terms of Use.