MR2 Championship

Hi all,

After my weekend of overheating, what would you guys try first to:

a) Work out what the root cause is

b) Work out what damage has been done.

I have this weekend and next and have to hand - spare engine with run big end, new radiator.

I think I'll get on order:

Thermostat
Head gasket kit

What would be your POA?

Cheers

Pete

Pete,
I also went through this 'process' ....if it helps, this is the route I followed (after much research / advice from the forums , Rogue et al) :

1) Radiator, thermostat , flushed all system (with hose pipe). Bled repeatedly. Pressure tested system ..all ok under 'normal' running.
2) Race conditions .....towards the end of 15mins , would still overheat and blow the 'pipe' of least resistance ,...normally one of the lower rubber hoses. ..
3) This happened several times, each time refilled with water , bled the system ..and overheated on last 1-2 laps repeatedly.
4) Removed head . Skimmed at machine shop (they found evidence of 'blow thru' marks' from combustion chamber to water gallery) ..and replaced head gasket, cylinder head bolts (all std toyota items ..). Interestingly it was difficult to see any significant break up of the head gasket in the region that was blowing..
5) Raced for another 3-4 races and severe overheating at Anglesey this year.
6) Replaced block and cylinder head using a REV 4 engine from Ebay. New head gasket ...checked water pump, Thermostat (all ok) ..and new head gasket ...
7) All good to date ......

I can only surmise that during my repeated overheating sessions I had done some further 'damage / warping to the head (or block ?) and this gave up on intensive race use, and exhaust gases found their way in to a water gallery ...
Best of luck ....Know how you feel ....

have fun
Matt

Wow, thanks Matt. That's a pretty comprehensive summary. Some good info there.

Just caught the Snap-on man and am now the proud owner of an exotic 'turkey baster' and blue dye. All the techs were laughing at me as I was fleeced for £40....

Anyway, got a 'free' snap-on beenie!!!!

I'll try the combustion leak test first....

Pete

Sounds like exactly the same symtoms that I have had, other than mine boiled faster, and its a mk1. I know its not the same engine but your problem sounds very simular. It was next to impossable to tell if the head gasket had gone but as there were no leaks, I changed the thermostat and it was the same, the filler cap was releasing properly (this can be a problem if the system is very full 'cos as the water expands it will blow off hoses) and the rad' is new so not blocked,it had to be the problem. I could drive normally or let it sit and idle for as long as I liked and it was fine. Half a lap at race speed and it would boil. Pressure testing the water system showed only a tiny drop in pressure that then stoped. I have to say I was a bit stumped and really wanted it to be something other that a head gasket, so I didn't have to pull it to bits AGAIN. But as I couldn't think of anything else to try I had the head skimed and fitted a toyota gasket. Having literally just got back from testing it I can report it didn't boil. Having had a few problems of this type this season we have come to the conclusion that only toyota head gaskets will do the job. They are almost entirely coated in metal where as aftermarket ones have little thin rings around the cylinder holes. Even with a freshly skimed head the aftermarket gaskets seem to let go really fast.
I hope this gives you some ideas

Good luck!

Thanks mate. More things to consider.

Time is tight so I'm gonna check the block, swap the head of my old spun bearing engine for this overheating one, new gasket set, new radiator, check the water pump pressure test and leak test.

That should do it.

Now...where's the wallet?

OK, reconnected the bombhole blown hose (this time the return pipe as it kicks back up into the engine bay). Filled with water. Ran the car until the temp guage showed due west (about 5 mins). No temperature at all at the radiator in hose, no pressure on the hoses as I had the cap off. Put the turkey baister in the pressure cap and started pumping! No change at all to the fluid colour! No water flow to the radiator at all. And remember this is after the thermostat was held open as a mod at the track.

So took the radiator out and flushed. Just a lot of light brown water, not sludgy and not warm.

Hmmm. Left it there for the night. Still not convinced it is the head gasket. I'm falling on water pump issue at the moment.

Next chapter to follow......

Any way of testing the water pump in situ?

Thing is I've never known a water pump to fail as such. The bearings go, the seals go and they leak, but all there is inside is a sort of fan thingy. If it fell to bits or lost a vane it might block the water system but I think it would also seize up. This would be easy to check and would prob'ly make the belt shreek like hell
While fiddling with mine I was amazed how long it took for hot water to appear it the rad. Even after I had fixed it. I couldn't understand why, when it boiled in a race when I got back to the paddock and opened the bleed tap on the rad, the water that came out was stone cold???

I think what must happen is that the gasses escaping into the water system pressurise the system and push the water away from the engine so it doesn't circulate properly. The water around the engine boils and the water in the pipes and rad just sort of sits there.

Ahhhh. I see.

Well a proper run out this weekend with the new rad and a 'sniff' test after should see some gasket issue.

Tis all cutting it a bit fine!!

LuckyP wrote:
Time is tight so I'm gonna check the block, swap the head of my old spun bearing engine for this overheating one, new gasket set, new radiator, check the water pump pressure test and leak test.
:

You going for plan A?

Plan A-Z more like.

Head off the old engine is true. Gaskets/bolts/therm ordered. Waterpump off old engine good so change everything this weekend and see what happens?

Pete

OK, replaced the old radiator with a new one. Drained and flushed the cooling system - and hey presto, coolant hose into the rad heated up within a few mins (No thermostat in - well just the top/seal). Drove it to work (well I didn't) and couldn't even get it up to temp!

Then took the engine out, changed to a known, flat head, new therm, known pump, 50/50 coolant and new oil. Running now as expected.

Try as I could I can't see anything dodgy with the gasket. I'll bring it next weekend to see if anyone can see if they can spot a leak. The combustion test in the coolant for both the service test and major leak test proved negative.

Hmmm......who knows.

LuckyP rides again!!!

See you all Friday

Pete

LuckyP wrote:Try as I could I can't see anything dodgy with the gasket.

Unless its gone between the middle two cylinders, in which case it runs wierd, you never really can. Having said that maybe it was something else . . . .

Who knows?

Glad its sorted

Hi,
Just wondering how many people do experienced this overheating problem??

Regards,
Nero

I can't rember seeing or hearing about too many overheating problems during his season (other than mine !). Having said that there were perhaps six or so who have mentioned it to me over the season, who have had a prob in the past, and Robin from the 750 said he thought about 80% of DNF's (over all classes) were down to overheating!! So it can be a problem.

buba wrote:Robin from the 750 said he thought about 80% of DNF's (over all classes) were down to overheating!! So it can be a problem.

Weren't they all the same car though..? Your car...? ;o)

With the radiator at the front and engine in the middle the MR2's cooling system is a bit more convoluted than ordinary cars. It's not a problem that I would say is a particular issue with the MR2, but when there's a problem in the coolant system it can escalate quite quickly. Make sure you fit some mesh in front of your radiator at the very least.