Cooling System Problem

J

Jimbob-Squarepants

Member
Hi everyone, I have what I think maybe a problem.

My cooling system seems to pressurize quite quickly without the top heater pipe getting hot. I thought Bonza, it's a blocked matrix. So yesterday I spent an hour and a half flushing crap out of it, and trying to bleed the system of air. I went for a blast and the heaters were getting warmish, but the temp gauge hardly moves (sits middle of the white bit before the green).

I have just been out in it today and the heaters have been cold and when i'm parked up, the engine smells like it's overheating, so I check the pipes and the main rad pipes are pressurized and the heater ones aren't... although the top one is now warm, but not as hot as the bottom one.

My first thoughts were a blocked heater matrix, but now I am thinking head gaskets. Of course it could be an iffy thermostat. Oh, when I run the engine without the cap on, you can see the water flowing through the top part of the rad, and it does pass some air every now and again. The coolant drops with revs, then comes back to it's level when idling.

Any advice will be very much appreciated as I don't want to scrap a nice engine.
Cheers
Jim
 
I'll go through in the order you ask.

Does it over pressurise or just build up quickly, the former will blow out coolant under the cap (so test it) the latter isn't really a problem.
Are the heater hoses fitted correctly, the top one on the engine should go to the bottom on the heater, and the top on the heater to the bottom on the engine. the latter one is the return so should be cooler than the other one.

If the gauge doesn't move check the sender and test the stat. Also make sure the bleed pipe that goes from the top of the rad to the top of the inlet manifold is clear. It blocks up where it enters the manifold.

V8's have a reputation for blowing head gaskets but it's largely unfounded. If the rad level is going down as you rev the engine, that is the way it should be, blown head gaskets start by filling the coolant with micro bubbles and then go on to blow out the coolant as you rev up.

My initial thought would be that the bleed pipe is blocked.
 
Hi Harvey, thanks for the detailed reply :D

I wouldn't say it over pressurizes as it still has alot of water in it & it would be constantly overflowing (which it isn't). It does build pressure up quickly, but it's always maintained at the same pressure if that makes sense.

I checked the heater hoses yesterday with the operations manual, and yes, they are fitted correctly. Thanks for confirming that the top one is the outlet from the matrix. I only get a trickle of water when revving if I remove the pipe.

I removed that bleed pipe yesterday as it happens (well it fell off from the manifold :roll: ). I sorted that end out by chopping it down and fitting a new Jubilee clip. I blew through the hose while it was off, and there was a nice little trickle of water coming out of the manifold while I had the rad cap off.

I will check the thermostat and temp sender when I get back outside.

One thing I did notice, the main radiator was cold all the way down. Is it possible that it could be partially blocked? Because as I say, I can see the water passing out of the top of it with the rad cap off :?

Thanks again :D
 
Jimbob-Squarepants said:
One thing I did notice, the main radiator was cold all the way down. Is it possible that it could be partially blocked? Because as I say, I can see the water passing out of the top of it with the rad cap off :?

Thanks again :D
Click to expand...

If you can feel cold spots on the rad matrix (or as you say it's cold all over) then chances are it's blocked. Only other reason could be that the engine isn't getting hot, which you say it is. It should be hot on the side where to top hose goes in, gradually getting cooler (but still hot) as it goes across and down to where the bottom hose takes it back to the engine, because in that case the rad is doing its job and dissipating the heat.
 
Thanks for your reply Harvey... I am pleased to say I have found the problem :D

At some point in the past, probably when it was last on the road (1989), some person had removed the Thermostat :roll: Now this always worries me because there must have been a reason to take it out. Anyway, I have been out to buy one, and I have fitted it.

I topped it back up with water and taken it for a drive, the heater is now warm ant the temp gauge sits at half. I am a bit silly really (on 2 counts of sillyness), because I should have checked the Thermostat first, and the engine obviously wasn't getting hot (even though it smelt like it) because it always had excellent oil pressure. Now with the Thermostat fitted, the oil light glows on idle, which says to me that it's now running at operating temperature.

I hope there has been no damage caused by having no thermostat fitted :|

Thanks again for all your help :D
 
Jimbob-Squarepants said:
Now this always worries me because there must have been a reason to take it out. Anyway, I have been out to buy one, and I have fitted it.
Click to expand...

I wouldn't worry about it.

It's probably no more than it failed to open or close properly and was just taken out as a quick fix.
 
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